Constitutional NRAS mutations are rare among patients with Noonan syndrome or juvenile myelomonocytic leukemia.

Recently, germline mutations of NRAS have been shown to be associated with Noonan syndrome (NS), a relatively common developmental disorder characterized by short stature, congenital heart disease, and distinctive facial features. We report on the mutational analysis of NRAS in a cohort of 125 French patients with NS and no known mutation for PTPN11, KRAS, SOS1, MEK1, MEK2, RAF1, BRAF, and SHOC2. The c.179G>A (p.G60E) mutation was identified in two patients with typical NS, confirming that NRAS germline mutations are a rare cause of this syndrome. We also screened our cohort of 95 patients with juvenile myelomonocytic leukemia (JMML). Among 17 patients with NRAS-mutated JMML, none had clinical features suggestive of NS. None of the 11 JMML patients for which germline DNA was available had a constitutional NRAS mutation.