title: A new type of minocycline-induced cutaneous hyperpigmentation.
abstract: Pigmentary disorders are recognized adverse effects of the semi-synthetic tetracycline derivative antibiotic, minocycline. Three distinct types of minocycline-induced cutaneous pigmentation have been described. Type I, blue-black pigmentation confined to sites of scarring or inflammation on the face; Type II, blue-grey circumscribed pigmentation of normal skin of the lower legs and forearms; and Type III, diffuse muddy brown pigmentation of normal skin accentuated in sun-exposed areas. We report two patients with acne vulgaris with a fourth type of minocycline-induced cutaneous pigmentation. They presented with circumscribed blue-grey pigmentation within acne scars confined to the back. Histology showed pigment within dendritic cells, and extracellularly throughout the dermis. Histochemistry identified a calcium containing melanin-like substance. Iron was absent. Immunohistochemistry confirmed some pigment-containing cells to be macrophages. Electron microscopy demonstrated electron-dense granules, free and membrane-bound, within macrophages and fibroblast-like cells. Energy-dispersive X-ray analysis confirmed the presence of calcium. Iron was absent. This fourth type of cutaneous minocycline hyperpigmentation may be a variant of Type I, but based on clinical, pathological and microanalytical differences, appears to be a new entity. The pigment may be a drug metabolite-protein complex chelated with calcium, or an insoluble minocycline-melanin complex. We propose a classification of cutaneous minocycline pigmentation based on clinico-pathological criteria.
authors.affiliation: Department of Dermatology, Faculty of Health Sciences, University of Stellenbosch and Tygerberg Hospital, PO Box 19063, Tygerberg 7505, South Africa. robert.mouton@mailbox.co.za
authors.forename: R W
authors.initials: RW
authors.lastname: Mouton
authors.forename: H F
authors.initials: HF
authors.lastname: Jordaan
authors.forename: J W
authors.initials: JW
authors.lastname: Schneider
mesh_terms: D000152:Acne Vulgaris / Q000188:drug therapy*; D000328:Adult; D000900:Anti-Bacterial Agents / Q000009:adverse effects*; D001706:Biopsy / Q000379:methods; D006801:Humans; D017495:Hyperpigmentation / Q000139:chemically induced* / Q000473:pathology; D008297:Male; D008911:Minocycline / Q000009:adverse effects*; D012867:Skin / Q000473:pathology*
chemical_list: D000900:Anti-Bacterial Agents; D008911:Minocycline