DISORDERS OF PIGMENTATION
Vitiligo causes irregular, completely depigmented skin patches. It is common andcan affect any race; there may also be a familial predisposition. The disease has an unknown etiology that is possibly autoimmune. Microscopically, affected areas are devoid of epidermal melanocytes.
Melasma causes irregular blotchy patches of hyperpigmentation on the face; it isassociated with sun exposure, oral contraceptive use, and pregnancy (“mask of preg-nancy”) and may regress after pregnancy.
Freckles (ephelides) are light brown macules on the face, shoulders, and chest. Theyare common in fair-skinned children and tend to darken and fade with the seasons due to sunlight exposure. Microscopically, freckles are characterized by increased melanin deposition in the basal cell layer of the epidermis with a normal number of melanocytes.
Benign lentigo is a localized proliferation of melanocytes which cause small, oval, light brown macules. Microscopically, benign lentigos show linear melanocytic hyperplasia.