A novel NSD2 pathogenic variant in a Chinese patient with Rauch-Steindl syndrome: a case report

Rauch-Steindl syndrome (RSS) is a very rare autosomal dominant disorder caused by pathogenic variants in the NSD2 gene, characterized by dysmorphic facial features, prenatal and postnatal growth retardation, and variable developmental delay. We report the case of a 16-month-old Han Chinese girl who presented with typical features of RSS, including prenatal and postnatal growth failure, low body mass index, global developmental delay, expressive language impairment, infantile feeding difficulties, and distinctive dysmorphic facies (triangular face, broad forehead, high anterior hairline, deep-set eyes, full cheeks, thin and high nasal bridge, thick lower lip vermilion). She also exhibited mildly increased muscular tone in the lower limbs, transient recurrent respiratory infections, and a persistent atrial septal defect (ASD). Whole-exome sequencing identified a novel de novo heterozygous nonsense variant, NSD2 (NM_001042424.3): c.1466 C > G (p.Ser489Ter), in exon 6 on chromosome 4, which was classified as pathogenic according to ACMG guidelines. Notably, the patient exhibited an ASD that persisted through follow-up beyond 31 months of age, a feature not previously documented in RSS. Thus, we report a novel pathogenic NSD2 variant alongside the presence of ASD in this individual, a feature not previously documented in RSS.