Diagnosis: Minocycline-induced hyperpigmentation
The patient’s clinical presentation of chronic blue-black hyperpigmentation on the anterior shins of both legs after a prolonged antibiotic course led us to conclude that this was an adverse effect of minocycline. Commonly, doctors use minocycline to treat acne, rosacea, and rheumatoid arthritis. In this case, it was used to provide chronic antimicrobial suppression.
Not an uncommon reaction for a patient like ours. One small study conducted in an orthopedic patient population found that 54% of patients receiving long-term minocycline suppression developed hyperpigmentation after a mean follow-up of nearly 5 years.1 The hyperpigmentation is solely cosmetic and without known clinical complications, but it can be distressing for patients.
There are 3 types of minocycline-induced hyperpigmentation:
- Type I is a circumscribed blue-black pigmentation that manifests in skin that previously was inflamed or scarred, such as facial acne scars.2 Histopathologic findings include black pigment granules in macrophages and throughout the dermis that stain with Perls Prussian blue iron.3
- Type II (which our patient had) is circumscribed blue-black pigmentation that appears in previously normal skin of the forearms or lower legs—especially the shins.3 On histopathology, black pigment granules are found in the dermis with macrophages that stain with Perls Prussian blue iron and Fontana-Masson.3
- Type III is a diffuse muddy brown hyperpigmentation in previously normal, sun-exposed skin.2 Histopathologic findings include increased melanin in basal keratinocytes and dermal melanophages that stain with Fontana-Masson.3
Types II and III may be related to cumulative dosing, whereas type I can occur at any point during treatment.2
Differential includes pigmentation disorders
The differential diagnosis includes Addison disease, argyria, hemochromatosis, and polycythemia vera, which all can cause diffuse blue-gray patches.4 Brown-violet pigmentation on sun-exposed areas, redness, and itching are more typical of Riehl melanosis.4
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