Abnormal growth in noonan syndrome: the challenge of optimal therapy.

Noonan syndrome (NS) is a phenotypically heterogeneous condition frequently associated with short stature. Genetic investigations have identified mutations in several genes, e.g. PTPN11, KRAS, RAF and SOS1 in patients with the NS phenotype and related disorders such as LEOPARD, Costello and Cardiofacio- cutaneous syndromes. In NS, PTPN11 mutations are present in 29-60% of cases. The degree of short stature does not associate closely with the presence of a mutation; however, some PTPN11-positive patients have decreased growth hormone (GH)-dependent growth factors consistent with mild GH insensitivity. GH therapy induces short-term increases in height velocity over 1-3 years, and is likely to improve adult height.