Supplementary Material for: Late diagnosis of a 3p26.3p25.2 microduplication in a young adult with mild neurodevelopmental features: a case report and literature review

Introduction Intellectual disability with mild dysmorphic features may be attributed to perinatal complications such as neonatal hypoxia. However, chromosomal abnormalities may underline these phenotypes. We report a case with rare copy number variants that are likely to have neurodevelopmental relevance. Case presentation A 21-year-old female presented with mild dysmorphic features, and intellectual disability that was initially attributed to neonatal hypoxia (i.e., fetal distress). Array-CGH analysis revealed a pathogenic microduplication at 3p26.3p25.2 and a microduplication of uncertain significance at 2q11.2. The duplicated regions encompass several genes with known neurodevelopmental relevance, including TRNT1, CRBN, GRM7, SETD5, BRPF1, ARPC4, CHL1, CNTN6, and LMAN2L. This case is the first clinical report of an adult with this specific chromosomal duplication. Conclusion This case provides valuable insights into the long-term natural history and clinical evolution of these duplications. It underscores the importance of genetic evaluation in individuals with intellectual disability and subtle clinical features, when the morbidities are not definitively attributable to postnatal or perinatal events.