Phenotypic variability in a three-generation Northern Irish family with Sotos syndrome

Sotos syndrome is an overgrowth disorder with autosomal dominant inheritance caused by mutations and deletions in the nuclear receptor Set domain-containing protein 1 gene. In general, affected individuals have an advanced bone age, macrocephaly, characteristic facial gestalt and learning difficulties. Genotype-phenotype correlations are unclear. Full penetrance is seen and 95% of cases are de novo. Here, we report a three-generation pedigree, with at least eight affected individuals, shown to harbour the nuclear receptor Set domain-containing protein 1 missense mutation c. 6115C>T. To our knowledge, this is the largest Sotos family reported. The observed phenotype is extremely variable, thus highlighting the clinical heterogeneity that may occur.