Noonan syndrome type 4

Noonan syndrome type 4

A relatively common autosomal dominant disorder (OMIM:610733) characterised by dysmorphic facies, hypertelorism, short stature, cardiac anomalies, deafness, motor delay, bleeding diathesis and pulmonary valve disease. It may rarely be associated with juvenile myelomonocytic leukaemia.

Molecular pathology
Caused by defects of SOS1, which encodes a guanine nucleotide exchange factor for RAS proteins, a family of membrane proteins that bind guanine nucleotides and participate in signal transduction pathways.