An 84-year-old woman presented to an infectious disease clinic with hyperpigmented grey patches distributed symmetrically along her cheeks, chin and neck (Figure 1). The pigmentation had progressed in colour over 7 months. For the preceding 4 years, the patient had been receiving suppressive oral minocycline therapy (100 mg twice daily) for a prosthetic knee infection. We diagnosed minocycline-induced skin hyperpigmentation. The minocycline was stopped, and therapy with doxycycline was initiated. The hyperpigmentation began to fade over the following 3 months (Figure 2).
Minocycline is a tetracycline antibiotic. It has been used as a treatment for acne vulgaris and rosacea, although current Canadian guidelines do not recommend minocycline as a first-line drug for this indication.1 Hyperpigmentation of the skin, gingiva, teeth, bones, eyes, thyroid gland and other viscera has long been recognized as a potential side effect of long-term minocycline use, with an incidence of 3%–15%.1 There are 4 distinct types of skin pigmentation described in the literature.2–4 Type I minocycline-induced hyperpigmentation presents as blue-black macules at the site of previous inflammation and scarring, resulting from deposition of pigmented granules in the dermis.2,3 Patients with type II minocycline-induced hyperpigmentation develop blue-grey discolouration on healthy skin of the extremities, most often the shins. This occurs owing to deposition of minocycline metabolites in the skin.2,3 Type III minocycline-induced hyperpigmentation presents as a muddy-brown discolouration in sun-exposed areas and may result from increased melanization of the skin basal cell layer.2,3 Type IV minocycline-induced hyperpigmentation has the same cause as type III and involves preexisting scars.4 Based on the distribution of the hyperpigmented patches, our patient had type III minocycline-induced hyperpigmentation. A cumulative minocycline dosage of at least 70–100 g appears to be important in the development of types II and III hyperpigmentation, whereas the relation of type I hyperpigmentation to total dosage is less clear.2 Management consists of discontinuing the antimicrobial or the use of Q-switched lasers, although skin changes may persist, particularly with type III hyperpigmentation.2,3 Patients taking long-term courses of minocycline should be alerted to the risk of hyperpigmentation.
Acknowledgements
The authors thank Dr. Shane Silver, Section of Dermatology, Department of Medicine, University of Manitoba, for his careful review and helpful comments.
Footnotes
Competing interests: None declared.
This article has been peer reviewed.
The authors have obtained patient consent.