Expanding the Clinical Spectrum of Sotos Syndrome in a Patient with the New “c.[5867T>A]+[=]”; “p.[Leu1956Gln]+[=]” NSD1 Missense Mutation and Complex Skin Hamartoma

Sotos syndromeis one of the most common overgrowth diseases and it predisposes patients to cancer, generally in childhood. The prevalence of this genetic disorder is 1:10,000–1:50,000, and it is characterized by wide allelic heterogeneity, with more than 100 different known mutations in the nuclear receptor-binding SET domaincontaining protein 1 (NSD1) gene. Most of these alterations are deletions and common micro-deletions with haploinsufficiency. Singular variants are missense mutations. The present study reports a case of a 4-year-old boy with specific clinical features of Sotos syndromeand a particular complex skin hamartomaon the right femoral side, in addition to other minor findings, such as a “ cafe-au-lait” spoton the right hemithorax and syndactylyof the second and third right toes. NSD1 gene analysis identified a de novo missense mutation, “c.[5867T>A]+[=]”; “p.[Leu1956Gln]+[=]”, that was not previously described in the literature. This mutation was localized to the functional domain of the gene and was likely the cause of Sotos syndromein our patient. We also compared aspects of our patient’s condition with the clinical features of tuberous sclerosis(TSC), which is an autosomal neurocutaneous syndrome caused by mutations in the TSC1/ TSC2genes. These genes control cell growth and cell survival. This disorder is characterized by hamartomasin multiple organ systems, several coetaneous abnormalities, epilepsy, and increased risk of several types of tumors.