TNF and inflammatory bowel disease: Inflammatory bowel disease (IBD) is characterized by aggressive, cytokine-driven, non-infectious inflammation of the gut, caused by T-cells and antigen presenting cells producing pro-inflammatory cytokines (IL-6, Tumor Necrosis Factor-α), which cause mucosal inflammation and destruction.47,105 Cutaneous symptoms in IBD occur with an incidence of up to 40% and the most common are erythema nodosum and pyoderma gangrenosum.106,107