Acne fulminans, which is the most severe form of acne, affects mainly teenage men; its pathogenesis is unknown. In its most severe form bone lesions may occur, and although they appear to be transient, they cause considerable discomfort to the patient. Roentgen-ologically these lesions are not well defined, and often biopsies are performed to rule out malignancy or infection. The result of bone biopsies has, however, always been reported to be benign, as they are in this case. We report a case of acne fulminans with a distinct presentation of bone lesion in a technetium 99 scan and findings of high levels of C3 and C4 and low levels of serum estradiol. These changes have not been described before and are contrary to previously published findings.