[A case report of Legionella pneumonia in a patient with ulcerative colitis undergoing remission maintenance using azathioprine].

A 67-year-old man was diagnosed with ulcerative colitis one year ago. Remission was induced via the oral administration of prednisolone and azathioprine;prednisolone was gradually reduced and discontinued. He maintained remission with azathioprine but developed fever and general malaise and visited the Kagawa Prefectural Central Hospital. Chest radiography and a urinary antigen test revealed Legionella pneumonia. His symptoms reduced immediately after the initiation of levofloxacin. Azathioprine suppresses cellular immunity and may increase the risk of Legionella pneumonia.