The overlooked surface: cutaneous manifestations of inflammatory bowel disease

Inflammatory bowel disease (IBD) is characterized by a chronic, idiopathic inflammation of the intestinal tract. The primary types include ulcerative colitis (UC), which affects the colon and rectum with continuous mucosal and submucosal lesions solely and Crohn's disease (CD), which may involve any segment of the gastrointestinal tract with discontinuous lesions. Among extraintestinal manifestations (EIMs), the skin is most frequently involved. Erythema nodosum (EN) and pyoderma gangrenosum (PG) are identified as the most prevalent cutaneous presentations. This review explores the underlying mechanisms, clinical features, and treatment options for skin symptoms in IBD, including Sweet's syndrome (SS), metastatic CD (MCD), psoriasis, hidradenitis suppurativa (HS), EN, and PG. Studies show that having one EIM increases the chance of developing others. Biologic drugs have revolutionized IBD treatment but can cause various skin side effects. Although the precise mechanisms linking IBD to these dermatological conditions remain incompletely understood, shared immune pathways and genetic predispositions suggest an association. Factors like genetics, immune system disturbances, changes in gut and skin microbiota, environmental factors, treatments, and epigenetics all play roles. These factors interact through the gut-skin immune link, causing systemic inflammation that can trigger skin issues. Further research is imperative to elucidate the fundamental mechanisms underlying these cutaneous presentations.