[Cutaneous pigmentation induced by minocycline: ultrastructural analysis and X-ray microanalysis]

The authors report a case of cutaneous pigmentation induced by minocycline. The patient (aged 59) presented with a bluish-grey pigmentation on her face, legs and nails. She had been receiving minocycline for 8 years for asthma. The cumulative dose was 400 g. Skin biopsy specimens from the pigmented areas were examined by light and electron microscopy. Light microscopy displayed hyperpigmentation with Fontana's stain in the dermis, macrophages and basal layer of the epidermis. Electron microscopy showed an increase in melanosomes within the basal keratinocytes, and dense granules in macrophages of the dermis. An X-ray microanalysis of the electron-dense granules showed the presence of larger quantities of iron and smaller quantities of sulphur and calcium. The different types of pigmentation are reviewed. Several pigments are thought to be responsible for the pigmentation but the underlying mechanism remains unclear.