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Clinical Problem Solving: Pathology
Nov 2012

Pathology Quiz Case 2: Diagnosis

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Arch Otolaryngol Head Neck Surg. 2012;138(11):1094-1095. doi:10.1001/archotol.138.11.1094

Diagnosis: Papillary thyroid carcinoma arising in the setting of black thyroid

Black thyroid is gross black pigmentation of the thyroid gland, most often the result of long-term minocycline therapy.1 Black thyroid was first described in 1967, when the administration of minocycline to rats, dogs, and monkeys resulted in dose-dependent deposits of grossly black pigmentation in the thyroid glands.1 In addition to its effects on the thyroid, minocycline is known to cause blue-black pigmentation of the skin, teeth, nails, and bone, with cutaneous effects being the most commonly observed.2 The use of other tetracycline derivatives can cause similar pigmentation, particularly in the skin and teeth, but aside from minocycline, to our knowledge only the use of doxycycline has been described in a case of black thyroid.3 Classically, black thyroid has been associated with the administration of high doses of minocycline, with most patients using the drug for more than 1 year before being diagnosed as having black thyroid. However, shorter durations have also been observed, with 1 study relating black thyroid to a 12-day course of doxycycline.25 Reversal of pigmentation on cessation of minocycline therapy appears to be unlikely,2,4,5 although cutaneous pigmentation has been known to reverse in months.2

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