Atypical Sotos syndrome caused by a novel splice site variant

Abstract Sotos syndrome is usually caused by haploinsufficiency of NSD1 ; it is characterized by overgrowth, craniofacial features, and learning disabilities. We describe a boy with Sotos syndrome caused by a splicing variant (c.4378+5G>A). The clinical manifestations included severe connective tissue involvement, including joint hypermobility, progressive scoliosis, pectus deformity, and skin hyperextensibility; no overgrowth was observed.