Dermatologic manifestations of colonic disorders

Purpose of review The skin is often a mirror for matters of internal diseases including disorders of the gastrointestinal tract. Here we enumerate many cutaneous and gastrointestinal associations and focus closely on three of the lesser known cutaneous manifestations of colonic disorders. Recent findings Muir-Torre syndrome involves cutaneous sebaceous adenomas and internal malignancy; screening of cutaneous lesions for microsatellite instability, and absence of mismatch repair genes provides an opportunity for diagnosis of the syndrome. Degos' disease is a vasoocclusive disorder involving the cutaneous and gastrointestinal systems; this disease affects all ages with significant mortality, yet a benign variant only affecting the skin is described. Anecdotally reported treatments are listed. Metastatic Crohn's disease is the development of noncaseating granulomas at skin sites not contiguous with the gastrointestinal tract; cutaneous lesions may precede the onset of colonic disease or appear in the absence of active bowel disease, and extensive surgical debridement of perineal lesions is often necessary. Summary Knowledge of these cutaneous manifestations provides an insight into the state of colonic health. These clues alert the clinician to the potential for life-threatening consequences, which leads to vigilant screening and hopefully earlier diagnosis.