MAP2K1 and Noonan syndrome: Individuals with Noonan Syndrome (MIM: 163950) comprise ~50% of all RASopathy cases and mutations have been observed in multiple genes, including PTPN11/SHP2, SOS1, SHOC2, KRAS, NRAS, LZTR1 (MIM: 600574), RAF1/CRAF, and MAP2K1/MEK1 [13,21,23].