[SOS1 mutation: a new cause of Noonan syndrome]

Noonan syndrome, characterized by short stature, facial anomalies, heart disease and cryptorchidism in males, is an autosomal dominant, genetically heterogeneous disease. Approximately 50 % of Noonan syndrome cases are caused by gain-of-function mutations in PTPN11, encoding the tyrosine phosphatase (SHP2) and 5 % are caused by KRAS mutations. Recently, a new mutation in SOS1 gene has been identified in approximately 20 % of cases of Noonan syndrome without PTPN11 mutation. That difference in genotype has a relationship with phenotype that we must investigate. We report a case of Noonan syndrome due to an SOS1 mutation; we describe his phenotype and subsequent outcome.