Beyond skin deep: thoracic manifestations of systemic disorders affecting the skin.

A variety of systemic disorders--infections, noninfectious inflammatory diseases, collagen vascular diseases, hereditary diseases, and acquired immune deficiency diseases--may affect both the skin and the lung. The findings in one organ system can help establish the diagnosis or limit the differential diagnosis. Cutaneous manifestations of many conditions (eg, Kaposi sarcoma) precede thoracic manifestations and sometimes have prognostic implications for respiratory disease; in other conditions (eg, organizing pneumonia in polymyositis and dermatomyositis), thoracic manifestations precede cutaneous ones. When skin and thoracic manifestations develop simultaneously, as occurs in the acute form of sarcoidosis known as Löfgren syndrome, the diagnosis is often readily established. Familiarity with the appearances of skin lesions that are commonly associated with systemic lung disease, especially those that are disease specific, may allow the radiologist to pinpoint a diagnosis even when thoracic imaging findings are nonspecific.