XI International Pigment Cell Conference

Melasma is an acquired dark-brown to ashen-gray hypermelanosis with mottled patterns and is found in the exposed areas (forehead, malar eminences, upper lip, chin, neck, etc.). Although melasma is believed to be associated with pregnancy, including several other factors such as genetic, racial, endocrine, and nutritional, exposure to sunlight appears to be one of the primary causes of its exacerbation. Examination of patients with Wood's light (320-400 nm) is invariably helpful in recognizing the specific type of melasma, and this depends upon the distribution of pigment granules (melanosomes) as epidermal, dermal, or mixed. Histological studies of skin biopsies and sodium bromide-split, Dopa incubated specimens of epidermis obtained from 13 Hispanic patients with melasma (face and unexposed buttock skin) revealed the following: (I) Increased melanization and distribution of melanin in the skin can be detected with Fontana-Masson stain not only in the basal, suprabasal, and granular cell layers but also in the superficial and deep dermis in the form of melanophages. (2) The basement membrane appeared intact, although in at least three biopsies we could discern the discontinuity of the basement membrane zone and vacuolization of the basal cells. (3) Comparison of the biopsies of the melasma skin with unexposed areas after sodium bromide treatment and Dopa incubation revealed a significantly increased population of melanocytes in patients with melasma. These pigment-producing cells exhibited enlarged perikarya and abundant dendritic arborization. The type-specific pigment-producing cells appeared to be engaged in increased formation, melanization, and transfer of pigment granules to the epidermis as well as to the dermis. It would appear that melasma is a circumscribed hypermelanosis primarily of the epidermis with minimal to moderate melaninosis of the superficial and deep dermis.