Noonan syndrome with multiple lentigines

Noonan syndrome with multiple lentigines, abbreviated NSML, is a rare autosomal dominant, multisystem disease caused by a mutation in the PTPN11 gene, which encodes a protein tyrosine phosphatase. It belongs to the group of Ras/MAPK pathway syndromes, the RASopathies. The disease is a complex of features, mostly involving the skin, skeletal and cardiovascular systems, and these may or may not be present in every patient. How the mutation produces each symptom is not well understood and research is continuing. Noonan syndrome is caused by a different missense mutation in the same gene and is fairly common, whereas no epidemiological data exist for NSML.