Contributor: Gordon K. Klintworth
Noonan syndrome (female pseudo-Turner syndrome, male Turner syndrome, Turner phenotype with normal karyotype, pterygium coli syndrome, OMIM # 163950) is an inherited developmental syndrome that was first documented by Noonan and Ehmke in 1963. The phenotype  is clinically and genetically heterogenous and is characterized by a short stature, cardiac defects, skeletal malformations, pterygium colli, unusual facies and a low hairline. Many affected individuals suffer from a bleeding diathesis. Ophthalmic manifestations include ptosis, hypertelorism, down-slanting palpebral fissures, epicanthal folds [epicanthal fold], keratoconus, and colobomata [coloboma]. Corneal thinning leading to a spontaneous corneal rupture has also been reported. Noonan syndrome is due to a mutation in the PTPN11 gene. Noonan syndrome is allelic with LEOPARD syndrome. The differential diagnosis includes Turner syndrome, but the karyotype is normal.