Skin signs of systemic diseases.

The skin should not be considered as an isolated organ but rather as a definite functioning system that communicates with the internal environment. Skin signs of systemic diseases occur frequently and sometimes feature the first symptoms of an internal disease; furthermore, these manifestations may be the sole expressions of otherwise asymptomatic systemic disorders. A number of dermatologic signs, symptoms, and disorders can be invaluable as markers of systemic disease. Although a plethora of specialized modern diagnostic tests are available, the skin still remains the only organ of the body that is immediately and completely accessible to direct clinical examination. This contribution reviews the skin signs of systemic diseases. The description of the clinical features of skin lesions observed in several internal diseases will be useful to general physicians, internists, and dermatologists in the diagnosis of a systemic disease.