NF1 is caused by pathogenic variants in the NF1 gene, an unusually large gene located on chromosome 17 that carries the instructions for neurofibromin, a protein widely described as a tumor suppressor. Neurofibromin’s principal job is to act as a brake on cellular growth signaling, specifically by accelerating the conversion of the RAS protein from its active to its inactive state, thereby dampening the mitogen-activated protein kinase, or MAPK, pathway. When that brake fails, cells in nerve sheaths, skin pigment systems, bone, and brain can proliferate abnormally, producing the diverse constellation of features clinicians recognize: café-au-lait macules, freckling in skin folds, Lisch nodules in the iris, skeletal abnormalities, learning difficulties, and an elevated risk of benign and malignant tumors.

The Shanghai cohort offered an unusually rich window into that complexity. Every child in the study underwent genetic testing, and researchers painstakingly curated both the genetic and phenotypic data, using SPSS, GraphPad Prism, and Python for statistical analysis and generating growth curves and variant distribution maps from the integrated dataset. What emerged was a picture of remarkable heterogeneity: patients exhibited a broad range of multisystem manifestations, with skeletal abnormalities and developmental or intellectual impairments standing out as particularly common and as features showing notable differences between the sexes.

Among the most consequential findings is the study’s contribution to understanding growth in children with NF1. Males in the cohort had significantly lower height standard deviation scores than females, and when the team constructed P50, or median, growth curves for their patients, those curves sat consistently below the reference values for healthy children of the same population. This is not a trivial statistical curiosity. Height assessment is one of the most routine measurements in pediatrics, and for children with NF1 it has long been a source of uncertainty: is a child simply short for their family, or is the disorder itself reshaping their growth trajectory?

The new sex-specific growth curves directly address that uncertainty. By incorporating longitudinal growth data from childhood into the analysis, the researchers built a precise reference standard tailored to children with NF1, giving clinicians a benchmark against which growth abnormalities can be evaluated with far more confidence than was previously possible. Earlier studies have established that height impairment in NF1 is characterized by decreased pubertal growth velocity in both sexes, and growth hormone deficiency has been documented in some patients even without suprasellar brain lesions, but the field has lacked contemporary, population-matched charts of the kind this cohort now provides. The implications run in both directions: clinicians will be better able to identify children whose growth deviates even from the NF1-specific curve, signaling a possible endocrine complication that warrants investigation, while also sparing families unnecessary anxiety when a child is tracking appropriately along the disorder’s own, slightly lower, trajectory.

On the genetic side, the study’s findings illuminate how different classes of NF1 variants translate into different clinical realities. Truncating variants, which introduce premature stop signals and typically render the neurofibromin protein nonfunctional, were the most common mutation type in the cohort, accounting for 60.8 percent of cases. But the correlations the researchers uncovered went beyond simple frequency counts. Patients harboring single amino acid variations, in which one building block of the protein is swapped for another without truncating it, exhibited a significantly higher prevalence of short stature than patients with truncating variants. This counterintuitive result, in which a seemingly milder molecular defect produces a more pronounced growth phenotype, echoes prior reports of specific missense mutations affecting the p.Arg1809 residue being associated with Noonan syndrome features, including short stature and pulmonic stenosis, and suggests that altered, rather than simply absent, neurofibromin function may perturb growth signaling in distinctive ways.

Splice variants, which disrupt the precise editing of the gene’s messenger RNA, told a different story. In this cohort, splice variants were associated with unidentified bright objects, known as UBOs, the mysterious hyperintense spots that appear on brain MRI scans of many children with NF1 and have been linked in prior neuroimaging natural history studies to clinical features, and with abnormalities of the optic nerve, the structure most vulnerable to optic pathway gliomas, low-grade tumors that are among the most feared complications of pediatric NF1. If confirmed in larger and more diverse populations, such associations could eventually guide surveillance strategies, allowing clinicians to prioritize MRI screening or ophthalmologic monitoring for children whose genetic test results fall into higher-risk variant classes.

The cohort’s genetic architecture also yielded fundamental insights into how NF1 enters a family in the first place. Among the 229 patients for whom the parental origin of the variant was known, a striking 77.29 percent carried de novo variants, meaning the mutation arose spontaneously in the child rather than being inherited from a parent. This high proportion of fresh mutations is consistent with NF1’s status as one of the classic de novo mutation disorders in human genetics, and it carries real counseling weight: parents of a child with a confirmed de novo variant face a low recurrence risk in future pregnancies, whereas an inherited variant implies a one-in-two risk for each subsequent child. The study also expanded the known variant landscape, identifying 37 novel NF1 variants not previously cataloged, adding to the growing global database that underpins accurate molecular diagnosis. The processed genotype and phenotype data, with patient information anonymized, have been made publicly available on GitHub, reflecting a growing commitment to open data in rare disease research, although raw sequencing data remain restricted by institutional and ethical privacy protections.

The broader significance of the work lies in how it reframes NF1 as a disorder whose clinical course can, at least in part, be read from its genetic code. Revised international diagnostic criteria, published in 2021, now allow a molecular diagnosis of NF1 even in young children who have not yet developed enough clinical features to meet the classic criteria, making genetic testing an increasingly front-line tool. Studies like this one, conducted over more than a decade at a single center with consistent methodology, provide exactly the kind of large, internally coherent evidence base that such testing depends on. They also lay groundwork for the next therapeutic chapter: with MEK inhibitors already transforming the treatment landscape for inoperable NF1-related plexiform neurofibromas, a deeper understanding of how specific variant classes drive specific downstream pathways may eventually inform which patients benefit most from which targeted agents.

Challenges remain, as the researchers themselves acknowledge through the careful framing of their conclusions. Single-center cohorts, however large, reflect one population and one clinical referral pattern, and genotype-phenotype correlations in NF1 are probabilistic rather than deterministic; even within a single variant class, two children can follow dramatically different courses. Modifier genes, stochastic developmental events, and environmental factors all likely contribute to the variability that makes NF1 so difficult to predict. Yet the Shanghai study moves the field measurably forward. It documents, in 301 children followed across 12 years, the breadth of the disorder’s multisystem phenotype; it quantifies sex-related differences in skeletal and neurodevelopmental features; it delivers the first sex-specific growth references built from contemporary childhood data; and it ties variant classes to growth failure, brain imaging findings, and optic nerve abnormalities with statistical rigor. For the families of the estimated one in every 2,500 to 3,000 children born with NF1 worldwide, and for the clinicians who care for them, the message is one of cautious optimism: the era of precisely mapping this unpredictable disease, and of using that map to anticipate and treat its complications, is gathering speed.

Subject of Research: Genotype-phenotype correlations and growth characteristics in pediatric neurofibromatosis type 1

Article Title: Phenotypic and genotypic characteristics of pediatric patients with neurofibromatosis type 1: a 12-year single-center cohort study

Article References: Li, Z.-Y., Li, X., Wen, T., Feng, B.-Y., Song, Y., Hu, J.-Y., Yu, T.-T., Yao, R.-E., & Wang, X.-M. (2026). Phenotypic and genotypic characteristics of pediatric patients with neurofibromatosis type 1: a 12-year single-center cohort study. World Journal of Pediatrics. https://doi.org/10.1007/s12519-026-01092-9

Image Credits: AI Generated

DOI: 10.1007/s12519-026-01092-9

Keywords: neurofibromatosis type 1, NF1 gene, genotype-phenotype correlation, pediatric genetics, short stature, growth charts, de novo variants, truncating variants, splice variants, optic pathway glioma, neurofibromin, MAPK pathway

The research team, led by investigators at Soochow University’s Suzhou Medical College and the Children’s Hospital of Soochow University, designed the study around a cohort of children who had already undergone the most rigorous diagnostic sequencing available. Trio-based whole-exome sequencing, in which the affected child and both parents are sequenced to identify de novo and inherited variants, has become the gold standard for unraveling unexplained genetic conditions. Yet in many cases of short stature it returns no definitive answer. The researchers therefore turned their attention to the children left in this diagnostic gap, hypothesizing that their condition might arise from the collective effect of multiple rare variants distributed across growth-related genes rather than from a single damaging mutation in one gene. To test this idea, they compared the 112 undiagnosed patients against two control groups: 352 healthy adults of normal stature and 4,327 internal samples drawn from the Exome Aggregation Consortium database, one of the largest publicly available catalogs of human protein-coding variation.

The analytical engine of the study was an optimized version of TRAPD, a framework for testing rare variants using public data. Gene-based burden testing works by collapsing all of the rare, functionally significant variants within a single gene and asking whether cases carry a greater burden of such variants than controls would be expected to. This approach has substantially more statistical power than testing variants one at a time, because individual rare variants are too uncommon for any single one to reach significance in a modest cohort. The team applied the method under both dominant and recessive inheritance models, and the results were striking in their breadth. Under a dominant model, in which a single copy of a damaging variant is sufficient to influence the trait, 3,907 genes showed significant enrichment of rare variants at a threshold of P less than 0.05. Under a recessive model, which requires both copies of a gene to carry damaging variants, 85 genes were significantly enriched. Among the top ten most significantly associated genes identified through the primary modeling, four stood out with extraordinarily strong signals: FCGBP, FRAS1, MPDZ, and OBSCN, each reaching significance levels beyond P less than 1 × 10⁻⁹.

Each of the four implicated genes offers a distinct window into the biology of linear growth. OBSCN encodes obscurin, a gigantic cytoskeletal protein that scaffolds the sarcolemma and sarcoplasmic reticulum in muscle cells and helps organize muscle metabolism. Its connection to stature may run through the mechanical and metabolic dialogue between muscle and bone during development, a relationship increasingly recognized as a driver of skeletal growth. FRAS1 encodes a component of the extracellular matrix that is essential for the structural integrity of basement membranes, the thin sheets of specialized extracellular matrix that underlie epithelial tissues; mutations in FRAS1 are classically associated with Fraser syndrome, a congenital disorder that can include skeletal abnormalities. MPDZ is a scaffolding protein known to promote DLL4-induced Notch signaling during angiogenesis, the formation of new blood vessels, a process on which the vascular supply of the growth plate depends. FCGBP, or IgGFc-binding protein, is a large mucin-associated protein produced by goblet-like cells in the gut that participates in mucosal barrier function and wound healing, an intriguing connection given emerging evidence linking gut health and inflammation to growth outcomes in children.

To make sense of how these and the other enriched genes might converge on growth, the researchers performed functional enrichment analyses using Kyoto Encyclopedia of Genes and Genomes and Gene Ontology pathway frameworks. The results revealed significant enrichment in four metabolic and signaling pathways: steroid hormone biosynthesis, ascorbate and aldarate metabolism, pentose and glucuronate interconversions, and porphyrin metabolism. The steroid hormone biosynthesis signal is perhaps the most intuitive, given the central role of hormones from the hypothalamic-pituitary-gonadal and adrenal axes in regulating the growth plate. The ascorbate-related findings carry particular weight in light of recent research showing that vitamin C epigenetically controls osteogenesis and bone mineralization, meaning that the pathways governing ascorbate metabolism could directly influence how cartilage and bone mature. Pentose and glucuronate interconversions, meanwhile, connect to glycosaminoglycan synthesis and extracellular matrix remodeling, both critical for growth plate architecture.

The pathway picture also reinforces the idea that linear growth is not simply a matter of growth hormone and insulin-like growth factor acting on cartilage, but rather an integrated output of hormonal signaling, extracellular matrix integrity, and muscle-skeletal mechanical interaction. Obscurin, FRAS1, and MPDZ each appeared in multiple enriched pathways, suggesting that these genes occupy hub positions within a network whose perturbation impairs growth. This systems-level view aligns with a broader paradigm shift in growth biology, in which height is understood as a quantitative trait shaped by the coordinated activity of hundreds of genes across multiple tissue types. It also provides a mechanistic rationale for why sequencing a limited panel of canonical growth genes—SHOX, NPR2, NPPC, ACAN, IHH, FGFR3, and others—leaves so many children without a diagnosis. If susceptibility is distributed across the genome, then single-gene analysis will inevitably miss much of the picture.

The technical significance of the study lies in part in its adaptation of burden testing to a clinical cohort using public control data. Traditionally, association studies demand large, locally sequenced control cohorts, a resource that few clinical centers possess. The TRAPD framework circumvents this obstacle by allowing researchers to compare the variant burden observed in their patient exomes against allele frequency expectations derived from public repositories such as the Exome Aggregation Consortium. The optimized implementation used here accounted for gene-specific mutation rates and variant annotation, allowing a fair comparison across genes of very different sizes and constraint profiles. The approach had already proven useful for identifying rare-variant contributions to other quantitative traits, and this study demonstrates its utility in a pediatric endocrinology setting, where cohorts are inherently limited in size because short stature of unexplained origin, while common in clinics, is heterogeneous and difficult to recruit in the thousands.

Clinically, the findings carry several implications. First, they suggest that children with ISS may harbor a polygenic load of rare variants that current diagnostic frameworks do not capture, and that gene-based burden testing could become a complementary tool in the evaluation of such patients, layered on top of standard trio sequencing. Second, the identification of steroid hormone biosynthesis as an enriched pathway hints that some children may have subtle, subclinical perturbations of hormonal metabolism that standard endocrine workups do not detect, opening the possibility of more refined metabolic phenotyping. Third, the involvement of extracellular matrix and muscle-related genes raises the prospect of therapeutic strategies aimed not at the growth hormone axis itself but at the structural and mechanical environment of the growth plate. The authors are careful to frame these as susceptibility genes rather than deterministic causes, which is consistent with the variable expressivity expected of a quantitative trait.

The study also sits within a growing literature that connects growth to biology far beyond the skeleton. Recent work has documented gut microbiome dysbiosis with enriched pro-inflammatory species in children with idiopathic short stature, and the FCGBP finding provides a possible genetic thread connecting mucosal immune function to growth outcomes. Similarly, the observation that obscurin and its paralog OBSCN-family relatives maintain sarcolemmal integrity and muscle metabolism dovetails with evidence that skeletal muscle growth differences across individuals have a genetic basis that parallels bone growth. Height, in this emerging framework, is a trait of the whole organism: it depends on vasculature supplying the growth plate, on basement membranes structuring developing tissues, on muscle generating the mechanical signals that sculpt bone, and on hormones whose synthesis depends on metabolic pathways not traditionally considered in the endocrinology clinic.

The researchers acknowledge that their findings represent association rather than proof of causation, and that functional validation in model systems will be needed to confirm how rare variant burdens in OBSCN, FCGBP, FRAS1, and MPDZ translate into altered growth. Larger cohorts and replication in independent populations will also be essential to consolidate the signals. Nevertheless, the study represents a meaningful expansion of the known genetic landscape of isolated short stature, moving the field from a catalogue of single-gene defects toward an appreciation of the polygenic architecture that underlies one of the most common referrals in pediatric endocrinology. For the many families who leave genetics clinics without an answer, the message is that their child’s short stature may not be idiopathic at all—it may simply reflect a pattern of rare genetic variation that medicine is only now learning to read.