Drug-Induced Melanosis


A variety of drugs can induce oral mucosal pigmentation.
These pigmentations can be large yet localized, usually to the hard palate, or they can be multifocal, throughout the mouth. In either case, the lesions are flat and without any evidence of nodularity or swelling. The chief drugs implicated are the quinoline, hydroxyquinoline, and amodiaquine antimalarials. These medications have also been used in the treatment of autoimmune diseases. Minocycline, used in the treatment of acne, can also produce oral pigmentation. The pigment is not confined to oral mucosa and is also encountered in the nail bed and on the skin. Last, oral contraceptives and pregnancy are occasionally associated with hyperpigmentation of the facial skin, particularly in the periorbital and perioral regions (Figure 6-7). This condition is referred to as melasma or chloasma. Endocrine disease should be excluded by appropriate laboratory studies when oral or facial nonphysiologic melanosis is encountered.
The cause is unknown, and the pigment may remain for quite some time after withdrawal of the incriminated drug. Microscopically, basilar melanosis without melanocytic proliferation is observed, and melanin incontinence is commonly seen.