Genetics and the metabolic syndrome.

Originally coined as "syndrome X" in 1988 by Gerald Reaven (1928), the metabolic syndrome (MetS) encompasses a constellation of risk factors, the coincidence of which amounts to an increased cardiovascular and diabetic risk. Rising numbers of dermatoses are being recognized as cutaneous markers of MetS. Dermatologists should look beyond treating the cutaneous condition and quantify the associated increase in cardiovascular risk. The original dermatosis associated with obesity was acanthosis nigricans-described in 1889 by Paul Gerson Unna (1850-1929) and Sigmund Pollitzer (1859-1937). Over the last 20 years, clear associations between psoriasis, hidradenitis suppurativa, and MetS have also emerged. Several studies have shown synergistic improvement in the cutaneous pathology after treatment of components of MetS. This suggests common causalities and is a burgeoning area of research. We review the available evidence about the genetics underlying psoriasis, hidradenitis suppurativa, and acanthosis nigricans. Despite the strong clinical associations, the underlying genetic basis for a link to MetS remains unclear.