The histopathology of subcutaneous minocycline pigmentation

Hyperpigmentation associated with prolonged minocycline use is well documented. The histopathology of cutaneous minocycline pigment is characterized by deposition of brown/black, Fontana-Masson, and Perls' positive granules deposited along elastic fibers in the papillary dermis and occurring within macrophages along vessels and eccrine units in the dermis. The subcutis may also be involved; however, the specific subcutaneous findings associated with minocycline hyperpigmentation have not been well established. We present the histopathologic findings of 4 cases of minocycline hyperpigmentation with subcutaneous involvement. Green-gray, flocculent, nonrefractile globules within macrophages were found in the subcutis of all patients. Two of 4 cases exhibited lipomembraneous changes that were also associated with pigment. These distinctive findings may provide additional clues to enable a diagnosis of drug-induced hyperpigmentation to be offered, even in the absence of a clear clinical history.