Two young males with acne fulminans (AF) are described. In addition to severe skin lesions, they had musculoskeletal symptoms including bacteriologically negative osteolytic lesions in the clavicles. Both patients received antibiotics for suspected septic infections. The response was unsatisfactory in both patients, and combination treatment with prednisolone was started. A favourable response was observed, and a relapse occurring in the first patient was controlled by steroids alone. The possible pathomechanism of bone lesions in AF is discussed.