Cutaneous Crohn's disease after proctocolectomy for medically refractory colonic Crohn's disease: a case series and review of the literature.

Background: Cutaneous Crohn's disease (CCD), also known as metastatic Crohn's disease (CD), is one of the rarest and most challenging cutaneous manifestations of CD. It is characterized by non-caseating granulomatous inflammation of the skin at sites that are non-contiguous with the gastrointestinal (GI) tract. Diagnosis of CCD needs a high clinical suspicion since morphological presentation varies widely and lacks an apparent correlation to the activity of the luminal CD. The onset of CCD in patients without active GI CD is a particularly understudied phenomenon. Methods: We present a case series of a unique patient group who developed CCD while in remission from a luminal CD perspective, mainly after a proctocolectomy for Crohn's colitis. We also provide a literature review and summary of case reports of CCD after proctocolectomy. Results: Our 4 adult patients diagnosed with CCD after proctocolectomy presented herein, were successfully treated with high-dose corticosteroids, followed by biologic therapy. Furthermore, a comprehensive review of CCD is provided regarding its pathogenesis, clinical presentation, differential diagnosis, and the evidence behind the available treatments. Conclusions: CCD should be considered in any CD patient presenting with skin lesions regardless of their disease activity status and history of proctocolectomy. The treatment remains challenging; biologics remain the cornerstone and a multidisciplinary approach is recommended. Larger randomized clinical trials are essential to determine the optimal treatment protocol and to improve outcomes.