Largest Pediatric Neurofibromatosis Study Reveals How Gene Variants Shape Growth and Disease Severity

Neurofibromatosis type 1, one of the most common genetic disorders affecting the human nervous system, has long defied clinicians’ attempts to predict how it will unfold in any given child. Now, a 12-year study from Shanghai Children’s Medical Center has produced one of the most detailed portraits to date of how the condition presents in childhood, tracking 301 pediatric patients from July 2013 to August 2025 and pairing their clinical journeys with an exhaustive genetic analysis. The research, published in the World Journal of Pediatrics, confirms that NF1 is far more than a skin-deep disorder of coffee-colored birthmarks, revealing a strikingly multisystem disease with measurable differences between boys and girls, and offering new genotype-phenotype correlations that could sharpen diagnosis and monitoring for years to come.

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