Thrombotic microangiopathy, or TMA, is classically taught as a triad: microangiopathic hemolytic anemia, in which red blood cells are shredded as they squeeze through partially occluded vessels; thrombocytopenia, a dangerous drop in platelets consumed by runaway clotting; and ischemic damage to end organs, most often the kidneys. But medicine’s tidy categories are increasingly breaking down. A growing body of evidence shows that many patients never develop the dramatic hematologic signature at all. Instead, they present with nothing more than a quietly rising serum creatinine, the standard marker of kidney dysfunction. When kidney biopsy confirms the characteristic vascular pathology in these patients, the entity is called renal-limited TMA, or RL-TMA. A French retrospective study cited by the case authors found that this localized form may account for as many as 45 percent of TMA cases, yet its indolent course and non-specific presentation mean it is frequently overlooked.

The patient at the center of this report arrived at the gastroenterology department with intermittent melena, the passage of digested blood that signals upper gastrointestinal bleeding. His blood pressure measured a staggering 218 over 140 millimeters of mercury despite a five-year history of hypertension for which he had never taken a single antihypertensive medication, a family pattern echoed by his father and grandfather, both diagnosed in their thirties. His serum creatinine was severely elevated at 437 micromoles per liter, indicating acute kidney injury on a background of chronic damage. Yet his initial laboratory profile was strikingly atypical for TMA: platelets were actually high at 578 billion per liter, no schistocytes, the fragmented red cells that hallmark microangiopathic hemolysis, were seen on his blood smear, and lactate dehydrogenase and bilirubin were normal. The absence of systemic hematologic involvement would prove to be the first clue that this was a disease confined almost entirely to the kidney.

The differential diagnosis was daunting. Uncontrolled hypertension with renal impairment, anemia, and a suspicious monoclonal protein band on serum electrophoresis raised immediate concern for multiple myeloma and monoclonal gammopathy of renal significance, known as MGRS. Immunofixation electrophoresis revealed an IgA-kappa monoclonal immunoglobulin, and the serum free light chain assay showed an abnormal involved-to-uninvolved ratio of 2.73, though still within the renal-function-corrected reference limit of 3.1. Bone marrow aspiration, however, showed normocellular marrow with no clonal plasma cell proliferation. After intensive antihypertensive therapy brought his blood pressure to roughly 150 over 90 and produced partial renal recovery, the clinical team finally persuaded the reluctant patient to undergo kidney biopsy on day 45 after symptom onset, a delay that would later carry therapeutic consequences.

The biopsy findings were textbook for TMA confined to the renal microvasculature. Of twelve glomeruli examined, three were globally sclerosed, and the surviving filters showed ischemic collapse of capillary tufts with a small fibrous crescent. The arterioles told the deeper story: walls thickened with mucinous degeneration, the so-called onion-skin intimal hyperplasia characteristic of malignant hypertensive vascular injury, severe luminal stenosis, and visible thrombus formation. Roughly 80 percent of tubules were atrophied amid diffuse interstitial fibrosis, evidence of irreversible chronic damage. Direct immunofluorescence showed no immunoglobulin or complement deposits, and even immunoelectron microscopy found no clear monoclonal light chain deposition, meaning the paraprotein had left no direct histologic fingerprint on the kidney.

Then came the complement workup, and with it the case’s central paradox. Soluble membrane attack complex, sC5b-9, the terminal effector of the complement cascade whose elevation signals ongoing activation of the pathway that eculizumab is designed to block, was massively elevated at greater than 2100 nanograms per milliliter against a normal range of 75 to 219. There were no antibodies against complement factors H, B, or I, ADAMTS13 activity was normal, ruling out thrombotic thrombocytopenic purpura, stool culture was negative, excluding Shiga toxin-producing Escherichia coli-associated HUS, and whole-exome sequencing found no pathogenic variants in complement pathway genes. The picture pointed to complement-mediated TMA driven by malignant hypertension, with the monoclonal gammopathy as a probable co-conspirator rather than a proven direct injurer.

After intensifying antihypertensive therapy with sacubitril/valsartan, the team initiated eculizumab, the recombinant humanized monoclonal antibody against complement component C5 that prevents formation of the membrane attack complex. The regimen followed the standard aHUS protocol: 900 milligrams weekly for four weeks, then 1200 milligrams every two weeks. For the first month, things looked promising. Serum creatinine fell from 277 to 248 micromoles per liter. But by week 10, it had rebounded to 335. Here is the technical crux: throughout treatment, CH50, the 50 percent hemolytic complement assay, sat at 13.7 to 13.8 units per milliliter against a reference range of 23.0 to 46.0, and sC5b-9 had dropped to 280 to 335 nanograms per milliliter, near-normal territory. The terminal complement pathway was completely and sustainably inhibited. The drug was doing exactly what it is supposed to do. The kidney was deteriorating anyway.

This disconnect between pharmacologic success and clinical failure is where the case becomes genuinely instructive. The authors attribute the suboptimal response to two converging factors. First, delayed initiation: evidence suggests eculizumab should ideally be started within 24 to 48 hours of disease onset, yet the diagnostic difficulty of RL-TMA, which typically requires renal biopsy for confirmation in the absence of specific biomarkers, meant complement blockade began 45 days after symptoms appeared. By then, the biopsy had already documented approximately 80 percent tubular atrophy with diffuse interstitial fibrosis, structural changes that no amount of complement inhibition can reverse. Second, complement-independent mechanisms: the persistent IgA-kappa paraprotein, though never demonstrated as direct renal deposition, may have sustained endothelial damage through indirect pathways. Mayo Clinic data analyzed by Ravindran and colleagues found that 13.7 percent of 146 TMA patients had paraproteinemia, roughly four times more common than expected, positioning monoclonal immunoglobulin as a potential susceptibility factor for the second hit that tips endothelial injury into full-blown microvascular thrombosis.

With the patient’s consent, the team pivoted the day after discontinuing eculizumab to empirical plasma cell-directed therapy: weekly bortezomib at 2.6 milligrams per square meter, cyclophosphamide 600 milligrams, and dexamethasone 20 milligrams. The response was gradual but sustained. By week 7 of anti-myeloma therapy, creatinine had declined to 261 micromoles per liter. At the day-300 follow-up visit, it stood at 233, with the monoclonal protein persisting at low concentration, involved free light chain of 36.82 milligrams per liter and a ratio of 1.91. The concurrent improvement in renal function and decline in paraprotein levels provides compelling clinical evidence that the monoclonal immunoglobulin was a genuine pathogenic driver of this complex TMA phenotype, even without histologic proof of direct deposition.

The broader literature on eculizumab in RL-TMA is vanishingly small. A PubMed search combining the terms thrombotic microangiopathy and renal-limited yields only 22 references, including six reviews, and just four publications covering a total of 11 cases specifically address eculizumab treatment. Among those 11 patients, only two responded effectively with renal function recovery and dialysis discontinuation, while five showed no improvement and progressed to end-stage renal disease. The pattern suggests eculizumab demonstrates inferior efficacy in RL-TMA compared to systemic TMA, a finding this case, with its dual malignant hypertension and monoclonal gammopathy etiology, reinforces. The take-home messages are twofold: patients with TMA should be routinely screened for underlying monoclonal immunoglobulinemia, and C5 inhibitor therapy should be initiated as promptly as possible, because in a disease whose diagnosis is confirmed only by biopsy, every day of delay allows irreversible structural damage to accumulate beyond the reach of even the most complete complement blockade.

Subject of Research: Suboptimal Response to Eculizumab in Renal‐Limited Thrombotic Microangiopathy Associated With Malignant Hypertension and Monoclonal Gammopathy: A Case Report

Article Title: Suboptimal Response to Eculizumab in Renal‐Limited Thrombotic Microangiopathy Associated With Malignant Hypertension and Monoclonal Gammopathy: A Case Report

Article References: Lei, W., Shi, T., Xu, M., & Zhou, J. (2026). Suboptimal Response to Eculizumab in Renal‐Limited Thrombotic Microangiopathy Associated With Malignant Hypertension and Monoclonal Gammopathy: A Case Report. Clinical Case Reports, 14(10), Article e73712. https://doi.org/10.1002/ccr3.73712

Image Credits: AI Generated

DOI: 10.1002/ccr3.73712

Keywords: thrombotic microangiopathy, eculizumab, complement, malignant hypertension, monoclonal gammopathy, kidney disease, renal-limited TMA, bortezomib, MGRS, case report, Suboptimal, Response

The proband, a woman in her late forties, had endured recurrent episodes of non-pitting edema affecting her face, extremities, and abdomen since her mid-teens. The attacks, estimated at fifteen to twenty per year, each lasted two to four days, occurred without the hives that characterize allergic swelling, and stubbornly resisted antihistamines, glucocorticoids, and even epinephrine. She had never taken the medications most often implicated in drug-induced angioedema, including angiotensin-converting enzyme inhibitors, angiotensin-receptor blockers, dipeptidyl peptidase-4 inhibitors, or exogenous estrogens. Crucially, she also carried a diagnosis of systemic lupus erythematosus made in adolescence, though the disease had remained clinically quiescent on stable low-dose prednisolone, with no recent flares, significant proteinuria, serositis, or active mucocutaneous disease.

Laboratory testing performed in both 2020 and 2022 painted a picture that seemed, at first glance, unambiguous. Her C4 levels sat persistently at 3.0 milligrams per deciliter, far below normal. Her C1-inhibitor antigen levels measured 7 and then 5 milligrams per deciliter, with functional activity of 31 percent and then less than 25 percent — a pattern classic for type 1 C1-inhibitor deficiency, in which the protein is both quantitatively reduced and functionally impaired. But then came the anomaly: C1q was undetectable at both time points, falling below the assay’s detection limit of 1.5 milligrams per deciliter on each occasion.

That finding should have pointed decisively toward acquired angioedema. In the hereditary form of the disease, C1q is typically normal, because the genetic defect impairs only the C1-inhibitor protein itself, leaving the rest of the classical complement pathway largely intact. In the acquired form, by contrast, consumption or autoimmune destruction of C1-inhibitor triggers runaway activation of the classical pathway, dragging C1q down with it. Profoundly low C1q has therefore long been regarded as one of the most reliable biochemical fingerprints separating the two conditions. Faced with an undetectable C1q in a middle-aged woman, the clinical team reasonably worried that an acquired process — potentially signaling an underlying lymphoproliferative disorder or monoclonal gammopathy — was hiding beneath the surface.

The initial workup, however, came back clean. Serum protein electrophoresis with immunofixation revealed no monoclonal protein, and computed tomography showed no lymphadenopathy. Anti-C1q antibodies, anti-C1-inhibitor antibodies, and sequencing of the SERPING1 gene — the gene whose mutations cause hereditary angioedema type 1 and type 2 — had not yet been performed at the time of publication, and the authors are careful to acknowledge that they cannot claim definitive exclusion of acquired disease. What they could do, and what ultimately proved decisive, was something far simpler and more powerful: test the family.

Five biologically related individuals spanning three generations, including members of a collateral line, underwent repeat complement testing. The results were striking in their internal consistency. The proband’s son, sister, niece, and father all showed reproducibly low C4 alongside low C1-inhibitor antigen and function — the biochemical signature of type 1 hereditary angioedema — yet none of them had lupus. And their C1q values told a completely different story from the proband’s. The son’s C1q measured 14.7 and then 13.8 milligrams per deciliter; the sister’s, 10.1 and then 11.0; the niece’s, 12.4 and then 10.7 — all comfortably within reference ranges. Only the father showed subnormal C1q at 6.9 and then 6.1 milligrams per deciliter, but his position within a multigenerational pedigree carrying the same C1-inhibitor defect still argued strongly for hereditary transmission rather than an independent acquired process.

The overall pattern, the authors conclude, was not acquired angioedema with low C1q, but familial C1-inhibitor deficiency with discordant C1q values — with the most extreme reduction confined to the one family member who also had systemic lupus erythematosus. This distinction is far from academic. Hereditary angioedema and lupus have been reported together before, and their coexistence can complicate complement interpretation in ways that clinicians may not anticipate. Low serum C1q can arise from multiple distinct mechanisms: inherited C1q deficiency, immune-complex-mediated consumption of the classical pathway as seen in active lupus, hypocomplementemic urticarial vasculitis, or cryoglobulinemic vasculitis, and acquired C1-inhibitor deficiency associated with monoclonal gammopathy, lymphoproliferative disease, or autoimmunity. In this patient, the absence of severe childhood infections, urticarial vasculitis-like lesions, cryoglobulinemic features, monoclonal protein, or lymphadenopathy made most alternatives unlikely, leaving overlapping lupus as the most plausible driver of her extreme C1q reduction.

The clinical stakes of getting this right are considerable. Labeling the proband as having acquired angioedema on the basis of C1q alone would have contradicted her adolescent onset, a clear three-generation familial pattern, and repeated concordant deficiency of C1-inhibitor antigen and function in her relatives. It would also have redirected her clinical care toward surveillance for hematologic malignancy rather than management of a lifelong genetic condition with well-established treatment pathways. Conversely, the authors emphasize, a low C1q result should never simply be ignored. It justifies structured surveillance and confirmatory testing, particularly because acquired C1-inhibitor deficiency can be associated with monoclonal gammopathy and hematologic disease that require their own monitoring and intervention.

The report also extends an earlier family description published by the same group, adding two new dimensions: serial C1q measurements across all tested relatives, and direct demonstration that profound C1q reduction can coexist with hereditary C1-inhibitor deficiency in a patient with overlapping lupus. The principal limitation remains the absence of molecular and autoantibody confirmation — SERPING1 sequencing and anti-C1-inhibitor antibody testing are still pending. Even so, the most parsimonious interpretation, the authors argue, is hereditary type 1 C1-inhibitor deficiency with lupus-associated or immune-mediated C1q reduction in the proband, rather than acquired angioedema diagnosed on the strength of a single complement value.

The broader lesson for clinicians managing recurrent angioedema is one of disciplined humility toward individual biomarkers. In patients with recurrent swelling — especially when onset is early and family clustering is evident — very low C1q should trigger a thorough confirmatory evaluation for acquired disease, but it should never be allowed to override a hereditary pattern revealed by age at onset, family history, and repeated testing of relatives. Complement biology, like the patients it serves, rarely obeys a single number.

Subject of Research: Diagnostic pitfalls of low C1q in distinguishing hereditary from acquired C1-inhibitor deficiency angioedema in a family with overlapping systemic lupus erythematosus

Article Title: Low C1q alone should not be taken as diagnostic of acquired angioedema in a kindred with familial type 1 C1-inhibitor deficiency and overlapping systemic lupus erythematosus

Article References: Takagi, A., Takamura, S., & Fukuda, T. (2026). Low C1q alone should not be taken as diagnostic of acquired angioedema in a kindred with familial type 1 C1-inhibitor deficiency and overlapping systemic lupus erythematosus. Journal of Cutaneous Immunology and Allergy, 9, Article 16999. https://doi.org/10.3389/jcia.2026.16999

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DOI: 10.3389/jcia.2026.16999

Keywords: hereditary angioedema, acquired angioedema, C1-inhibitor deficiency, C1q, systemic lupus erythematosus, complement system, C4, SERPING1, family testing, monoclonal gammopathy, biomarker interpretation, immunology

The research team, led by investigators at the Institute of Hematology & Blood Diseases Hospital of the Chinese Academy of Medical Sciences and Peking Union Medical College in Tianjin, enrolled residual serum samples from 133 adults with suspected or established monoclonal gammopathies. Every sample was measured in parallel on the Kehua assay and Freelite, and 122 samples with sufficient remaining volume were additionally tested on the Siemens N Latex system. The cohort spanned the full clinical spectrum of plasma cell disorders, including IgG- and IgA-type myeloma of both light-chain classes, IgD-λ myeloma, free light-chain-only myeloma, Waldenström macroglobulinemia, AL amyloidosis, smouldering myeloma and monoclonal gammopathy of undetermined significance (MGUS).

The technical logic of the comparison matters as much as the numbers. Freelite, launched in 2001, uses sheep polyclonal antibodies raised against epitopes that are hidden when light chains are bound within intact immunoglobulins, and it is widely regarded as the reference assay behind the International Myeloma Working Group (IMWG) criteria. N Latex FLC, by contrast, employs a defined mixture of monoclonal antibodies on a nephelometric platform. The Kehua reagent takes a third route: anti-human free κ and free λ antibodies immobilized on latex particles, with antigen-antibody complex formation increasing turbidity that can be quantified on a routine automated chemistry analyzer—in this study a Beckman Coulter AU5800. That architecture could, in principle, bring sFLC testing into laboratories that already run standard biochemistry workloads without a separate nephelometer investment.

Precision came first in the validation hierarchy. Using low- and high-level commercial quality-control materials analyzed five times consecutively, the Kehua assay delivered within-run coefficients of variation below 5 percent for both κ and λ controls—ranging from 0.95 to 3.88 percent for FLC-κ across four independent run dates and from 0.67 to 4.66 percent for FLC-λ across two runs. All mean control values fell within manufacturer-specified acceptance windows, satisfying the less-than-10-percent precision goal set by the Clinical and Laboratory Standards Institute guideline EP05-A3. The authors are careful to note that this dataset documents short-term within-run performance across the reagent lots used during recruitment rather than a full long-term precision study.

Quantitative agreement against Freelite was the strongest result in the study. Pearson correlation coefficients reached 0.988 for FLC-κ, 1.000 for FLC-λ and 0.999 for the κ/λ ratio, with Lin’s concordance correlation coefficients between 0.983 and 0.999. Passing-Bablok regression, a robust method for estimating systematic and proportional bias, produced slopes close to unity for all three analytes—0.989 for κ, 1.077 for λ and 1.022 for the ratio—indicating near-identity across a concentration range spanning more than four orders of magnitude. Bland-Altman analysis showed mean relative differences of −3.75 percent for κ, +3.63 percent for λ and −7.34 percent for the ratio, with no concentration-dependent drift in relative bias.

Agreement with the N Latex system was also strong, with Pearson correlations of 0.991 to 0.998, but the regression analysis revealed a clinically relevant proportional bias in the κ/λ ratio. The Passing-Bablok slope of 0.733 means that at very high ratios the Kehua-derived value underestimates the N Latex result, while at low ratios it overestimates it. Because the involved/uninvolved sFLC ratio is embedded in IMWG diagnostic criteria—a ratio of 100 or more counts as a myeloma-defining biomarker when the involved light chain exceeds 100 mg/L—and in the 2/20/20 risk-stratification model for smouldering myeloma, the authors emphasize that absolute ratio values from Kehua and N Latex should not be used interchangeably around decision thresholds.

Qualitative concordance—the question of whether the assays classify the same samples as abnormal or normal—landed within the range reported for comparisons between the two imported assays themselves. Against Freelite, total concordance was 93.23 percent for FLC-κ, 90.98 percent for FLC-λ and 89.47 percent for the κ/λ ratio, with Cohen’s kappa values of 0.848, 0.799 and 0.675 respectively. Against N Latex, the corresponding figures were 91.80, 83.61 and 90.16 percent, with kappas of 0.836, 0.673 and 0.710. The largest discordance burden involved N Latex FLC-λ classification, where 20 of 122 samples (16.39 percent) were called differently—a pattern consistent with the known greater inter-method variability of λ measurement, partly attributable to polymerization artifacts that affect λ chains more frequently than κ.

Comparator-defined receiver-operating characteristic analysis added a practical layer: treating each imported method in turn as the qualitative reference, the Kehua assay achieved areas under the curve of 0.994 to 0.999 for reproducing elevated FLC-κ or FLC-λ calls, with Youden-optimal cut-offs closely matching the published upper reference limits of the comparator assays. For κ/λ ratio abnormality, AUCs were lower at 0.869 versus Freelite and 0.796 versus N Latex, reflecting the compounding of two assays’ individual biases in the composite biomarker. Notably, samples reaching the markedly abnormal ratio range used for the IMWG ≥100 biomarker were concordantly identified by all three platforms in this cohort, suggesting the residual discordance mainly affects borderline reference-interval calls rather than obviously extreme monoclonal patterns.

The authors frame the implementation implications conservatively. Multiple myeloma is the second most common hematological malignancy worldwide, and China’s disease burden has shown a particularly steep upward trajectory, with incidence rates projected to keep rising through 2050. Population screening programs such as iStopMM have demonstrated that subclinical light-chain MGUS is far more prevalent than previously estimated when sensitive sFLC assays are deployed. A serum test compatible with routine biochemistry analyzers could broaden laboratory access and support serial monitoring of oligosecretory myeloma and AL amyloidosis, though the study did not collect cost, distribution or workflow data, so affordability claims require separate health-economic validation.

The study’s limitations are clearly delineated: it was a single-center evaluation with a moderate sample size enriched for established disease; it was a method comparison rather than a complete analytical validation, leaving limits of detection, carry-over, lot-to-lot reproducibility and interference studies unassessed; only serum was tested, so findings cannot be extrapolated to urine or cerebrospinal fluid; and the manufacturer did not disclose the clonality or production route of the immobilized antibodies. Discordant calls were not adjudicated against an independent clinical gold standard. Still, the bottom line stands: with within-run precision under 5 percent, correlations above 0.99 against both imported systems, and kappa agreement of 0.67 to 0.85, the Kehua assay offers a credible domestic option for routine sFLC quantification—so long as laboratories maintain method-specific intervals and commit to a single platform for each patient’s longitudinal follow-up.

Subject of Research: Analytical validation of a domestic serum free light chain assay against two imported systems for plasma cell disorder testing

Article Title: Consistency and correlation of a domestic Kehua serum free light chain assay with two imported analytical systems

Article References: Ren, Y., Wang, S., Han, L., Wang, Y., Ren, Q., Wang, M., Xia, Y., & Zhu, G. (2026). Consistency and correlation of a domestic Kehua serum free light chain assay with two imported analytical systems. Frontiers in Oncology, 16, Article 1900671. https://doi.org/10.3389/fonc.2026.1900671

Image Credits: AI Generated

DOI: 10.3389/fonc.2026.1900671

Keywords: serum free light chain, multiple myeloma, monoclonal gammopathy, Kehua assay, Freelite, N Latex, immunoturbidimetry, method comparison, laboratory medicine, plasma cell disorders, diagnostic assay validation, AL amyloidosis

Fibrillary glomerulonephritis, first described in 1977, is characterized by the accumulation of non-amyloid fibrils, predominantly within the glomeruli, the microscopic filtering units of the kidney. Each glomerulus contains a sophisticated filtration barrier composed of fenestrated endothelial cells, the glomerular basement membrane, and podocytes, highly specialized epithelial cells whose interdigitating foot processes are joined by slit diaphragms built from proteins such as nephrin, podocin, and CD2-associated protein. When fibrillary deposits infiltrate the mesangium and capillary walls, this barrier is breached, and plasma proteins leak into the urine. The result is typically nephrotic-range proteinuria, microscopic hematuria, hypertension, and progressive loss of kidney function.

The patient arrived at the Department of Nephrology at Charles University and General University Hospital in Prague with bilateral leg swelling, blood in her urine, and an unintentional weight loss of 15 kilograms over two years. Her history included well-controlled hypertension, hypothyroidism, and rheumatoid arthritis diagnosed roughly five years earlier. Laboratory testing told a familiar story of glomerular injury: serum creatinine of 108 micromoles per liter, indicating mildly impaired kidney function; 24-hour urine protein excretion of 4.6 grams, well into the nephrotic range; serum albumin depressed to 30 grams per liter; and dysmorphic red blood cells in the urinary sediment, a signature of glomerular bleeding.

The kidney biopsy, performed on the fifth day of hospitalization, showed focal segmental mesangial expansion and increased mesangial cellularity, with 11 of 31 glomeruli globally sclerotic and two containing fibrocellular crescents. Interstitial fibrosis and tubular atrophy involved about a third of the renal cortex. Critically, Congo red and Saturn red stains were negative, ruling out amyloidosis, the great mimic of fibrillary disease. Immunofluorescence microscopy then revealed diffuse granular staining for IgG and complement C3 in the mesangium and along capillary walls, with moderate staining for lambda light chain and none for kappa, an apparent lambda-restricted pattern that immediately raised a diagnostic alarm.

Here the case becomes technically fascinating. Light-chain restriction on routine frozen-section immunofluorescence alone does not prove that deposits are truly monotypic. Unequal staining sensitivity or masking of immunoglobulin epitopes can produce a falsely restricted pattern, concealing a mixed population of antibodies beneath an apparently single one. To resolve the ambiguity, the team performed two additional investigations. IgG-subclass staining showed isolated IgG1 positivity, with IgG2, IgG3, and IgG4 all negative. Immunofluorescence on pronase-digested paraffin-embedded tissue, a technique that strips away masked epitopes, confirmed strong IgG and lambda staining with persistent absence of kappa. Concordant restriction to a single IgG subclass and a single light chain established a true monotypic IgG1-lambda phenotype.

Electron microscopy sealed the morphological diagnosis, revealing randomly oriented, non-branching fibrils measuring approximately 20 nanometers, accompanied by podocyte foot-process effacement, the structural correlate of heavy proteinuria. These dimensions distinguish fibrillary glomerulonephritis from immunotactoid glomerulopathy, which features larger microtubular deposits with hollow centers and more organized arrangement. Meanwhile, DNAJB9 immunohistochemistry showed strong, diffuse staining of the glomerular deposits. DNAJB9, a member of the DnaJ heat-shock protein family that functions as an endoplasmic-reticulum co-chaperone involved in protein folding, was identified through proteomic studies as an abundant component of fibrillary deposits. As a diagnostic biomarker it boasts roughly 98 percent sensitivity and over 99 percent specificity, making it indispensable for separating fibrillary glomerulonephritis from amyloidosis, immunotactoid glomerulopathy, and other organized-deposit diseases.

Monotypy carries serious clinical implications, because it raises the specter of monoclonal gammopathy of renal significance, a condition in which a hidden clone of B cells or plasma cells produces the very immunoglobulin that damages the kidney. Yet the systemic workup came back clean. Serum immunofixation detected no monoclonal protein, serum free light-chain concentrations and the kappa-to-lambda ratio were within reference ranges, hepatitis B and C were excluded serologically, and no hematological or other malignancy was identified. Bone marrow biopsy was deemed unnecessary given the absence of any circulating monoclonal protein. The authors are careful, however, to describe their findings as monotypic disease without demonstrable monoclonal gammopathy rather than claiming a clonal disorder was definitively excluded, since a small or non-secretory clone cannot be absolutely ruled out without marrow examination.

The association with rheumatoid arthritis adds another layer of rarity. In a multi-institutional cohort of 226 patients with fibrillary glomerulonephritis reported by Andeen and colleagues, only three had rheumatoid arthritis, roughly 1.3 percent, and none of 66 patients in the Mayo Clinic cohort had the disease. The mechanism linking chronic autoimmune inflammation to fibrillary glomerular injury remains uncertain. Persistent B-cell activation and dysregulated immunoglobulin production in autoimmune disorders could theoretically promote immunoglobulin-associated glomerular damage, and the presence of IgG1 and DNAJB9 within the deposits has fueled speculation that DNAJB9 may act as a putative autoantigen in an IgG-mediated autoimmune response. The authors emphasize, though, that fibrillary glomerulonephritis is not considered a conventional immune-complex complication of rheumatoid arthritis, and the coexistence should be interpreted as a rare clinicopathological association rather than proof of causation.

Treatment posed its own dilemma, since no standardized or definitively effective therapy for fibrillary glomerulonephritis exists. After discussion at a clinicopathological seminar, the team selected rituximab, a B-cell-depleting monoclonal antibody, based on limited evidence suggesting potential benefit when an immune-mediated process is suspected. The patient received one gram intravenously at baseline, a second gram two weeks later, and a third dose six months after initiation. The response was clinically meaningful: at 14 months, proteinuria had fallen from 4.6 grams to approximately 1.0 gram per 24 hours, and serum albumin had climbed from 30 to 38 grams per liter. Serum creatinine rose modestly to 133 micromoles per liter, indicating persistent kidney dysfunction without progression to kidney failure. The authors caution that this uncontrolled observation cannot establish causality or general efficacy.

The story ends somberly. The patient subsequently developed COVID-19 and died, with the infection documented as the direct cause of death, truncating follow-up at 14 months. The limitations of a single-patient report, incomplete intermediate laboratory data, absence of bone marrow examination and repeat biopsy, and restricted observation window mean that causality between rheumatoid arthritis and the kidney disease, the possible presence of a small hematological clone, and rituximab’s efficacy all remain open questions. Nevertheless, the case delivers a durable diagnostic lesson: establishing a truly monotypic fibrillary glomerulonephritis demands the integration of routine immunofluorescence, IgG-subclass assessment, pronase-digested paraffin-embedded immunofluorescence, DNAJB9 immunohistochemistry, and electron microscopy. Light-chain restriction alone is never enough, and monotypic deposits warrant careful hematological evaluation, even when, as here, the hunt for a culprit clone comes up empty.

Subject of Research: Monotypic IgG1-lambda fibrillary glomerulonephritis associated with rheumatoid arthritis without monoclonal gammopathy

Article Title: Case Report: Monotypic IgG1-λ fibrillary glomerulonephritis associated with rheumatoid arthritis

Article References: Nedoroscik, A., Moravcova, J., Manakova, L., Zakiyanov, O., Rysava, R., Tesar, V., & Kollar, M. (2026). Case Report: Monotypic IgG1-λ fibrillary glomerulonephritis associated with rheumatoid arthritis. Frontiers in Nephrology, 6, Article 1932311. https://doi.org/10.3389/fneph.2026.1932311

Image Credits: AI Generated

DOI: 10.3389/fneph.2026.1932311

Keywords: fibrillary glomerulonephritis, rheumatoid arthritis, monotypic deposits, DNAJB9, kidney biopsy, rituximab, monoclonal gammopathy, nephrotic syndrome, light-chain restriction, immunofluorescence, electron microscopy, podocytes

The research team followed 156 adults who developed invasive pneumococcal disease and required hospital care in Region Västra Götaland, Sweden, between 2018 and 2023. The median age of the patients was 70 years, a demographic in which both pneumococcal disease and blood malignancies become progressively more common. To determine whether the severe infection was merely bad luck or a signal of hidden vulnerability, the researchers performed detailed immunological workups. They measured antibody levels to detect deficiencies in humoral immunity, and they tested for the presence of M protein, a monoclonal immunoglobulin that serves as a well-established risk marker for blood cancer. A control group of 64 individuals, matched for age and sex but without invasive pneumococcal disease, provided a baseline for comparison.

The results were striking. Among the patients with invasive pneumococcal disease, one in four had M protein detectable in their blood. Monoclonal gammopathy of this kind can occur in established blood cancers, but it is also found in precursor states, conditions that do not yet meet the criteria for malignancy but can, in some patients, progress toward cancer over time. The examinations prompted by the study led to seven patients receiving a diagnosis of blood cancer, while another twelve were diagnosed with a precursor condition that may, in some cases, evolve into malignancy. In a group of just over 150 patients admitted for a severe bacterial infection, that represents a meaningful yield of previously silent disease.

The immune assessments also uncovered antibody deficiencies. Eight patients in the pneumococcal disease group were found to have immunodeficiency, and in seven of them, clinicians were able to start preventive treatment aimed at protecting against future severe infections. Such treatments can include replacement immunoglobulin therapy and tailored vaccination strategies, interventions that can substantially reduce the risk of recurrent invasive disease. By contrast, these abnormalities were considerably less common in the matched control group, reinforcing the idea that invasive pneumococcal infection is not randomly distributed but clusters in people whose immune surveillance is compromised.

The biological logic behind these findings is straightforward once the mechanics of pneumococcal immunity are considered. Streptococcus pneumoniae is an encapsulated bacterium, and its polysaccharide capsule is the principal target of protective antibodies. Clearance of the organism depends heavily on opsonization, the process by which antibodies coat the bacterium and mark it for destruction by phagocytic cells. People with low antibody levels, whether from a primary immunodeficiency or from the antibody-producing B-cell disorders that underlie many blood cancers, are therefore structurally less able to contain the bacterium when it colonizes the respiratory tract. What would be a mild or localized infection in an immunocompetent adult can become a systemic, hospital-requiring illness in someone whose humoral immunity is impaired.

M protein, the marker at the center of the study, is a monoclonal immunoglobulin produced by a single expanded clone of plasma cells or B cells. Its presence in the blood is the hallmark of a spectrum of disorders ranging from the benign-appearing monoclonal gammopathy of undetermined significance to smoldering and symptomatic myeloma. Because monoclonal gammopathies are common in older populations and often remain asymptomatic for years, most are discovered incidentally or not at all. The Gothenburg study suggests that severe pneumococcal disease may function as a clinical flag: when an older adult presents with invasive infection, the probability of finding an underlying monoclonal disorder is high enough that targeted testing could be worthwhile.

Currently, according to the researchers, these tests are not routinely performed after a severe pneumococcal infection. Tor Härnqvist, a doctoral student at the University of Gothenburg and an infectious disease physician at NU Hospital Group, and one of the lead authors of the study, points to the consequence of that gap. “Currently, these tests are not routinely performed after a severe pneumococcal infection. As a result, we may miss patients with undiagnosed blood cancer or immunodeficiency and therefore missing the opportunity to initiate treatment,” he says. The missed opportunity cuts in two directions: blood cancers such as myeloma are generally more treatable when identified before organ damage accumulates, and immunodeficiencies can be mitigated with preventive measures before the next invasive infection occurs.

The study carries implications for vaccination policy as well. Karin Bergman, a doctoral student in the same research group and an infectious disease physician at Södra Älvsborg Hospital, examined how the pneumococcal bacteria causing severe disease have shifted since the pneumococcal conjugate vaccine was introduced into the Swedish childhood vaccination program. Her analysis, part of a doctoral thesis she will soon defend at the University of Gothenburg, shows that the bacterial serotypes covered by the childhood vaccine have decreased sharply in circulation, but they have largely been replaced by other serotypes against which the childhood vaccine offers no protection. This serotype replacement is a well-documented ecological consequence of conjugate vaccination: eliminating vaccine-targeted strains from nasopharyngeal carriage opens ecological space for non-vaccine strains to colonize and spread.

Crucially, the serotypes now driving invasive disease in adults disproportionately affect older adults and individuals with underlying conditions, particularly cancer and compromised immune systems. This creates an uncomfortable alignment: the very populations most vulnerable to severe pneumococcal infection are those most likely to harbor undiagnosed blood cancer or antibody deficiency, and the circulating bacterial strains are precisely those that exploit gaps in adult immunity. “The results show that recommendations on pneumococcal vaccines for adults need to take into account which vaccines are used in children and which bacterial serotypes subsequently circulate in the community,” says Bergman. In other words, adult immunization strategy cannot be designed in isolation from the pediatric program, because the two are epidemiologically linked through the shifting serotype landscape.

Taken together, the findings support a concrete change in clinical practice. The researchers argue that screening for M proteins and antibody levels should be considered in adults who experience invasive pneumococcal disease, since the infection can reveal previously undiagnosed blood cancer and immunodeficiency. Such screening would involve relatively simple blood tests: quantitative measurement of serum immunoglobulins to identify antibody deficiencies, and protein electrophoresis or equivalent methods to detect monoclonal immunoglobulins. For a patient population that is already hospitalized and undergoing extensive workup, the incremental burden would be modest, while the potential benefit, catching a blood cancer or an immune deficiency that would otherwise remain hidden until it caused further harm, could be substantial. As populations age and serotype replacement continues to reshape pneumococcal epidemiology, the severe pneumonia that lands an older adult in the hospital may increasingly deserve to be read not only as an infection, but as a message from the immune system itself.

Subject of Research: Invasive pneumococcal disease as a marker of undiagnosed blood cancer and immunodeficiency in adults

Article Title: Pneumonia can reveal undiagnosed blood cancer

Article References: Pneumonia can reveal undiagnosed blood cancer. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: pneumococcal disease, pneumonia, blood cancer, M protein, immunodeficiency, monoclonal gammopathy, Streptococcus pneumoniae, antibody deficiency, pneumococcal vaccine, serotype replacement, University of Gothenburg, Scientific Reports

Monoclonal gammopathy of clinical significance, abbreviated MGCS, describes a situation in which a clone of plasma cells in the bone marrow produces an abnormal, monoclonal immunoglobulin. Unlike monoclonal gammopathy of undetermined significance, or MGUS, in which the abnormal protein is a harmless laboratory finding, MGCS means the monoclonal protein is actively damaging tissue. Depending on the properties of the antibody, that damage can take many forms: nerve injury, kidney disease, skin changes, amyloid deposition or, as in the cases examined here, muscle disease. The concept, formalized in a landmark 2018 position paper in the journal Blood, implies something clinically crucial: treating the plasma cell clone itself, rather than only the damaged organ, can halt or reverse the disease.

The first of the two conditions, scleromyxedema-associated myopathy, arises in patients with scleromyxedema, a rare sclerosing skin disease characterized by widespread papular and waxy thickened lesions caused by mucin deposits in the dermis. Scleromyxedema is itself almost always linked to an IgG monoclonal gammopathy, and its systemic complications can include neurological and muscular involvement. Muscle weakness in these patients has been reported sporadically since the 1960s and 1970s, but the pathological picture has remained fragmentary. The second condition, VAMMGAS, was only recently characterized in the European Journal of Neurology by a team including several of the same French investigators. It combines progressive muscle weakness, muscle stiffness, vacuolar changes visible on muscle biopsy and a monoclonal gammopathy, but without the characteristic skin disease of scleromyxedema.

To test whether these entities belong to a single disease family, the researchers performed a detailed side-by-side comparison of three patients: two with SAM and one with VAMMGAS. They examined the clinical course, electrophysiological findings, light-microscopic histopathology and, critically, ultrastructural features seen under the electron microscope. They then placed their observations against the backdrop of the published literature on both disorders and on related monoclonal gammopathy-associated myopathies, including sporadic late-onset nemaline myopathy, amyloid myopathy and newly described glycogen storage myopathies linked to plasma cell clones.

The comparison revealed striking common ground. All three patients showed progressive weakness predominantly affecting the proximal muscles, those closest to the trunk, such as the hip and shoulder girdles. Electromyography, the technique that records the electrical activity of muscle fibers through a needle electrode, showed prominent pathological spontaneous activity in all cases. This finding, which reflects irritable, unstable muscle membranes, indicates that the muscle fibers themselves are being injured, and it helps distinguish these myopathic processes from pure nerve disorders. In both conditions, the muscle biopsy showed a myopathy with features suggesting that autophagy, the cellular housekeeping system that digests and recycles damaged components, was not working properly. Autophagy is essential for muscle health; when it falters, fibers accumulate abnormal vacuoles and material that they cannot clear, a pattern familiar to neuromuscular specialists from genetic disorders such as X-linked myopathy with excessive autophagy and from drug toxicities such as colchicine myopathy.

Alongside the autophagy signature, the biopsies carried clear fingerprints of immune activation. The muscle fibers abnormally expressed HLA class I molecules, the same antigen-presenting machinery that flags cells to the immune system, and deposits of C5b-9, the membrane attack complex of the complement cascade, were found on the sarcolemmal membranes of the fibers. These are the kind of findings typically seen in immune-mediated myopathies, where antibodies and complement attack muscle directly or mark it for destruction. In other words, the muscle in both diseases shows simultaneous evidence of a failed intracellular waste-disposal system and an active immune assault on the fiber surface, a combination that is unusual and diagnostically provocative.

There were differences, too, and they may prove just as informative as the similarities. By definition, SAM occurs in the context of scleromyxedema, and the researchers note that the skin disease may occasionally appear only after the muscle symptoms have begun, a sequencing that can delay diagnosis. VAMMGAS, by contrast, is defined by prominent muscle stiffness. The monoclonal protein also differs in a subtle but potentially meaningful way: in SAM the underlying gammopathy is most commonly IgG of the kappa light-chain type, whereas IgG lambda appears to be more frequent in VAMMGAS. On histology, inflammatory infiltrates, actual clusters of immune cells within the muscle tissue, seem to be more characteristic of SAM, while VAMMGAS leans more heavily toward the vacuolar, autophagy-impaired picture. The authors propose that the two diseases occupy different positions on a spectrum running between autophagy dysfunction at one pole and inflammation at the other, with individual patients landing somewhere in between depending on the biology of their particular monoclonal protein.

Why would a single abnormal antibody cause such a strange mixture of cellular pathology? The study does not deliver a definitive mechanism, but the framework it suggests is biologically plausible. Monoclonal immunoglobulins or their light chains are known to interfere with lysosomal function and autophagic flux in other MGCS-related diseases; in amyloid light-chain cardiotoxicity, for example, lysosomal dysfunction and impaired autophagy are established drivers of tissue damage. At the same time, immune complexes formed by monoclonal antibodies can activate complement, explaining the C5b-9 deposits on muscle membranes. Fibroblast growth factor 2 and transforming growth factor beta signaling have been invoked in the skin fibrosis of scleromyxedema, and TGF-beta is also known to epigenetically regulate autophagy, hinting at possible molecular bridges between the fibrosing, inflammatory and autophagic components of the syndrome.

The therapeutic implications may be the most consequential part of the work. Because both conditions appear to sit within the MGCS framework, they seem to respond to two complementary treatment strategies: immunomodulatory approaches, including intravenous immunoglobulin and plasma exchange, and clone-directed therapies that target the plasma cells producing the offending monoclonal protein. Intravenous immunoglobulin has long been a mainstay for the skin disease of scleromyxedema, and plasma exchange has been used successfully in refractory cases, while plasma cell-directed regimens have shown benefit in monoclonal gammopathy-associated scleromyxedema. Recognizing SAM and VAMMGAS as related MGCS manifestations gives clinicians a rationale for combining these approaches and for monitoring the monoclonal protein as a marker of disease activity, rather than treating the muscle in isolation with nonspecific immunosuppression.

For patients, the practical message is one of awareness. Unexplained progressive proximal weakness, especially when accompanied by muscle stiffness, thickened or waxy skin, or an abnormal protein band on serum electrophoresis, should prompt evaluation by a neuromuscular specialist and a hematologist together. The authors emphasize that recognizing the overlapping clinical, neurophysiological and histological features of SAM and VAMMGAS can shorten the diagnostic odyssey and open the door to treatments that address the root cause. With only a handful of cases described worldwide, much remains to be learned, and the researchers themselves frame their conclusions as hypothesis-generating rather than definitive. But the idea that a lone clone of antibody-producing cells can push muscle fibers simultaneously into autophagic failure and immune-mediated injury, and that this process can be caught and treated, marks a genuine step forward in the understanding of rare immune-muscle disease.

Subject of Research: Scleromyxedema-associated myopathy and VAMMGAS as monoclonal gammopathy-associated muscle diseases

Article Title: Scleromyxedema-Associated Myopathy and Vacuolar Myopathy with Monoclonal Gammopathy and Stiffness (VAMMGAS) as manifestations of Monoclonal Gammopathy of Clinical Significance (MGCS): a disease spectrum between autophagy dysfunction and inflammation

Article References: Nicoletti, T., Benveniste, O., Battistella, M., Mahevas, T., Arnulf, B., Stojkovic, T., Staedler, K., Maisonobe, T., Letournel, F., Romero, P., Malfatti, E., Vignon, M., Nadaj-Pakleza, A., Labella, B., Lacene, E., Brochier, G., Evangelista, T., & Leonard-Louis, S. (2026). Scleromyxedema-Associated Myopathy and Vacuolar Myopathy with Monoclonal Gammopathy and Stiffness (VAMMGAS) as manifestations of Monoclonal Gammopathy of Clinical Significance (MGCS): a disease spectrum between autophagy dysfunction and inflammation. Journal of Neurology, 273(10), Article 633. https://doi.org/10.1007/s00415-026-14169-2

Image Credits: AI Generated

DOI: 10.1007/s00415-026-14169-2

Keywords: monoclonal gammopathy, MGCS, scleromyxedema, VAMMGAS, vacuolar myopathy, autophagy, muscle weakness, HLA class I, complement C5b-9, intravenous immunoglobulin, plasma exchange, neuromuscular disease