Background:Pyoderma gangraenosum is an immune-mediated, inflammatory, neutrophilic dermatosis of unknown etiology, which represents one of the extraintestinal manifestations of inflammatory bowel disease. It is a rare disease that occurs in less than 1% of patients with inflammatory bowel disease and with the same ratio in patients with Crohn's disease and ulcerative colitis.Main observations:A 36-year-old woman was diagnosed with ulcerative colitis 6 years before admission to our dermatology department with an acute disseminated pyoderma gangraenosum with mucosal involvement, during a flare of ulcerative colitis. Disease progression was interrupted by intravenous administration of the tumor necrosis factor-α inhibitor infliximab at 5 mg/kg at weeks 0, 2, and 6 (1st cycle) and every 8 weeks thereafter. Improvement of intestinal, skin and oral manifestations was evident already after the 1st cycle of treatment and has been maintained since (at least 16 months).Conclusions:This case report is one of very few on disseminated pyoderma gangraenosum with oral involvement complicating ulcerative colitis, where infliximab was shown to have a rapid efficacy on skin, mucosal and bowel symptoms.