Inflammatory bowel disease (IBD) with its two main subtypes Crohn's disease and ulcerative colitis is not restricted to the gastrointestinal tract. Indeed, so-called extraintestinal manifestations (EIMs) are frequent and considerably affect morbidity and mortality. The prevalence of EIMs ranges from 6 to 47%. In up to one quarter of the patients, EIMs can present even before an IBD diagnosis is established. The pathophysiology of EIMs remains elusive, although data from clinical trials demonstrating anti-tumor necrosis factor (TNF) efficacy suggest a common pathogenic link between intestinal and extraintestinal disease activity. However, not all EIMs parallel intestinal disease. Skin lesions are usually classified based on their pathophysiological association with the underlying intestinal disease into four categories: (1) specific, (2) reactive, (3) associated, and (4) treatment-induced manifestations. Cutaneous manifestations include erythema nodosum (EN), pyoderma gangrenosum (PG), Sweet's syndrome, and oral lesions, with EN being the most commonly reported and PG showing the most debilitating disease course. Anti-TNF-induced skin reactions are a new, but increasingly recognized phenomenon, which can be eventually misinterpreted as psoriatic lesions. Medical treatment modalities are limited with topical and systemic steroids being the most frequently employed agents. If EIMs parallel intestinal disease activity, the therapeutic cornerstone usually is the management of underlying intestinal disease activity rather than direct treatment of the EIMs. However, increasing evidence for anti-TNF agents' efficacy in EIM management has changed the approach to complicating and debilitating disease courses. In the case of anti-TNF-induced lesions, topical steroids are usually sufficient and discontinuation of anti-TNF is seldom warranted. In this review, we summarize current knowledge on cutaneous EIMs, their diagnostic criteria and clinical presentation, natural history, pathogenesis, and treatment options.
Keywords: Anti-TNF-induced skin lesions; Erythema nodosum; Extraintestinal manifestations; Inflammatory bowel disease; Pyoderma gangrenosum.