Metastatic Crohn's disease: an underestimated entity.

Cutaneous metastatic Crohn's disease (MCD) is a rare but challenging dermatologic manifestation of Crohn's disease. It is histologically defined as the presence of non-caseating granulomas at skin sites separated from and non-contiguous to the gastrointestinal tract. Cutaneous metastatic Crohn's disease should be distinguished from the much more frequent contiguous cutaneous manifestations of Crohn's disease that present at perianal or, less common, peristomal sites with direct extension from the intestine to the adjacent skin. Versatile clinical presentation and the fact that occurrence can predate the initial diagnosis of Crohn's disease may lead to misdiagnosis, delayed treatment and underreporting. As case numbers are small and randomized controlled studies on management are lacking, the therapeutic approach remains challenging and is often unsatisfactory. We here performed a systematic literature search identifying 264 published pediatric and adult cases of MCD and additionally report three of our own cases. Our review summarizes clinical characteristics, putative etiopathology, histologic findings, differential diagnoses and treatment options for MCD.