Popliteal pterygium syndrome

Popliteal pterygium syndrome, shortened to PPS, is a rare inherited genetic disorder marked by distinctive features of the face and skull, the muscles and bones, and the genitourinary system. It is mainly caused by a mutation of the IRF6 gene and follows an autosomal dominant pattern of inheritance. Typical features include webbing of skin behind the knee, cleft lip or palate and fused fingers or toes, and the severity and mix of features vary between affected people. The source gives an approximate incidence of 1 in every 300,000 live births. Trelat first described the condition in 1869, and Gorlin and colleagues named it in 1968. The word pterygium comes from the Greek word for wing, referring to the wing-like folds of tissue often seen.