We report a case of pyostomatitis vegetans associated with ulcerative colitis. The patient was a 25-year-old woman referred to our hospital because of irritative pain of the right side of the buccal mucosa. She had been receiving mesalazine for ulcerative colitis for 4 years. An erosion with a cobblestone appearance and a small ulcer were observed on the right side of the buccal mucosa. Histopathological examination showed subepithelial microabscesses containing lymphocytes and eosinophils in the subepithelial connective tissue. We finally diagnosed pyostomatitis vegetans associated with ulcerative colitis. The oral lesion completely disappeared 1 month after the administration of prednisolone.
