Das Noonan-Syndrom

Noonan syndrome is an important dysmorphic syndrome. The main clinical features are pulmonary stenosis, short stature and typical face. The inheritance is autosomal dominant with mutations in the PTPN11 gene in 40-50% of the patients. If molecular genetic testing is normal, differential diagnoses such as CFC or Costello syndrome have to be considered, as well as Turner- or Leopard syndrome and neurofibromatosis 1. In patients with Leopard syndrome mutations in PTPN11 gene can be found, whereas patients with CFC or Costello syndrome can have mutations of the same pathway in different genes (K-RAS, H-RAS, B-RAF, MEK1/2). It is of note that normal mental development in general is present in patients with Noonan syndrome whereas patients with CFC or Costello syndrome have a severe mental delay. Furthermore patients with Noonan and Costello syndrome have a higher risk for malignancies.