MAP2K1 and Noonan syndrome: So far, heterozygous mutations in nine genes (PTPN11, KRAS, NRAS, SOS1, RAF1, BRAF, SHOC2, MEK1, and CBL) in the Ras-MAPK signaling pathway cause NS or closely related conditions, comprising LS, Noonan-like syndrome with loose anagen hair (NS/LAH, OMIM 607721), and the recently documented “CBL mutation associated” syndrome [5,6].