Diagnosis: Minocycline-induced hyperpigmentation
We referred the patient to a dermatologist, who diagnosed minocycline-induced hyperpigmentation of the skin and sclera.
Minocycline hydrochloride, a derivative of tetracycline, is a broad-spectrum antibiotic that is often used to treat rosacea (which our patient had) and acne vulgaris. Minocycline’s lipid-soluble properties enable penetration into sebaceous glands and subsequent clearing of acne in many cases.1
Despite minocycline’s therapeutic effect, it can lead to a non–dose-dependent pigmentation of the skin (typically a blue-gray pigmentation on the legs), nails, sclera, bones, oral mucosa, teeth, and thyroid.1,2
Rare serious adverse effects include systemic lupus erythematosus (antinuclear antibody positive, DNA antibody negative), pseudotumor cerebri syndrome, and an autoimmune drug reaction leading to hepatitis. Resolution of these conditions occurs slowly once minocycline is discontinued.1 However, scleral hyperpigmentation may be permanent. This pigmentation appears blue-gray.3
Hyperpigmentation falls into 4 categories
Although the etiology of the minocycline-induced hyperpigmentation is unclear, iron and melanin-staining granules identified in dermal dendrocytes and macrophages are likely responsible for producing the blue-gray pigmentation of the skin.2,4
The hyperpigmentation of minocycline is classified into 4 different types, based on clinical features, light and electron microscopy, and energy dispersive X-ray analysis:
Type I is a blue-gray discoloration that appears on the face at sites of inflammation or scarring.
Type II is characterized by blue-gray pigmentation of normal skin of the anterior lower legs.
In Type III, the skin has a muddy brown appearance at sun-exposed sites.2
Type IV occurs in scars, giving them a blue-gray appearance.5