WNK2 and Noonan syndrome: Mutations in genes encoding proteins in the Ras-mitogen-activated protein kinase (MAPK) signaling pathway cause Noonan syndrome and other related disorders, such as Noonan syndrome with multiple lentigines (formerly known as LEOPARD (lentigines, electrocardiographic conduction abnormalities, ocular hypertelorism, pulmonary stenosis, abnormal genitalia, retarded growth, and deafness) syndrome), cardiofaciocutaneous syndrome, and Costello syndrome.