"Black thyroid" associated with minocycline therapy. A report of an autopsy case and review of the literature.

An autopsy case of a 69-year-old woman showing black discoloration of the thyroid gland designated as "Black thyroid" was reported. The patient received long-term, high dose antibiotics minocycline therapy (total dose: 70 g) for bronchial asthma associated with respiratory infection and died of uterine cancer. The thyroid gland was coal black in color and histological examination revealed numerous dark brown pigments scattered in the follicular epithelium and colloid matrix. Special stains and electron microscopic examination suggested these deposited pigments to be consistent with lipofuscin. Histological examination of the thyroid glands in consecutive 500 autopsy cases revealed intimate relationship between deposition of lipofuscin pigments in the follicular epithelium and age of the patients. But, massive deposition of lipofuscin in the thyroid alone did not make the thyroid black and addition of minocycline appeared to be necessary for the black discoloration.