Noonan syndrome and its related disorders.

The diagnosis of Noonan syndrome still rests on its clinical features. There are several syndromes to consider in the diagnosis of Noonan syndrome. These include cardio-facial-cutaneous syndrome, LEOPARD syndrome, neurofibromatosis-Noonan syndrome and Costello syndrome. The facial appearance and part of the clinical features of these syndromes are very similar to Noonan syndrome. Molecular research likely will elucidate whether these syndromes are variations of Noonan syndrome or etiologically different disorders.