Four cases of minocycline-induced hyperpigmentation of the tongue

Minocycline is a semi-synthetic, broad-spectrum, antimicrobial agent that was first introduced into clinical practice in 1967. Its primary indication is for the treatment of acne vulgaris, where its success has been attributed to a combination of its bacteriostatic and anti-inflammatory activities. There has been recent interest in minocycline use in the treatment of various other chronic inflammatory and immune-mediated diseases such as Behçet's disease and recurrent apthous ulceration. A well-recognized side effect of minocycline treatment is pigmentation, which has been reported in multiple tissues including skin, nail beds, sciera, bone, the thyroid, and teeth. However, pigmentation of the tongue caused by minocycline is very rare. We report four cases of actual pigmented lesions on the tongue and finger nails due to minocycline therapy, followed by a discussion of minocycline-induced hyperpigmentation.