Black bones following long-term minocycline treatment

During a surgical procedure, black vertebrae were observed in a 42-year-old white woman. An undecalcified iliac crest bone biopsy specimen revealed intense fluorescence compatible with tetracycline labeling and osteoporosis. A urinary screening test was negative for amino acids. The patient had been treated with minocycline hydrochloride (100 to 300 mg/d) for at least 6 years. Since minocycline is known to discolor many body tissues, it is likely that the black discoloration of bone in our patient was caused by the long-term intake of the antibiotic.