Abstract
A 53-year-old man presented with painless, bluish discoloration of his fingernails. The thumbs had more distinguished discoloration than his other fingers (Panels A and B). He denied discoloration of his skin, eyes, or teeth as well as cardiovascular, pulmonary, hematologic, or rheumatologic complaints. He had not ingested or had any contact with heavy metals including silver or gold. Medical history was significant for rosacea (>10 years duration), which was well controlled with minocycline (100 mg twice daily). On physical examination bluish-gray discoloration of the lunula of each finger was evident, involving both hands. The capillary refill time, pulse examination, and Allen’s test of each hand was normal. No sclerodactyly, splinter hemorrhages or vascular lesions were noted. Normal Doppler signals were triphasic at the deep palmar arch and each digital artery. Pulse oximetry was normal on room air. Clinically, the patient did not have cyanosis; consequently, the discoloration was consistent with hyperpigmentation. In the absence of exposure to heavy metals, antimalarials, phenothiazines, or amiodarone, a diagnosis of minocycline-induced hyperpigmentation (MIH) was made.
Skin pigmentation is the most common manifestation of MIH and requires a prolonged duration of ingestion (>8 months) with a cumulative dose of >70 g, benchmarks our patient far exceeded. 1 Isolated nail pigmentation is a very uncommon side effect. 2 Typically, MIH affects areas of acne scarring (type I), skin of the anterior shins (type II) or sun-exposed areas (type III). The hyperpigmentation results from minocycline degradation products deposited in macrophages. Minocycline is a water soluble, synthetic tetracycline antibiotic. It has the longest half-life and broadest spectrum of the tetracyclines that predisposes to increased tissue levels with time. 3
Minocycline should be discontinued since other treatment options are available for rosacea.1–3 It is speculated that his nail bed discoloration will resolve with time; however, his prolonged exposure may impact the reversibility.
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Footnotes
Declaration of conflicting interests
The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The authors received no financial support for the research, authorship, and/or publication of this article.