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Is the black thyroid really an innocuous pathological finding?
M C Nollevaux1, M Burlet, J P Squifflet
1Départements d'Anatomie Pathologique, Cliniques Universitaires Saint-Luc, Université Catholique de Louvain, Bruxelles, Belgique.
Insights
Minocycline, an antibiotic used for acne, can cause black thyroid discoloration and potential antithyroid effects. Long-term users should have their thyroid function monitored.
Area of Science:
- Endocrinology
- Pathology
- Pharmacology
Background:
- Thyroid nodules require investigation, sometimes leading to surgical intervention.
- Minocycline is a commonly prescribed antibiotic for acne vulgaris.
- Long-term antibiotic use can have unforeseen side effects.
Observation:
- A 24-year-old woman presented with a cold thyroid nodule.
- Thyroidectomy revealed a diffusely black-colored specimen.
- Microscopic examination showed brown granules and intralysosomal lipofuscin-like deposits.
Findings:
- The observed pathological changes are consistent with "black thyroid".
- These findings are associated with minocycline intake.
- The patient had a history of three years of minocycline treatment for acne.
Implications:
- Minocycline may induce thyroid pigmentation and potentially affect thyroid function.
- Monitoring thyroid tests in patients on long-term minocycline therapy is recommended.
- This case highlights a rare but notable side effect of minocycline treatment.
Abstract:
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.