Hyperpigmentation associated with oral minocycline.

Two patient receiving minocycline developed blue-black pigmentation on the legs. Biopsies from the pigmented areas demonstrated granules containing iron, a pigment with staining properties similar to melanin, and a third pigment which may be a degradation product of minocycline. Electron microscopy showed that some, but not all the granules were membrane-bound and they were situated mainly within macrophages. Analytical electron microscopy showed that the granules contained iron, sulphur, chlorine and, in one case, calcium.