Identification of a PTPN11 hot spot mutation in a child with atypical LEOPARD syndrome.

LEOPARD syndrome (LS) is an autosomal dominant inherited disorder primarily caused by mutations in the PTPN11, RAF1 and BRAF genes. Characteristic features include lentigines, craniofacial dysmorphism, myocardium or valve abnormalities, eletrocardiographic conduction defects and deafness. LS, neurofibromatosis type 1, Noonan syndrome and Legius syndrome are a group of highly overlapped disorders termed 'RASopathies'. Therefore, clinical discrimination between these syndromes represents a huge challenge. The present study reports a young child diagnosed with LS via identification of a common p.Thr468Met mutation in PTPN11. Taking into account two Taiwanese LS cases with an identical mutation, Thr468Met is likely to be the most prevalent mutation in the Chinese population. Furthermore, this study suggests that a clinical diagnosis of LS should be considered for individuals with congenital cardiac defects and atypical lentigines (i.e., light brown freckles) scattered particularly on the face.