Hereditary thrombotic thrombocytopenic purpura, abbreviated hTTP, is caused by inherited defects in a gene called ADAMTS13, which carries the instructions for an enzyme with one of the most elegant jobs in the circulatory system. The enzyme patrols the bloodstream and slices up unusually long, sticky strands of von Willebrand factor, a protein that helps platelets clump together at sites of injury. When ADAMTS13 is missing or severely deficient, those ultra-large strands accumulate unchecked and spontaneously snag passing platelets, forming microscopic clots throughout the smallest blood vessels. The result is a cascade of problems: platelets are consumed faster than the bone marrow can replace them, red blood cells are sheared apart as they squeeze through partially blocked vessels, and vital organs, including the brain, kidneys, and heart, can be starved of oxygen by the clotting itself. Unlike the more common immune-mediated form of the disease, in which the body produces antibodies that disable a perfectly good enzyme, the hereditary form stems from mutations written directly into the genetic code.

The research team, led by Yeming Wan and Xiubin Guo as co-first authors with Mei Tan as corresponding author, retrospectively analyzed the clinical records, laboratory measurements, genetic testing results, family investigations, and treatment outcomes of the three pediatric patients. All three children presented with recurrent thrombocytopenia, meaning persistently or repeatedly low platelet counts, with or without hemolytic anemia, the destruction of red blood cells. These are precisely the features that make the disease so easy to mistake for more familiar conditions. The heterogeneous presentation of hTTP, the authors emphasize, is a central reason it is frequently misdiagnosed, and the consequences of that misdiagnosis can be serious, because the treatments for immune thrombocytopenia do nothing to address the underlying enzyme deficiency.

Laboratory testing told a decisive story once the right assays were ordered. In two of the three patients, designated Cases 2 and 3, ADAMTS13 activity measured below 5 percent of normal, a threshold that essentially rules out adequate enzyme function and points squarely toward either a hereditary defect or a severe immune-mediated shutdown of the enzyme. In Case 1, activity was recorded at 13 percent, though this measurement was taken after the patient had already received treatment, which may complicate interpretation of the value. Critically, testing for ADAMTS13 inhibitors, the autoantibodies that characterize the immune form of the disease, came back negative in all three children. That combination, profoundly reduced enzyme activity without any detectable inhibitor, is the biochemical signature of the hereditary form and provided the rationale for moving to genetic analysis.

Sequencing of the ADAMTS13 gene revealed three distinct variants across the three patients, and this is where the study makes its most durable contribution to medical knowledge. Two of the variants had never been reported before in the scientific literature. The first novel variant, written as c.1324 C>T, p.Gln442Ter, converts a codon specifying the amino acid glutamine at position 442 of the protein into a premature stop signal, a type of mutation that typically truncates the protein and destroys its function. The second novel variant, c.1459T>C, p.Cys487Arg, is subtler: it swaps a single amino acid, replacing a cysteine at position 487 with an arginine. Cysteine residues are often crucial for the three-dimensional folding of proteins because they form disulfide bonds that hold the molecular architecture together, so substituting a charged arginine for a cysteine can destabilize the enzyme or interfere with its catalytic machinery. The third variant, c.1192 C>T, p.Arg398Cys, had been reported previously and similarly replaces an arginine with a cysteine at position 398.

The inheritance patterns observed in the families add another layer of biological interest. Case 1 carried compound heterozygous mutations, meaning the child inherited two different defective copies of the ADAMTS13 gene, one from each parent: the novel nonsense variant p.Gln442Ter on one chromosome and the previously reported p.Arg398Cys on the other. Cases 2 and 3, by contrast, each carried homozygous mutations, meaning both copies of the gene carried the identical novel variant, p.Cys487Arg. Homozygosity for a rare disease-causing variant often raises the possibility of consanguinity in the family history, a pattern frequently seen in rare recessive disorders, and family investigations are a standard part of the workup for exactly this reason. Because ADAMTS13 deficiency is recessive, carriers with one normal copy typically produce enough enzyme to remain healthy, which is why these conditions can appear seemingly out of nowhere in a family with no prior history.

The clinical implications of the study reach well beyond the three patients described. The authors make an explicit recommendation that recurrent thrombocytopenia in children, particularly when there is a poor response to immune thrombocytopenia therapy, should prompt clinicians to consider evaluation for hereditary TTP. This is a message aimed at frontline pediatricians and emergency physicians, who are far more likely to see a child with low platelets than to suspect a defect in a single obscure enzyme. The diagnostic pathway the researchers describe, combining ADAMTS13 activity testing with inhibitor screening and confirmatory genetic analysis, is now the recognized gold standard for distinguishing the hereditary form from the immune form, and the distinction matters enormously for treatment decisions, prognosis, and family counseling.

Treatment of hereditary TTP has been transformed in recent years, although the source material for this case series focuses primarily on diagnosis rather than detailing long-term therapeutic regimens. Historically, the mainstay of care for acute TTP episodes of any cause was plasma exchange, in which the patient’s plasma, laden with ultra-large von Willebrand factor strands and deficient in functional enzyme, is replaced with donor plasma that supplies working ADAMTS13. For the hereditary form, regular plasma infusions can serve as prophylaxis, providing the missing enzyme on a scheduled basis. More recently, a recombinant form of the ADAMTS13 enzyme has been developed specifically for patients with the congenital form of the disease, offering a targeted replacement therapy that addresses the root cause rather than the symptoms. Immunosuppressive drugs, which are central to treating the immune form, have little role in the hereditary form because there is no antibody to suppress, underscoring why getting the diagnosis right is not an academic exercise but a decision that shapes the entire treatment strategy.

The study also highlights the practical value of expanding the global database of disease-causing variants. Every newly documented mutation, such as the p.Gln442Ter nonsense variant and the p.Cys487Arg missense variant reported here, improves the sensitivity of genetic screening, particularly for populations in which these variants may be enriched. For families who carry such variants, a precise molecular diagnosis enables informed reproductive planning, including the possibility of prenatal or preimplantation genetic testing. It also spares patients the ordeal of repeated ineffective treatments by closing the diagnostic loop early. The authors note that their findings provide additional clinical and genetic evidence for the molecular diagnosis of this rare disease, a modest phrasing that understates the real-world impact a confirmed genetic result can have on a family that has spent months or years without answers.

Published open access in BMC Pediatrics on 21 September 2026, the study was conducted in accordance with the Declaration of Helsinki and approved by the Ethics Committee of the Affiliated Hospital of Zunyi Medical University, with written informed consent obtained from the legal guardians of all patients. The work was supported by the Master’s Student Research Initiation Fund of the Affiliated Hospital of Zunyi Medical University and the Guizhou Provincial Program on Commercialization of Scientific and Technological Achievements. For a disease this rare, case series like this one are the primary engine of medical knowledge, accumulating patient by patient and variant by variant. Each additional documented mutation sharpens the diagnostic lens for clinicians everywhere and brings the goal of early recognition, accurate genetic confirmation, and timely, correctly targeted treatment for children with hereditary thrombotic thrombocytopenic purpura one step closer to routine practice.

Subject of Research: Genetic variants underlying pediatric hereditary thrombotic thrombocytopenic purpura

Article Title: Clinical and genetic characteristics of pediatric hereditary thrombotic thrombocytopenic purpura: a case series of two novel ADAMTS13 variants and one previously reported variant

Article References: Wan, Y., Guo, X., Tian, R., Mao, Q., & Tan, M. (2026). Clinical and genetic characteristics of pediatric hereditary thrombotic thrombocytopenic purpura: a case series of two novel ADAMTS13 variants and one previously reported variant. BMC Pediatrics. https://doi.org/10.1186/s12887-026-07704-7

Image Credits: AI Generated

DOI: 10.1186/s12887-026-07704-7

Keywords: hereditary thrombotic thrombocytopenic purpura, ADAMTS13, novel variants, pediatric hematology, thrombocytopenia, von Willebrand factor, genetic diagnosis, rare disease, compound heterozygous, homozygous mutation, misdiagnosis, BMC Pediatrics

The scale of the problem the researchers confronted is enormous. The Deafness Variation Database, or DVD, a public resource that catalogs genetic variants associated with hearing loss, contains 381,924 missense variants spread across 224 genes. Missense variants are single-letter changes in DNA that swap one amino acid for another in the resulting protein, and they are notoriously difficult to interpret. Of those 381,924 variants, 303,577—nearly four out of five—are classified as variants of uncertain significance, or VUS. A VUS is essentially a genetic placeholder: laboratory testing has detected a change, but no one can say with confidence whether it disrupts hearing or is harmless. For families, that uncertainty translates into unresolved diagnoses, ambiguous reproductive counseling, and the psychological weight of an answer that is not really an answer.

Professional guidelines from the American College of Medical Genetics and Genomics, known as ACMG/AMP, allow computational evidence to contribute to variant classification, but they leave open exactly how different lines of computational evidence should be weighed and combined. The Iowa team approached this as a formal statistical problem. They built a family of Bayesian models—probabilistic frameworks that start with a prior belief about how likely a variant is to be pathogenic and then update that belief as evidence accumulates. Each type of computational evidence, from an algorithm score to a gene-level property, contributes a quantified strength of evidence expressed in the likelihood ratios that ACMG/AMP recommendations envision. The advantage of this approach is transparency: rather than a black-box verdict, every classification can be traced to explicit, auditable numerical inputs.

The first question the researchers addressed was which of the existing variant-scoring tools deserves the most weight. They compared two widely used predictors, CADD and REVEL, using Bayesian models trained on two different reference datasets: a 2019 snapshot of ClinVar, a public archive of variant interpretations, and a set of variants already labeled within the Deafness Variation Database itself. When accuracy, sensitivity, and specificity were measured head to head, the REVEL model built on the DVD-labeled variants came out on top. That result carries a practical lesson for the field: predictors calibrated on disease-specific, curated data can outperform general-purpose scores, and evidence frameworks for hearing loss should draw on resources tailored to the genes and phenotypes actually at stake.

The team then added a second layer of evidence drawn from evolutionary biology. Genes differ in how tolerant they are to missense change: some proteins can absorb many amino-acid substitutions without losing function, while others are so finely tuned that almost any change is deleterious. Sorting the 224 deafness genes into three bins—tolerant, average, and intolerant—revealed a clear gradient in baseline risk. Variants in intolerant genes carried a prior probability of pathogenicity of 25.7 percent, more than double the 10.7 percent seen in average genes and nearly triple the 8.7 percent in tolerant genes. In other words, the same DNA letter change means something quite different depending on the evolutionary constraint of the gene it lands in, and the Bayesian framework now accounts for that context explicitly.

The most consequential innovation, however, was biophysical. Many missense variants do their damage not by sabotaging a protein’s active site directly but by destabilizing the protein’s three-dimensional fold. A protein that cannot hold its shape is typically degraded by cellular quality-control machinery or accumulates in misfolded, dysfunctional forms, and either outcome can starve the delicate hair cells of the inner ear of the proteins they need to survive and transmit sound. The researchers incorporated predicted changes in folding stability into their Bayesian model, estimating how many kilocalories per mole of destabilization each variant would impose. This protein-folding-informed model outperformed the simpler versions, and crucially it did something the score-based models cannot: it supplied a mechanistic rationale, explaining not just that a variant is likely harmful but how it would break the protein.

The numbers that emerged from this analysis are remarkable. Of the 381,924 missense variants in the database, 54,752—14.3 percent of the total—are predicted to cause modest destabilization of more than 1.0 kilocalorie per mole. A stricter threshold of at least 2.0 kilocalories per mole, indicating more severe structural disruption, captures 22,237 variants, or 6.2 percent of the database. When the analysis is restricted to the prioritized variants of uncertain significance, the fractions climb steeply: 34 percent of prioritized VUSs fall into the modest-destabilization category, and 55.8 percent fall into the severe category. Taken together, the findings suggest that protein misfolding is not an occasional curiosity among deafness variants but a prevalent mechanism, plausibly underlying a large share of hereditary hearing loss that has resisted explanation.

The framework’s power is not merely statistical. Using the protein-folding-informed model, 28,866 variants of uncertain significance reached a posterior probability of pathogenicity above 98 percent and were prioritized as likely pathogenic. From that prioritized set, the team identified twelve probands—individual patients in the database whose genetic diagnoses could be upgraded from uncertain to likely pathogenic or pathogenic. For those twelve families, computational biophysics converted an ambiguous test result into an actionable diagnosis, with implications for prognosis, surveillance, and reproductive counseling. The study also highlights two specific variants that cause clear structural disruption of their proteins, illustrating concretely how biophysical characterization can settle cases that sequence data alone leave open.

Why does the inner ear appear so vulnerable to this particular failure mode? The sensory hair cells that convert mechanical vibration into neural signals are packed with precisely assembled protein complexes, from ion channels to the tip-link proteins of the hair bundle, and many of them are long-lived and rarely replaced. A modest thermodynamic nudge toward unfolding, tolerable in a rapidly turning-over tissue, can be catastrophic in a cell that must last a lifetime. The new findings give that intuition quantitative teeth, showing that destabilization thresholds of one to two kilocalories per mole—small on the scale of protein energetics—correspond to a meaningful probability of disease.

The broader implications reach beyond deafness. Variant interpretation is the bottleneck of modern genomic medicine, and the Iowa study demonstrates a template for breaking it: combine disease-specific curated databases, gene-level evolutionary constraint, and protein-folding physics inside a transparent Bayesian framework aligned with professional guidelines. The same architecture could, in principle, be adapted to cardiomyopathies, epileptic encephalopathies, or any inherited disorder dominated by missense variation. For the hundreds of thousands of families still holding variants of uncertain significance in deafness genes, the message is one of cautious optimism: a large fraction of those ambiguities may now be resolvable, not by waiting for more families to be reported, but by calculating what the variant does to the protein it touches. Twelve diagnoses have already been changed; the framework suggests many more are waiting.

Subject of Research: Computational assessment of protein misfolding as a mechanism of hereditary deafness

Article Title: The prevalence of protein misfolding as a mechanism for hereditary deafness

Article References: Gogal, R. A., Cox, G. M., Kolbe, D. L., Odell, A. M., Ovel, C. E., McCormick, K. I., Hong, B., Azaiez, H., Casavant, T. L., Smith, R. J. H., Braun, T. A., & Schnieders, M. J. (2026). The prevalence of protein misfolding as a mechanism for hereditary deafness. PLOS Genetics, 22(9), e1012085. https://doi.org/10.1371/journal.pgen.1012085

Image Credits: AI Generated

DOI: 10.1371/journal.pgen.1012085

Keywords: hereditary deafness, protein misfolding, variant of uncertain significance, Deafness Variation Database, Bayesian model, missense variants, protein stability, ACMG/AMP guidelines, genetic diagnosis, PLOS Genetics, hair cells, variant interpretation

The biology underlying Friedreich ataxia begins with the FXN gene, which encodes frataxin, a mitochondrial protein essential for iron-sulfur cluster assembly and cellular energy metabolism. When functional frataxin falls below a critical threshold, patients develop progressive cerebellar ataxia, loss of deep sensory pathways, hypertrophic cardiomyopathy, scoliosis, and an elevated risk of diabetes. Roughly 96 percent of disease-causing alleles involve expansion of a GAA repeat in the first intron of FXN, which silences transcription without altering the protein sequence itself. The remaining 4 percent of pathogenic alleles consist of intragenic variants such as missense changes, nonsense mutations, splice variants, and deletions of varying size. Patients carrying two pure GAA expansions show a reasonably consistent relationship between the length of the shorter repeat, known as GAA1, and clinical severity, which has made genetic testing a powerful prognostic tool.

That predictability breaks down, however, in a subset of patients whose disease course is far more aggressive than their apparent repeat lengths would suggest. A recent investigation into this discrepancy uncovered a surprising mechanism: in roughly half of individuals who seemed by long-range PCR to carry two expanded alleles of the same size, one of the two alleles was not being amplified at all. The test was effectively blind to one allele, producing the false conclusion of homozygosity for identical repeats. Most of these individuals turned out to carry expanded composite repeats, complex rearranged repeat structures that evade standard amplification, but a small number harbored something even more consequential: deletions of the proximal portion of the FXN gene, encompassing the promoter and early exons, which abolish production of frataxin from that allele entirely.

The new report, led by investigators at the Children’s Hospital of Philadelphia using records from the Friedreich Ataxia Clinical Outcome Measures Study, presents the clinical features of patients carrying these covert proximal deletions alongside one expanded GAA allele. The prototypic case is particularly striking. Patient 1 was diagnosed at age six with ataxia superimposed on a pre-existing diagnosis of hypertrophic cardiomyopathy. He lost the ability to walk at age 12, developed diabetes at 13, and suffered severe vision loss at 16. Initial genetic testing had indicated that he inherited two GAA expansion alleles of similar length from his carrier parents. The unraveling of that conclusion came through his younger sister, who developed Friedreich ataxia at age 10 and was found to carry two pure GAA expansions of clearly distinct sizes, 490 and 990 repeats. The genetic mismatch between siblings who shared the same parents prompted deeper analysis.

Long-read whole genome sequencing using Oxford Nanopore Technology, confirmed by a custom PCR assay, resolved the puzzle. Patient 1 had inherited only one GAA-expanded allele; his second allele carried a de novo deletion removing the FXN promoter, exon 1, and part of intron 1. Because the deletion eliminated the sequences targeted by standard diagnostic PCR, the allele appeared simply absent from the analysis, mimicking homozygosity for two similar repeats. The contrast between the siblings is clinically dramatic: Patient 2, carrying two expanded repeats but no deletion, had a much milder course, with no cardiomyopathy and no loss of ambulation at her most recent clinic visit, while her brother with the silent deletion deteriorated rapidly through childhood and adolescence.

The researchers extended the comparison to a broader set of patients with null variants of FXN, alleles that produce no functional frataxin at all. Across sixteen patients with deletions ranging from the proximal promoter region to distal exons, and including frameshift and start codon mutations, a consistent pattern emerged. All affected individuals showed ataxia and at least mild dysarthria early in their course. Those with proximal deletions tended toward early disease onset, with cardiomyopathy and scoliosis appearing in childhood. Poor weight gain and appetite, a recognized endocrine feature of Friedreich ataxia, developed in all patients with deletions, and one patient with a small frameshift variant required placement of a gastric feeding tube for nutrition. Yet the picture was not uniformly grim: a few individuals carrying shorter GAA alleles on their second copy, including one patient with a start codon mutation paired with a repeat of only 68 triplets, remained remarkably mild, with onset as late as age 41 and none of the major complications.

To quantify the impact of null alleles, the team compared the deletion and null variant group with a large cohort of 478 patients homozygous for two expanded GAA alleles. The mean shorter repeat length was statistically indistinguishable between groups, 667 plus or minus 235 repeats in the homozygous cohort versus 734 plus or minus 228 in the deletion group, yet the clinical outcomes diverged sharply. Patients with null variants had a lower average age of onset, 8.3 years versus 12 years, and dramatically higher rates of cardiomyopathy, 93 percent versus 61 percent, a difference that reached statistical significance. Age at death also differed significantly, with 32 percent of the deletion group deceased compared with 9 percent of the homozygous repeat group. Trends toward more frequent diabetes, scoliosis surgery, and vision loss from optic neuropathy were also observed. The conclusion is inescapable: a null allele, which contributes no frataxin whatsoever, produces a more severe phenotype than a second expanded repeat, which still permits a trickle of residual gene expression.

These findings carry a direct message for clinical practice. Patients who appear by commercial testing to carry two identical expanded alleles but who show an unexpectedly severe, even if otherwise typical, Friedreich ataxia phenotype should be evaluated further for an undetected deletion. Conversely, patients with one expanded allele, one apparently normal allele, and a severe phenotype should prompt a search for a null non-GAA variant, while a single expanded allele with a normal second allele and an atypical phenotype more often points toward a missense variant, though exceptions exist. The diagnostic gap exists because standard PCR-based assays target sequences within the proximal gene that are precisely the regions missing in these covert deletions. Long-read whole genome sequencing, which can traverse the entire locus and reveal structural rearrangements, proved essential for detection, and the authors demonstrated that a targeted custom PCR assay can confirm the findings once the deletion is known.

Beyond diagnosis, the study refines the statistical architecture of Friedreich ataxia prognosis. Conventional severity models treat GAA1, the shorter of the two expanded repeats, as the primary determinant of disease course, and for good reason: GAA1 length alone accounts for an R-squared of roughly 0.4 to 0.5 in predicting various clinical parameters, because it best indexes residual FXN transcription. GAA2, the longer repeat, is usually omitted from models because its values are correlated with GAA1 and its independent contribution is difficult to isolate. The new data suggest that in extreme cases, particularly when one allele is a complete null, GAA2 length can further refine severity predictions, explaining some of the variance that GAA1 alone leaves unaccounted for. Patient 11, with a 68-repeat allele paired with a null variant and a remarkably mild course, illustrates how much protective information a short second allele can carry even when its partner produces no protein at all.

The broader significance of this work extends to the growing recognition that Friedreich ataxia is more genetically heterogeneous than standard testing implies. As long-read sequencing becomes more accessible, previously invisible structural variants such as composite repeats and proximal deletions are likely to be uncovered in increasing numbers, reshaping prevalence estimates and improving the accuracy of genetic counseling for families in which recurrence risk depends on knowing exactly what each parent carries. For patients, an accurate molecular diagnosis is the gateway to emerging therapies, including frataxin-enhancing compounds and gene-based approaches currently in development, many of which assume intact target sequences within the FXN gene. Knowing whether a patient’s second allele is a long repeat or a deletion may ultimately influence which therapeutic strategy is appropriate. What began as a puzzling discrepancy between two siblings has exposed a systematic blind spot in Friedreich ataxia genetics, one that the field can now begin to correct.

Subject of Research: Covert proximal FXN gene deletions in compound heterozygote Friedreich ataxia patients

Article Title: Compound Heterozygote Friedreich Ataxia Patients With Covert Proximal FXN Gene Deletions

Article References: Lazaropoulos, M. P., Devore, M. C., Lam, C., Park, C., Bidichandani, S., & Lynch, D. R. (2026). Compound Heterozygote Friedreich Ataxia Patients With Covert Proximal FXN Gene Deletions. Annals of Clinical and Translational Neurology, 13(10), 2134-2137. https://doi.org/10.1002/acn3.70408

Image Credits: AI Generated

DOI: 10.1002/acn3.70408

Keywords: Friedreich ataxia, FXN gene, frataxin, GAA repeat expansion, genetic testing, long-read sequencing, compound heterozygote, gene deletion, cardiomyopathy, ataxia, null variants, genetic diagnosis

The acute crisis, physicians concluded, was an episode of acute kidney injury superimposed on advanced, previously unrecognized chronic kidney disease, precipitated by the dehydration of her gastrointestinal illness. She had never undergone renal ultrasound, biochemical kidney function testing, or assessment of her estimated glomerular filtration rate, because she had never before sought medical care for her underlying condition. The case, published as a case report in Clinical Case Reports, documents how a rare multisystem genetic disorder called Bardet–Biedl syndrome went entirely undiagnosed into adulthood, allowing progressive kidney damage to accumulate unchecked until a routine infection brought the hidden disease to the surface.

Bardet–Biedl syndrome is a rare autosomal recessive ciliopathy, meaning it arises from defects in the primary cilium, a tiny antenna-like organelle that projects from nearly every cell in the body and coordinates crucial developmental and signaling pathways. The syndrome is defined by a constellation of features: rod–cone dystrophy of the retina that typically begins as night blindness and progresses to blindness, central obesity, extra fingers or toes known as polydactyly, intellectual disability, hypogonadism or genitourinary anomalies, and kidney involvement. Because the condition shows variable penetrance, its presentation can differ dramatically even among siblings in the same family, complicating recognition. In European outbred populations, prevalence is estimated at roughly one in 125,000 to one in 160,000 people, but isolated communities with founder mutations can carry far heavier burdens, most famously the Faroe Islands, where a single BBS1 splice-site mutation produces a prevalence of one in 3,700.

The patient in Lahore carried nearly the full textbook picture. Blind since age 19 after night blindness first appeared at age 8, she had a body mass index of 29, primary amenorrhea, childhood intellectual disability, bilateral polydactyly of both hands and feet, widely spaced eyes, strabismus, and a history of cystostomy for urethral stricture. Two of her siblings were affected by a similar constellation of problems, and she was born to first-cousin parents, a consanguinity pattern that dramatically raises the probability of homozygosity for recessive disease alleles. Laboratory workup added further findings: severe macrocytic anemia with hemoglobin of 6.8 g/dL, elevated alkaline phosphatase at 480 U/L, and an HbA1c of 8.2 percent with random glucose of 250 mg/dL, indicating poorly controlled diabetes mellitus that had also escaped prior diagnosis.

Imaging sealed the clinical picture. Abdominal ultrasound showed coarse liver echotexture, mild splenomegaly, and kidneys with increased echogenicity and reduced corticomedullary differentiation, hallmarks of chronic parenchymal damage. Computed tomography of the kidneys, ureters, and bladder then demonstrated bilaterally small kidneys, the right measuring 83 by 27 millimeters and the left 83 by 33 millimeters, with lobulated, irregular cortices consistent with longstanding scarring. In a young adult, kidneys of this size and texture represent years of accumulated nephron loss. The combination of retinal dystrophy, kidney disease, polydactyly, obesity, intellectual disability, primary amenorrhea, and affected siblings pointed decisively toward a hereditary ciliopathy, and the principal differential, Alström syndrome, was excluded because it does not typically involve polydactyly or intellectual disability. A clinical diagnosis of Bardet–Biedl syndrome was made, though genetic confirmation was not pursued because of resource limitations.

At the molecular level, BBS is strikingly heterogeneous: at least 26 genes have been identified, most encoding proteins essential for ciliary assembly and intracellular trafficking. Disruption of ciliary signaling, including the non-canonical Wnt pathway, is implicated in the cystogenesis and progressive nephron loss that characterize BBS-related kidney disease. Genotype–phenotype studies suggest that patients with variants in chaperonin-like genes such as BBS6, BBS10, and BBS12 tend to develop more severe chronic kidney disease than those with BBS1 variants, a finding that could eventually guide how intensively clinicians surveil renal function once sequencing becomes accessible in settings like Pakistan. Diagnostic criteria originally proposed by Beales and colleagues require either four primary features or three primary features plus two secondary ones, and a recent European Reference Networks consensus has updated the framework to incorporate molecular diagnosis alongside clinical findings. This patient fulfilled the primary criteria of rod–cone dystrophy, postaxial polydactyly, obesity, intellectual disability, genitourinary anomalies, and renal dysfunction.

What makes the case exceptional is timing. The mean age of clinical BBS diagnosis is around nine years, yet this patient reached her third decade without a formal syndromic diagnosis of any kind. Renal involvement affects more than half of BBS patients and is the leading driver of premature mortality in the syndrome, ranging from structural anomalies such as fetal lobulation and increased parenchymal echogenicity to cystic dysplasia and progressive loss of glomerular filtration. In the largest reported cohort, kidney failure requiring renal replacement therapy occurred in roughly 6 percent of adult and 5 percent of pediatric patients, and affected children tend to follow one of two trajectories, either developing severe chronic kidney disease early or remaining comparatively spared through childhood. An early warning sign, reduced urinary concentrating capacity producing polyuria and polydipsia, reflects tubular dysfunction tied to disrupted ciliary signaling and can flag declining renal function years before crisis.

Treatment of the acute episode followed standard nephrology practice. The patient received three sessions of hemodialysis, broad-spectrum antibiotics, intravenous fluids, and antipyretics, and improved over subsequent days with a notable recovery of urine output before discharge with strict follow-up advice. Her echocardiogram was normal, reassuring given that cardiovascular abnormalities have been documented in a subset of BBS patients. Longer-term management of the syndrome demands a genuinely multidisciplinary approach spanning nephrology, ophthalmology, endocrinology, genetics, and cardiology, with regular blood pressure monitoring, annual ophthalmologic evaluation, and periodic assessment of renal and metabolic parameters. Should her kidneys progress to outright failure, renal transplantation remains viable with outcomes comparable to the general population, although coexisting obesity can complicate both pre-transplant workup and post-transplant metabolic management. No disease-modifying therapy yet exists for the renal or retinal manifestations, making surveillance the principal tool for delaying irreversible complications.

The Pakistani context adds a public-health dimension. Roughly half to two-thirds of marriages in the country are consanguineous, most commonly between first cousins, a pattern that should, in principle, elevate the prevalence of autosomal recessive disorders like BBS. Yet reported Pakistani cases remain scarce, a paradox the report’s authors attribute to underdiagnosis rather than genuinely low prevalence, driven by limited access to ophthalmologic, nephrologic, and genetic testing. A recent case series from Multan described four affected individuals from two sibling pairs, illustrating both marked intrafamilial variability and diagnostic delay, and the literature now includes scattered reports from Dera Ismail Khan, Peshawar, Karachi, and Islamabad. Most patients present in childhood or adolescence with retinal and developmental features and are diagnosed clinically rather than genetically, and the present case appears to be among the few from Pakistan in which unrecognized chronic kidney disease progressed to acute kidney injury in adulthood before the underlying syndrome was ever identified.

The broader lesson reaches beyond one hospital ward. Bardet–Biedl syndrome’s features can appear so scattered across specialties, an eye problem here, extra digits there, obesity and developmental delay elsewhere, that no single clinician assembles the full picture until something acute forces the issue. Greater awareness among pediatricians, ophthalmologists, and family physicians, combined with systematic renal surveillance of children showing the syndrome’s cardinal features, could allow earlier diagnosis and potentially forestall exactly the kind of delayed, dramatic presentation seen in Lahore. Genetic counseling remains central to comprehensive care, informing families about recurrence risk and the value of screening apparently healthy relatives for subclinical complications. For this 27-year-old woman, the gastroenteritis that nearly overwhelmed her kidneys also finally gave her disease a name, and with it, at last, the possibility of coordinated care.

Subject of Research: Bardet–Biedl syndrome presenting as acute kidney injury on undiagnosed chronic kidney disease in a young adult

Article Title: Bardet–Biedl Syndrome Presenting With Acute Kidney Injury Revealing Previously Undiagnosed Advanced Chronic Kidney Disease in a Young Adult: A Case Report

Article References: Abbas, A., Amjad, N., Mufti, A. F., Waqas, M., Iqbal, M., Ali, H., Habib, A., Samadi, Y., & Haider, M. U. (2026). Bardet–Biedl Syndrome Presenting With Acute Kidney Injury Revealing Previously Undiagnosed Advanced Chronic Kidney Disease in a Young Adult: A Case Report. Clinical Case Reports, 14(10), Article e73672. https://doi.org/10.1002/ccr3.73672

Image Credits: AI Generated

DOI: 10.1002/ccr3.73672

Keywords: Bardet-Biedl syndrome, ciliopathy, acute kidney injury, chronic kidney disease, polydactyly, rod-cone dystrophy, consanguinity, Pakistan, hemodialysis, genetic diagnosis, primary cilium, rare disease

The biology behind spinal muscular atrophy explains why this region has long frustrated diagnosticians. The disease is caused by loss or mutation of the SMN1 gene, which encodes a protein essential for the survival of motor neurons. Humans, however, carry a nearly identical backup copy called SMN2, distinguished by a single nucleotide change at position c.840 in exon 7. That one base difference alters how SMN2 pre-messenger RNA is spliced, so most SMN2 transcripts are translated into a truncated, unstable protein that is rapidly degraded. Each SMN2 copy produces only about ten percent of the functional protein generated by SMN1, and the proportion varies across tissues. Because the two genes are more than ninety-nine percent identical, distinguishing them requires reading across the entire roughly 28.5-kilobase locus, something short-read sequencing struggles to accomplish reliably.

Traditional testing reflects these limitations. Quantitative PCR can detect homozygous deletions of SMN1 exons 7 and 8, the molecular signature of most SMA cases, but it cannot report precise copy numbers or identify point mutations. Multiplex ligation-dependent probe amplification, or MLPA, reliably measures SMN1 and SMN2 copy numbers and detects exon rearrangements, yet it cannot resolve haplotypes or sequence-level variants. Neither method can determine whether a person with two SMN1 copies carries both on one chromosome or one on each, a distinction that matters enormously for reproductive risk. A so-called 2+0 silent carrier, with both copies on a single chromosome, appears normal on standard screening but faces the same one-in-four chance of having an affected child as a classic 1+1 carrier when paired with another carrier.

Single-molecule real-time sequencing sidesteps these obstacles through sheer read length. In the new study, researchers at Zhangzhou Municipal Hospital extracted genomic DNA from peripheral blood, amplified the full-length SMN1 and SMN2 genes together with their downstream regions using long-range PCR, and ligated the amplicons into dumbbell-shaped SMRTbell libraries. These libraries were sequenced on a Sequel II CNDx platform in circular consensus sequencing mode for thirty hours, generating high-fidelity reads that span the entire locus. Because each read covers the whole gene, the c.840 site unambiguously labels each molecule as SMN1 or SMN2, allowing the software to count copies of each gene separately and scan for point mutations at the same time. The technology carries no GC bias and handles the highly repetitive sequence architecture of this region that defeats shorter reads.

The clinical validation was striking. Among the 771 screened individuals, SMRT sequencing and qPCR produced fully concordant results in one hundred percent of samples. The most common genotype was two copies each of SMN1 and SMN2, found in 55.25 percent of participants, followed by a 2:1 ratio in 29.44 percent. Two SMN1 copies were present in 91.18 percent of the cohort, but the distribution revealed important outliers: 2.33 percent of individuals carried only one SMN1 copy and were classified as deletion carriers, yielding a carrier frequency of 2.33 percent, consistent with previously reported rates of 1.2 to 2.2 percent in Chinese populations. More provocatively, 6.36 percent carried three SMN1 copies and one individual carried four, indicating that at least two SMN1 genes sit on a single chromosome in these people, a configuration that standard qPCR cannot distinguish from the benign two-copies-on-two-chromosomes arrangement.

That finding carries direct reproductive consequences. Individuals with elevated SMN1 copy numbers may be silent carriers whose risk is invisible to conventional screening, since qPCR reports only total copy number without allele distribution. The study authors note that definitive assignment of 2+0 status still requires family-based haplotype phasing and pedigree analysis, which lay beyond the scope of the current work. Even so, the results underscore a hidden reservoir of reproductive risk in the general population. With roughly one in fifty people in many populations carrying an SMN1 deletion, and couples who are both carriers facing a one-in-four chance of an affected child in each pregnancy, carrier screening has become a public health priority, and the accuracy of that screening depends entirely on the resolution of the underlying technology.

The study also catalogued the distribution of SMN2, the modifier gene that shapes disease severity. Two copies of SMN2 were the most common configuration at 57.59 percent, one copy accounted for 33.07 percent, and small fractions of individuals carried three or four copies. Notably, 6.10 percent of the screened population carried homozygous SMN2 deletions, a genotype that is not itself disease-causing but eliminates the compensatory buffer that SMN2 provides. Because SMN2 copy number is inversely related to clinical severity in SMA patients, knowing a patient’s SMN2 count helps predict disease course and informs treatment decisions, particularly now that disease-modifying therapies exist for a condition that was, until recently, essentially untreatable.

Four qPCR-confirmed SMA patients served as independent validation cases, and their stories illustrate both the technology’s power and the disease’s variability. Patient 1, a 16-year-old female with severe scoliosis who first showed hand tremors at twelve months, had zero copies of SMN1 and three copies of SMN2 confirmed by all three methods, consistent with SMA type II. Patient 2, a 12-year-old male unable to walk independently at seventeen months, showed the same molecular profile with profound proximal weakness and absent reflexes, also diagnosed as type II. Patient 3, a 17-year-old male with flexion contractures, generalized hypotonia, and complete lower limb paralysis, carried zero SMN1 copies and three SMN2 copies but was classified as type I. Patient 4, a three-month-old male with hypotonia since birth, had zero SMN1 copies and two SMN2 copies, with electromyography revealing nerve fiber damage across multiple limbs, confirming type I disease. No pathogenic point mutations were detected in any patient.

The discordance among patients sharing three SMN2 copies is scientifically telling. Three of the four patients carried the same SMN2 count yet spanned two clinical types, echoing a large analysis of 1,627 SMA patients with three SMN2 copies in which fifteen percent had type I disease, fifty-four percent type II, and thirty-one percent type III. The relationship between copy number and severity is clearly not a simple inverse correlation; even among patients with four or five SMN2 copies, one and five percent respectively still develop type I disease. Whether different SMN2 variants possess distinct functional properties, or whether modifying mutations within SMN2 influence its compensatory capacity, remains an open question that the authors flag for future investigation.

The study’s limitations are candidly acknowledged. Point mutations in SMN1 account for roughly two percent of SMA carrier alleles, yet none were detected in this cohort, a result that may reflect their genuine rarity or a sample size insufficient to capture such infrequent events. Larger-scale studies will be needed to validate the technology’s performance on rare genotypes. Nevertheless, the trajectory is clear: SMA genetic testing has evolved from single-site detection toward whole-gene, haplotype-level analysis, and long-read sequencing has already matured into clinical practice for other monogenic disorders such as thalassemia and congenital adrenal hyperplasia. With its ability to resolve copy numbers, haplotypes, and point mutations in a single assay across one of the human genome’s most treacherous paralogous regions, single-molecule real-time sequencing appears poised to become a cornerstone of SMA diagnosis, carrier screening, and genetic counseling, potentially catching silent carriers that today’s methods routinely miss.

Subject of Research: Clinical application of single-molecule real-time long-read sequencing for spinal muscular atrophy diagnosis and carrier screening

Article Title: Clinical Practice of Single‐Molecule Real‐Time Sequencing in the Diagnosis of Spinal Muscular Atrophy

Article References: Wei, H., Zheng, Y.-W., Zhang, N.-K., Gao, T.-L., Zheng, J.-X., Li, T.-Y., & Hong, S.-R. (2026). Clinical Practice of Single‐Molecule Real‐Time Sequencing in the Diagnosis of Spinal Muscular Atrophy. Molecular Genetics & Genomic Medicine, 14(10), Article e70314. https://doi.org/10.1002/mgg3.70314

Image Credits: AI Generated

DOI: 10.1002/mgg3.70314

Keywords: spinal muscular atrophy, SMRT sequencing, SMN1, SMN2, long-read sequencing, carrier screening, genetic diagnosis, copy number variation, qPCR, MLPA, motor neuron disease, genetic counseling

The study, published in BMC Pediatrics, was led by a team at the Women and Children’s Medical Center of Shenzhen Maternity and Child Healthcare Hospital affiliated with Southern Medical University. The investigators started with an unusually complete dataset: 2,652 deaths of children under five years of age recorded in Shenzhen between January 2016 and December 2023. From this mortality cohort, they applied prespecified, record-based cause-of-death exclusions and removed deaths occurring within 72 hours of birth, reasoning that very early neonatal deaths typically involve distinct clinical circumstances and are less likely to reflect undiagnosed metabolic disease. That filtering left 1,982 children eligible for metabolic investigation.

The critical resource was the archived dried blood spots, the small cards of filter paper collected from nearly every newborn in China as part of routine screening programs. These spots preserve a biochemical snapshot of the infant’s blood in the first days of life. Dried blood spots were available for 652 of the eligible children, and the team analyzed each one for 43 metabolites using tandem mass spectrometry, a technique that can precisely quantify tiny amounts of amino acids, acylcarnitines, and other small molecules in a single rapid run. The screening panel was designed to flag 48 different conditions, using both individual metabolite concentrations and prespecified metabolite ratios, since ratios often discriminate true disease from benign variation more reliably than any single value.

Tandem mass spectrometry works by ionizing the compounds extracted from the blood spot and then sorting them by their mass-to-charge ratio in two sequential stages, which allows the instrument to distinguish closely related molecules such as the various acylcarnitines that accumulate when fatty acid oxidation is impaired. When a fatty acid oxidation enzyme is deficient, the body cannot efficiently break down fats for energy, and specific intermediate acylcarnitines build up in the blood in characteristic patterns. Elevated concentrations of these markers, or abnormal ratios between them, serve as biochemical fingerprints of the underlying enzymatic block. In this cohort, 50 of the 652 tested children were flagged as positive by the MS/MS panel, a striking yield given that none of them had received a metabolic diagnosis before death.

To determine whether these biochemical signals reflected genuine disease, the researchers turned to whole-exome sequencing, a next-generation sequencing approach that reads the protein-coding regions of all roughly 20,000 human genes. Because most known inborn errors of metabolism are caused by variants in genes encoding enzymes, transporters, or cofactor proteins, the exome captures the great majority of the relevant disease space. The team sequenced all 50 MS/MS-positive cases and interpreted the variants according to American College of Medical Genetics and Genomics and Association for Molecular Pathology criteria, the standard framework for classifying sequence variants as pathogenic, benign, or uncertain.

The molecular work delivered definitive answers in 13 of the 50 cases, or 26 percent. Twelve of these were inborn errors of metabolism, and one child turned out to have Smith-Magenis syndrome, a genomic disorder caused by a deletion on chromosome 17 that is not a metabolic disease at all but which had produced a misleading biochemical signal. One additional case was classified as probable ornithine transcarbamylase deficiency, a urea cycle disorder that can cause lethal hyperammonemia but which often eludes both standard screening and postmortem testing. Among the definitively diagnosed metabolic cases, the spectrum included fatty acid oxidation disorders, which emerged as the dominant category, consistent with the known tendency of these conditions to present as sudden, catastrophic illness in a previously healthy child, sometimes triggered by fasting or infection.

The diagnostic categories named in the study’s abbreviations read like a catalogue of rare but devastating pediatric disease: very-long-chain acyl-CoA dehydrogenase deficiency, carnitine-acylcarnitine translocase deficiency, systemic primary carnitine deficiency, multiple acyl-CoA dehydrogenation deficiency, methylmalonic acidemia, pyruvate dehydrogenase deficiency, ethylmalonic encephalopathy, and mucolipidosis II or III alpha/beta. Each of these conditions has a distinct biochemical signature and a distinct genetic cause, and each is potentially detectable, and in some cases treatable, if identified in time. The fact that they surfaced only after death underscores the central argument of the paper: expanded newborn screening is not universally implemented, and where it is absent or incomplete, lethal metabolic disease can pass through the health system entirely unrecognized.

One of the most clinically informative findings emerged from the comparison between the 13 definitively diagnosed cases and the 37 MS/MS-positive cases that lacked a definitive molecular diagnosis. The diagnosed children had significantly lower rates of low birth weight, 31 percent versus 84 percent; preterm birth, 15 percent versus 78 percent; and obstetric complications, 46 percent versus 78 percent, with P values below 0.001 for the first two comparisons and 0.040 for the third. In other words, the children whose deaths were ultimately explained by inherited metabolic disease were far more likely to have been born at term with normal birth weight and uncomplicated pregnancies. This pattern suggests that a metabolic cause of death should rise higher on the differential diagnosis when a seemingly healthy, full-term baby deteriorates or dies without an alternative explanation, whereas MS/MS abnormalities in preterm or low-birth-weight infants may more often reflect the physiological turbulence of prematurity rather than true inherited disease.

The study also examined how well the biochemical and genetic evidence agreed with each other, a question of real practical importance because discordant findings complicate diagnosis and family counseling. Among the 13 definitively diagnosed cases, clear metabolite-genotype concordance was observed in nine, or 69.2 percent, meaning the biochemical pattern and the pathogenic variants pointed to the same disease. Partial concordance was seen in two cases and non-concordance in two. These discordant cases illustrate a well-known limitation of newborn screening panels: metabolite levels can be influenced by age, feeding, liver function, and prematurity, and a positive screen is not a diagnosis. The authors argue that this is precisely where sequencing adds decisive value, establishing molecular diagnoses and clarifying atypical, nonspecific, or biochemically confusing findings that MS/MS alone cannot resolve.

The implications reach well beyond Shenzhen. The study provides direct evidence that retrospective analysis of archived dried blood spots can convert unexplained pediatric deaths into explained ones, offering families a diagnosis, clarifying recurrence risk for future pregnancies, and identifying relatives who may carry the same condition. Just as importantly, it strengthens the case for broader access to expanded MS/MS newborn screening worldwide, since every undiagnosed case in this cohort represents a child whose condition was, in principle, detectable at birth. The authors advocate a risk-stratified approach to genomic testing, reserving whole-exome sequencing for cases that remain clinically or biochemically unresolved after screening. As sequencing costs continue to fall and blood spot archives grow, the combination of metabolomics and genomics may become a standard tool not only for diagnosing living children but for understanding why some of the most vulnerable never survive their first years.

Subject of Research: Detection of undiagnosed inborn errors of metabolism in unexplained early childhood deaths using newborn dried blood spot screening and whole-exome sequencing

Article Title: Inborn errors of metabolism in unexplained early childhood deaths: a retrospective cohort study combining MS/MS and WES

Article References: Zhou, L., Yang, X., Wu, D., Zhang, L., Tu, X., Zhan, Z., Xie, S., Xu, Y., Liu, C., Wu, B., & Liu, W. (2026). Inborn errors of metabolism in unexplained early childhood deaths: a retrospective cohort study combining MS/MS and WES. BMC Pediatrics. https://doi.org/10.1186/s12887-026-07740-3

Image Credits: AI Generated

DOI: 10.1186/s12887-026-07740-3

Keywords: inborn errors of metabolism, newborn screening, tandem mass spectrometry, whole-exome sequencing, dried blood spots, early childhood mortality, fatty acid oxidation disorders, pediatrics, metabolomics, genetic diagnosis, urea cycle disorders, Shenzhen

The Marseille team, led by Etienne Fortanier and Shahram Attarian, combed through the records of 642 patients tested after their fiftieth birthday at their referral center. Fifty-seven of them, or 8.9 percent, met the study’s strict definition of late-onset CMT: symptoms beginning after age fifty combined with a class 5 pathogenic variant, the highest confidence category in the American College of Medical Genetics and Genomics framework for interpreting sequence variants. That threshold matters. By demanding both a late clinical onset and an unambiguously disease-causing mutation, the investigators filtered out the incidental genetic noise that often complicates interpretation of sequencing results in older populations, where variants of uncertain significance are common.

The clinical picture that emerged was strikingly mild compared with classic early-onset CMT. High arches, known as pes cavus, were present in 80.7 percent of the confirmed cases, and a family history of neuropathy appeared in 63.2 percent. Yet disability remained modest across the group, measured with validated instruments such as the Charcot–Marie–Tooth Neuropathy Score. This mildness is precisely what makes late-onset CMT so easy to miss. A patient who develops slowly progressive numbness and balance trouble at fifty-eight, without dramatic muscle wasting, is far more likely to be worked up for an acquired neuropathy than to be sent for hereditary testing, particularly when the family history is small or incomplete.

The genetic landscape revealed by the sequencing was remarkably diverse. Pathogenic variants were distributed across twenty different genes, a breadth that would have been practically impossible to capture under the old candidate-gene testing paradigm, in which laboratories screened one gene at a time based on the presumed inheritance pattern and nerve conduction profile. The single most common finding was the PMP22 duplication, the canonical cause of the demyelinating CMT1A subtype, present in 32 percent of cases. But a notable share of diagnoses involved genes only recently linked to late-onset phenotypes, including MME, which encodes the membrane metallo-endopeptidase neprilysin, LRSAM1, an E3 ubiquitin ligase involved in autophagy, MPZ, which encodes myelin protein zero, and MFN2, the mitofusin gene that governs mitochondrial fusion.

The prominence of MME and LRSAM1 in this cohort reinforces a growing international consensus that axonal neuropathies beginning in middle and old age carry a distinct genetic signature. Earlier studies from Japan, Italy, France, and the United Kingdom have pointed in the same direction, and whole-genome sequencing efforts have shown that broadening the genetic net raises diagnostic yields substantially. What the Marseille study adds is a decade of single-center consistency: the same referral service, the same testing pipeline, and the same clinical assessment framework applied uniformly across ten years, minimizing the referral and methodological heterogeneity that can distort multi-center surveys.

To understand what distinguishes genuine late-onset CMT from the many other neuropathies that afflict older adults, the researchers assembled a control group twice the size of the case series: 114 age- and sex-matched patients who had negative CMT-targeted sequencing and a confirmed alternative diagnosis. The main alternative diagnoses in this control group were inflammatory neuropathies, including chronic inflammatory demyelinating polyradiculoneuropathy, idiopathic axonal neuropathies, and toxic neuropathies. These are precisely the entities that dominate the differential diagnosis of progressive distal weakness and sensory loss after fifty, and misattributing hereditary disease to one of them carries real consequences, from unnecessary immunoglobulin therapy to missed genetic counseling for adult children who may carry the same variant.

Multivariate analysis distilled the distinction to three independent predictors. A family history of neuropathy, the presence of pes cavus, and a median motor nerve conduction velocity below 38 meters per second were each independently associated with late-onset CMT rather than an acquired alternative. The conduction threshold is technically meaningful: velocities below 38 meters per second in the median nerve conventionally demarcate demyelinating from axonal physiology, and their association with genetically confirmed CMT in this late-onset cohort indicates that even patients whose disease surfaces late often retain the electrophysiological fingerprint of their underlying molecular lesion. In practical terms, a neurologist evaluating an older patient with an unexplained neuropathy now has a compact, bedside-derivable triad that should trigger referral for comprehensive genetic testing.

The implications extend beyond diagnosis into the design of clinical trials. As gene-specific therapies for CMT edge closer to the clinic, natural history data on late-onset populations become essential, because the pace of progression, the burden of disability, and the range of causative genes all differ from the pediatric and young-adult cohorts in which most historical natural history studies were conducted. A trial designed around early-onset CMT1A assumptions may be poorly suited to a sixty-year-old with an MME-related axonal neuropathy that has progressed imperceptibly for a decade. Recognizing that nearly a tenth of tested patients over fifty harbor a genetic diagnosis means trial recruiters, outcome measure developers, and regulatory strategists must account for this older, genetically heterogeneous population.

There are also counseling dimensions that the study only begins to address. Each of the twenty implicated genes carries its own inheritance pattern, penetrance profile, and recurrence risk for offspring. An autosomal dominant MFN2 variant identified in a fifty-four-year-old has immediate implications for siblings and children, some of whom may already be experiencing subtle symptoms they have not connected. Conversely, identifying a recessive MME variant can reassure relatives and reshape reproductive planning. The Marseille findings argue for embedding genetic counselors within neuromuscular clinics that serve older adults, rather than treating hereditary neuropathy as a pediatric subspecialty concern.

The study’s limitations are those inherent to its design. It is retrospective, drawn from a single highly specialized referral center, which likely inflates the proportion of genetically confirmed cases relative to community practice, where testing rates remain low and referral thresholds high. The 8.9 percent figure should therefore be read as a prevalence among tested patients, not among all older adults with neuropathy. Still, the message travels well beyond Marseille: in the next-generation sequencing era, the age cutoffs that once guided who deserved hereditary testing have lost their justification. A family history, high arches, and slowed median nerve conduction in a patient of any age should now be enough to open the door to a comprehensive gene panel, because the genetic causes of neuropathy clearly do not respect a fiftieth birthday.

Subject of Research: Genetically confirmed late-onset Charcot–Marie–Tooth neuropathy diagnosed by next-generation sequencing in patients over 50

Article Title: Late-onset CMT neuropathy in the NGS era: a 10-year retrospective study

Article References: Fortanier, E., Bonello-Palot, N., Verschueren, A., Kouton, L., Grapperon, A.-M., Salort-Campana, E., Corazza, G., de Bovis, V. M., du Closel, L. B., Delmont, E., & Attarian, S. (2026). Late-onset CMT neuropathy in the NGS era: a 10-year retrospective study. Journal of Neurology, 273(10), Article 624. https://doi.org/10.1007/s00415-026-14154-9

Image Credits: AI Generated

DOI: 10.1007/s00415-026-14154-9

Keywords: Charcot-Marie-Tooth disease, hereditary neuropathy, next-generation sequencing, late-onset disease, PMP22 duplication, MME, LRSAM1, MPZ, MFN2, pes cavus, nerve conduction velocity, genetic diagnosis

Prader-Willi syndrome arises from errors in the expression of paternally inherited genes on chromosome 15, affecting roughly one in ten thousand to one in thirty thousand births. Infants with the condition typically show weak muscle tone, a poor suck that makes feeding difficult, and mild facial differences such as a narrow forehead, almond-shaped eyes, and a downturned mouth. As childhood progresses, the picture changes dramatically: an unrelenting drive to eat emerges, leading to life-threatening obesity if not managed, alongside cognitive and behavioral difficulties. Early recognition matters enormously, because growth hormone therapy, feeding support, and structured developmental care initiated soon after birth can measurably improve outcomes. The catch is that the neonatal facial phenotype, the very signal clinicians might rely on, is faint and easily overlooked in a squirming, sleeping infant.

The Fudan team, led by Yunqian Zhu and Wenhao Zhou, set out to build a diagnostic aid that works precisely where existing tools falter. Their strategy rested on a pragmatic observation: photographs of older children with the syndrome are relatively abundant, while images of newborns are scarce and expensive to collect. Could a model trained on the faces of older children still detect the syndrome in newborns whose facial features are far less pronounced? To find out, the researchers assembled a training cohort of 113 children drawn from a public platform, of whom 21 carried confirmed diagnoses of Prader-Willi syndrome, and a separate validation cohort of newborns at their own hospital consisting of ten affected infants and thirteen controls.

The technical approach combined multiple feature sets and learning algorithms. The team extracted a detailed panel of facial measurements, including distances, angles, and shape descriptors capturing everything from eye spacing to lip contour, alongside age. They then trained six different classification algorithms, spanning from logistic regression to Random Forests and AdaBoost ensembles, on three versions of the feature set: the complete panel, a top-ten subset of the most informative features, and a clinically selected subset chosen for relevance to the syndrome. Performance was judged using the area under the precision-recall curve, a metric well suited to datasets where positive cases, like rare diseases, are outnumbered by controls. Across all feature sets, the Random Forest and AdaBoost models emerged as the strongest performers.

The headline result came from the Random Forest trained on the complete feature set. In cross-validated testing on the training cohort, it achieved a mean sensitivity of 0.97, with a 95 percent confidence interval stretching from 0.84 to 1.00, and a specificity of 0.95, correctly identifying nearly every child with the syndrome while rejecting nearly all children without it. The model was also well calibrated, meaning its predicted probabilities tracked actual likelihoods rather than being systematically overconfident or timid, a property the researchers emphasize as essential for any tool intended to support real clinical decisions rather than inflate benchmark scores.

Peering inside the model revealed a face in numbers. Age, face width, and features of the upper lip carried the greatest predictive weight, consistent with the well-described dysmorphic profile of the syndrome. More intriguingly, the analysis surfaced four facial features not previously reported in the context of Prader-Willi syndrome: jaw symmetry, chin shape, nose width, and jaw width. A sensitivity analysis showed that 26 facial features contributed more to classification than age alone, suggesting that the model was genuinely reading facial structure rather than simply learning that children with the condition tend to be photographed at certain ages. These newly identified dimensions of the syndrome’s facial signature could inform clinicians and researchers alike, expanding what is understood about how a single genetic lesion reshapes craniofacial development.

The decisive test, however, was neonatal. When the researchers applied their child-trained model to the newborn validation cohort, they first had to adjust the decision threshold, because the probability scores that fit older children needed recalibration for the subtler neonatal face. After this re-estimation, the Random Forest model detected 80 percent of affected newborns while correctly clearing 77 percent of controls. To benchmark this performance, the team compared it against Face2Gene, a widely used commercial facial analysis app for genetic syndromes. On the same newborn images, Face2Gene achieved only 70 percent sensitivity and a mere 15 percent specificity, meaning it flagged almost every baby as suspect. At a false positive rate of 0.25 or less, the Fudan model delivered comparable sensitivity but dramatically higher specificity, a distinction that matters in a screening context where alarmingly frequent false alarms would erode trust and swamp follow-up genetic testing capacity.

Beyond the immediate clinical promise, the study carries a broader methodological message for the field of computational phenotyping. Artificial intelligence tools for rare disease detection, including deep learning systems such as DeepGestalt and GestaltMatcher, have demonstrated impressive diagnostic power in clinics and genetic consultation settings, but their training data overwhelmingly feature older children and adults. Newborns, with their rounded faces, abundant subcutaneous fat, and physiologically underdeveloped craniofacial structures, represent a distribution shift that most models handle poorly. The Fudan results suggest a practical workaround: rather than waiting years to accrue a newborn dataset of sufficient size, researchers can train on pediatric data and transfer the learned phenotype knowledge to neonates through careful threshold adjustment. That could accelerate screening tools for a whole family of genetic conditions where the newborn window of intervention is narrow and the data pipeline begins nearly empty.

Caveats remain, and the authors are candid about them. The validation cohort numbered just 23 newborns, a pilot sample sufficient to demonstrate feasibility but far short of what a population-level screening program would demand. The control group’s size and composition limit how confidently the specificity estimates can be generalized, and the model must eventually prove itself across diverse ethnic populations, camera conditions, and gestational ages. The researchers also note that facial analysis is intended as a triage tool, not a replacement for the methylation testing that definitively diagnoses the syndrome. A positive screen would simply channel scarce genetic testing resources toward the babies most likely to benefit, shortening what can otherwise be a diagnostic odyssey measured in months or years.

Still, the trajectory of the work is hard to ignore. With a new drug recently approved to treat hyperphagia in older patients and advances such as hypothalamic organoids offering laboratory models of the underlying biology, the therapeutic landscape for Prader-Willi syndrome is shifting, and the value of catching the condition at birth rises in step. A camera and an algorithm cannot replace a pediatric geneticist, but they can stand watch over every delivery ward, quietly and cheaply, flagging the one baby in ten thousand whose face holds a message that human eyes, on their own, too often miss. If larger prospective studies replicate the Shanghai results, facial phenotype screening could become the first step of a standard newborn pathway, ensuring that children with Prader-Willi syndrome receive growth hormone, feeding support, and early intervention before the syndrome’s most damaging consequences take root.

Subject of Research: Machine learning-based facial phenotype screening for early detection of Prader-Willi syndrome in newborns

Article Title: Early identification of Prader-Willi syndrome in newborns using facial phenotype-based machine learning

Article References: Zhu, Y., Chen, H., Chen, J., Yang, L., Dong, X., Ni, Q., & Zhou, W. (2026). Early identification of Prader-Willi syndrome in newborns using facial phenotype-based machine learning. Pediatric Research. https://doi.org/10.1038/s41390-026-05491-6

Image Credits: AI Generated

DOI: 10.1038/s41390-026-05491-6

Keywords: Prader-Willi syndrome, machine learning, facial phenotype, newborn screening, rare disease, random forest, Face2Gene, genetic diagnosis, dysmorphism, pediatric research, artificial intelligence, early diagnosis

X-linked sideroblastic anemia, or XLSA, arises from pathogenic variants in ALAS2, a gene carried on the X chromosome that provides the blueprint for erythroid-specific 5-aminolevulinate synthase, the first and rate-limiting enzyme in heme biosynthesis. When the enzyme falters, developing red blood cells cannot manufacture heme efficiently, and iron piles up inside their mitochondria instead of being incorporated into hemoglobin. Under the microscope, these iron-laden mitochondria ring the nucleus of immature erythroid cells, producing the ring sideroblasts that give the disease its name. Because the gene sits on the X chromosome, the condition typically follows an X-linked recessive pattern: hemizygous males, who possess only one X chromosome, are usually the ones who fall ill, while heterozygous females often remain asymptomatic or show only mild anemia thanks to their second, healthy copy.

The girl in this report had been flagged during a routine physical examination eight years before referral, when she was initially diagnosed with iron-deficiency anemia. Oral iron supplements failed to lift her hemoglobin, and two years before admission she began complaining of dizziness and fatigue. Testing at that point revealed macrocytic anemia accompanied by folate deficiency, and a bone marrow aspiration showed mild dyserythropoiesis, prompting a diagnosis of nutritional anemia. She was treated with high-dose oral folic acid, later combined with mecobalamin, a form of vitamin B12. The anemia proved stubbornly refractory: hemoglobin hovered around 80 g/L and then slid to roughly 60 g/L after another year of therapy, at which point she was referred for specialist evaluation.

On admission, her hemoglobin measured 59 g/L, with red cell indices pointing firmly toward macrocytosis: a mean corpuscular volume of 113.1 fL, well above the normal range, and a mean corpuscular hemoglobin of 36.9 pg. Reticulocyte analysis told an equally important story. Although the reticulocyte percentage was mildly elevated at 2.48 percent, the calculated reticulocyte production index, adjusted for her severe anemia, came out at approximately 0.40, a value far too low for the degree of anemia. That discrepancy signaled ineffective erythropoiesis: the bone marrow was working hard but producing few usable red cells. White blood cell and platelet counts, crucially, remained normal, arguing against a broad marrow failure syndrome.

Iron studies then delivered a decisive clue. Serum ferritin was markedly elevated at 871.7 micrograms per liter, and serum iron reached 44.12 micromoles per liter, with an unsaturated iron-binding capacity below the detectable limit, together painting a picture of substantial iron overload rather than iron deficiency. Nutritional markers showed borderline folate at 4.14 nanograms per milliliter, interpreted as persistent functional folate deficiency given her continuous supplementation, and a normal vitamin B12 level. Hemolysis markers added further complexity: plasma free hemoglobin was elevated, haptoglobin was nearly abolished, and both indirect and total bilirubin were raised, consistent with hemolytic activity or ineffective erythropoiesis. Erythropoietin, the kidney hormone that drives red cell production, was dramatically elevated at 213.62 mIU/mL, reflecting the marrow’s desperate attempt to compensate. A Coombs test was negative, ruling out autoimmune hemolysis, and the osmotic fragility test was unremarkable.

Morphology told its own story. The peripheral blood smear displayed striking anisocytosis and poikilocytosis, with red cells of wildly varying size and shape, including ovalocytes and teardrop cells. Bone marrow aspiration revealed relative erythroid hyperplasia dominated by intermediate and late erythroblasts, and the biopsy was markedly hypercellular at over 90 percent with erythroid predominance. Flow cytometry found no increase in myeloblasts and no monoclonal lymphoid population, helping exclude a clonal marrow cancer. Globin gene sequencing came back clean, ruling out thalassemia and related hemoglobin disorders, leaving the underlying cause still shrouded.

The breakthrough came from whole exome sequencing of bone marrow mononuclear cells, which uncovered a frameshift insertion in ALAS2: c.1277dupT, resulting in the protein change p.M426Ifs*66. Sanger sequencing confirmed the variant. A frameshift of this kind is catastrophic for protein architecture: the reading frame collapses, and the resulting truncated protein loses critical C-terminal functional domains. Structural modeling with AlphaFold 3 suggested the truncation disrupts the three-dimensional conformation of the enzyme’s active site, specifically displacing the Lys391 residue, the catalytic lysine that forms the essential Schiff base linkage with the pyridoxal 5′-phosphate cofactor. Without that interaction, the enzyme is predicted to be catalytically inert. The variant was therefore classified as highly pathogenic, providing molecular confirmation of XLSA. Notably, the sequencing also surfaced two missense variants in DHX34, predicted deleterious and potentially linked to familial myelodysplastic syndrome or acute myeloid leukemia risk, plus variants in FANCI and BRIP1 classified as uncertain in significance; without segregation or functional data, the team could not assign any of them a causal or modifying role in her blood disorder.

The diagnostic journey required careful exclusion of look-alike conditions. Myelodysplastic neoplasm with SF3B1 mutation, the commonest acquired cause of ring sideroblasts, was considered unlikely given the childhood onset, isolated anemia with preserved white cells and platelets, absence of excess myeloblasts, and the germline ALAS2 finding, though bone marrow iron staining was never performed, so ring sideroblasts could not be formally assessed. Congenital dyserythropoietic anemia, with its characteristic multinucleated erythroblasts and chromatin bridges, found no morphological support, and the features of Pearson syndrome, Diamond-Blackfan anemia, GATA1-related disorders, and telomere biology disorders were all absent. After the molecular diagnosis, the patient continued transfusions as needed for symptomatic anemia, with ferritin monitored but iron chelation not yet started. At last contact she remained transfusion-dependent and subsequently did not return for follow-up, leaving her long-term course unknown.

The case carries broader lessons for hematology. More than 100 pathogenic ALAS2 variants have now been described, scattered across nearly every exon with no clear mutational hotspots, and missense mutations account for roughly 90 percent of cases, making this frameshift a rare and severe class of defect. The authors propose that such profound loss of function may explain the unusually early onset in this female patient. Why she was macrocytic rather than microcytic remains the most intriguing question. Prior work suggests that in symptomatic heterozygous females, skewed X-chromosome inactivation leaves the mutant allele active in erythroid cells, and that circulating red cells derive almost exclusively from wild-type lineages, because ALAS2-deficient clones cannot complete terminal differentiation. Under hypoxic stress and soaring erythropoietin, those surviving wild-type cells may mature prematurely, dividing fewer times and emerging larger, a model the authors frame as hypothetical since X-inactivation studies could not be performed. The family declined further genetic testing, iron staining of stored marrow was never authorized, and transfusion began before pyridoxine response could be tested, though a complete loss-of-function variant was unlikely to respond to the vitamin B6 cofactor anyway. Clinically, the message is clear: when macrocytic anemia resists folate and B12, especially alongside iron overload and a poor reticulocyte response, inherited sideroblastic anemia deserves a place on the differential, and genomic sequencing can end years of diagnostic limbo.

Subject of Research: A novel ALAS2 frameshift mutation causing severe macrocytic X-linked sideroblastic anemia in a female patient

Article Title: Severe Macrocytic Anemia Associated With a Novel ALAS2 Mutation: A Case Report and Literature Review

Article References: Cai, H., Shen, K., Wang, J., Gu, J., Zhang, M., & Xiao, M. (2026). Severe Macrocytic Anemia Associated With a Novel ALAS2 Mutation: A Case Report and Literature Review. Clinical Case Reports, 14(9), Article e73529. https://doi.org/10.1002/ccr3.73529

Image Credits: AI Generated

DOI: 10.1002/ccr3.73529

Keywords: ALAS2, X-linked sideroblastic anemia, macrocytic anemia, heme biosynthesis, ring sideroblasts, whole exome sequencing, iron overload, frameshift mutation, X-chromosome inactivation, ineffective erythropoiesis, refractory anemia, genetic diagnosis

The story begins when a previously healthy five-year-old girl was referred to the neurology unit with a fixed right mydriasis, a persistently dilated pupil, and complete retinal detachment in the same eye. Notably, she had never experienced fever or eye pain, features that might otherwise have steered clinicians toward an infectious or inflammatory process of a different character. Brain magnetic resonance imaging revealed severe right optic neuritis, appearing as hyperintensity on T2-weighted sequences, and serum testing detected anti-MOG antibodies at a low titer of 1:10. On the strength of these findings, the team diagnosed MOGAD, an autoimmune condition in which antibodies target myelin oligodendrocyte glycoprotein, a protein on the surface of myelin sheaths in the central nervous system, and initiated monthly intravenous immunoglobulin at a dose of 2 grams per kilogram.

The initial treatment did not hold the disease in check. Three months later, the girl suffered a brainstem relapse marked by vomiting, dysarthria, and ataxia. Repeat MRI showed contrast-enhancing lesions in both supra- and infratentorial regions, together with tonsillar herniation and obstructive hydrocephalus, a life-threatening buildup of cerebrospinal fluid pressure that required a third ventriculocisternostomy, a surgical bypass procedure. High-dose intravenous methylprednisolone pulses of 20 milligrams per kilogram per day were administered for seven days and produced only partial improvement. Despite ongoing therapy, a further relapse followed just three months later, this time presenting with cerebellar ataxia, dysarthria, and a right foot drop. The clinical picture was that of a refractory, relentlessly relapsing inflammatory disorder of the central nervous system, and the team escalated accordingly.

Faced with this refractory-relapsing MOGAD phenotype, the clinicians turned to rituximab, a monoclonal antibody that depletes CD20-positive B cells and is increasingly used as second-line therapy in antibody-mediated neuroinflammatory disease. The drug was given at 375 milligrams per square meter of body surface area weekly for four weeks, but it was discontinued after yet another relapse. Mycophenolate mofetil at 1000 milligrams per day was then added to the monthly immunoglobulin cycles, and this combination finally produced a more stable remission lasting three years. Even during this quiescent period, however, a subtle clue persisted: the girl’s anti-MOG antibody titers fluctuated, swinging between positive and negative results. The authors emphasize precisely this point in their critique, arguing that the role of MOG-IgG serum titer changes and oscillations should not be solely used to clarify the nature of neuroinflammatory pictures in children.

The remission shattered when the girl was 9.6 years old. She abruptly developed a crossed brainstem syndrome, a pattern of neurological deficits produced by a lesion interrupting nerve tracts and cranial nerve nuclei within the brainstem, manifesting as right lower limb hypertonia, flaccid paralysis of the left arm, anarthria, or complete loss of speech, lingual akinesia, and a fixed rightward deviation of the head. A new brain MRI revealed multiple hemorrhagic lesions lined through the thalamus, the nucleo-capsular regions, and the pons. Hemorrhagic transformation within inflammatory brain lesions of this severity is distinctly unusual for typical MOGAD and signaled that the underlying process was something far more destructive than a conventional demyelinating disease.

At this critical juncture, the clinicians returned to a physical sign that had been present all along: the girl’s silvery-gray hair and eyebrows. This peculiar pigmentation, easily overlooked or attributed to benign variation in a child with an autoimmune diagnosis, is in fact the hallmark of Griscelli syndrome, a group of autosomal recessive disorders defined by partial albinism. Acting on this reassessment, the team performed a molecular testing panel for hemophagocytic lymphohistiocytosis, or HLH, a hyperinflammatory syndrome in which immune cells attack the body’s own tissues and organs, using peripheral blood mononuclear cells. The panel revealed two variants in the RAB27A gene on chromosome 15q21: c.153+5G>A, a splice site variant that alters pre-mRNA splicing, and c.514_518del, a pathogenic five-base-pair deletion.

The molecular findings confirmed Griscelli syndrome type 2, catalogued as OMIM #607623, an ultrarare condition caused by mutations in RAB27A and characterized by partial albinism together with impaired cytotoxic activity of T cells and natural killer cells, carrying a risk of life-threatening hemophagocytic lymphohistiocytosis. The biology connects the two seemingly unrelated features of the case. The Rab27a protein is essential for the release of melanin from melanocytes into surrounding cells; when it is dysfunctional, melanin accumulates abnormally within melanocytes and is not transferred properly, producing the characteristic silvery-gray hair and skin hypopigmentation. The same protein is required for the release of cytolytic granules by cytotoxic lymphocytes, so its absence leaves the immune system unable to eliminate infected or activated cells, permitting uncontrolled immune activation that can culminate in the cytokine storm of HLH.

Importantly, the authors note that HLH may be virtually absent in some patients who present with a completely neurologic phenotype, even when molecular findings are fully consistent with Griscelli syndrome type 2. This phenotypic expansion, previously described in the literature in an eleven-year-old girl with Rab27A mutations and no hemophagocytosis, helps explain why the diagnosis remained hidden for more than five years in the present case. After the genetic confirmation, the girl was started on ruxolitinib, a Janus kinase inhibitor that dampens inflammatory signaling downstream of cytokine receptors, at a dose of 5 milligrams twice daily, and she was placed on the waiting list for hematopoietic stem cell transplantation, the only curative option for this disease. Sadly, a slowly progressive multiorgan failure developed five months later, and the girl died at the age of ten.

The case carries a pointed lesson for pediatric neurologists and immunologists alike. Rare genetic errors of immunity can coexist with hypopigmentation skin disorders, and the authors urge healthcare providers to recall that dysregulated immunity may be camouflaged by devastating neuroinflammatory pictures that begin with something as common as optic neuritis. Autoimmune test results, including anti-MOG positivity, may taint the true disease identity, because a positive MOG test does not automatically mean MOGAD. Low antibody titers, atypical clinical features such as absent pain, hemorrhagic lesions, relapses refractory to appropriately escalated immunotherapy, and fluctuating serology should all prompt a broader differential diagnosis that includes inborn errors of immunity. In such patients, recognizing subtle dysmorphic or pigmentation cues and pursuing molecular panels early can redirect treatment toward targeted immunomodulation and, ultimately, curative transplantation before irreversible damage accumulates.

Published as a letter in response to Aduru and colleagues’ finding that MOGAD is the most common cause of isolated optic neuritis in children, this report does not overturn that conclusion but complicates it. It stands as a reminder that the most frequent explanation is not always the correct one, and that in medicine, as in this child’s silver-gray hair, the most visible clue to a hidden diagnosis may be the one easiest to dismiss.

Subject of Research: Griscelli syndrome type 2 masquerading as MOG antibody-associated neuroinflammatory disease in a child

Article Title: A Lethal Progressive Neuroinflammation Disguised as MOGAD Revealing a Final Diagnosis of Griscelli Syndrome

Article References: Veredice, C., Arpaia, C., Contaldo, I., Capasso, A., & Rigante, D. (2026). A Lethal Progressive Neuroinflammation Disguised as MOGAD Revealing a Final Diagnosis of Griscelli Syndrome. Annals of Clinical and Translational Neurology, 13(8), 1740-1742. https://doi.org/10.1002/acn3.70470

Image Credits: AI Generated

DOI: 10.1002/acn3.70470

Keywords: Griscelli syndrome, MOGAD, optic neuritis, RAB27A, hemophagocytic lymphohistiocytosis, neuroinflammation, pediatric neurology, anti-MOG antibodies, partial albinism, rituximab, ruxolitinob, genetic diagnosis