Is the black thyroid really an innocuous pathological finding?

We report the case of a 24-year-old euthyroid woman in whom the discovery of a cold nodule in the left thyroid lobe led to a thyroidectomy. The surgical specimen was characterized by a diffuse black discoloration. Optical examination revealed brown granules within the apical portion of the follicular cells whereas ultrastructural studies showed intralysosomal lipofuscin-like deposits, all findings consistent with pathological descriptions reported in black thyroids associated with the intake of minocycline. Retrospectively, we were told that the patient had received this antibiotic for at least three years for the treatment of acne vulgaris. As experimental models have demonstrated potential antithyroid effects of the drug, it appears relevant to monitor thyroid tests in patients receiving long-term minocycline therapy.