Mutations associated with Noonan syndrome alone include CBL, BRAF, KRAS, LZTR1, MAP2K1 (MEK1), NRAS, PTPN11, RAF1, RIT1, SOS1 and SOS2 (Riller and Rieux-Laucat, 2021; Leoni et al., 2022). Here, MAP2K1 is linked to Noonan syndrome.