A 41-years-old female, with ulcerative colitis, presented to the emergency department with 7-days history of abdominal pain, bloody stools (> 10/day). The patient referred the appearance of a cutaneous lesion, on her left thigh, with subsequent appearance of similar lesions on the lower limbs. No improvement after amoxicillin/clavulanic acid. On admission, she was febrile (38.2 ºC) and tachycardic. She had three cutaneous lesions, the largest one with 8cm in the left thigh - a deep and painful lesion, with extensive ulceration, necrosis, exudative edges and with marked pathergia, compatible with pyoderma gangrenosum.