We describe a case of a male teenager, affected by acne fulminans. He had lytic bone lesions in both clavicles and arthritis of the right sacroiliac joint and spine. A bone scan showed increased uptake in these areas. Infection or a neoplastic disease was suspected but the cytological examination and the bacterial cultures of the material collected with a fine needle biopsy from the clavicular lesion were negative. The patient was treated with diclofenac and promptly recovered. Our report emphasizes that, although unusual, acne fulminans can be complicated by an erosive systemic arthritis and bone lesions. An immunological mechanism seems to be involved in this association.