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.
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