Minocycline hydrochloride and thyroid pigmentation. A case report with histological and ultrastructural study

A 20 yr-old male, with a long history of severe acne vulgaris treated with minocycline hydrochloride, died as a result of a motor bike accident. An incidental finding at postmortem was black pigmentation of the thyroid, which was evident histologically as brown-black granules within the cytoplasm of thyroid follicular cells. Ultrastructural examination showed cytoplasmic bodies, of the same type as seen in normal thyroids. Previous cases were reviewed, and the possibility that the pigment is related to lipofuscin discussed.