There is a lack of comprehensive epidemiological data and mutation detection rates; genes associated with Noonan syndrome include PTPN11 (found in approximately half of NS patients); besides the known genes (BRAF, KRAS, MAP2K1, MRAS, NRAS, PTPN11, RAF1, RASA2, RIT1, RRAS2, SOS1, SOS2, LZTR1), several additional genes have been identified in fewer than ten individuals, each associated with a Noonan-syndrome-like phenotype [3,17]. Here, SOS2 is linked to Noonan syndrome.