BACKGROUND - Melasma is a common hypermelanosis characterized by symmetric brownish macules on photoexposed areas, most frequently on the face of women. Its pathophysiology is still unknown. OBJECTIVES - To morphologically and functionally characterize and compare melanocytes of normal skin and of melasma. METHODS - Twelve patients with facial melasma were assessed and biopsies of lesions and adjacent healthy skin were performed. The slices were stained with hematoxylin-eosin and Fontana-Masson, immunohistochemically marked for Melan-A and evaluated by electronic microscopy. Quantification of epidermal melanin and melanocytes was estimated by digital cytomorphometric analysis. RESULTS - All patients were female, mean age of 41.3±2.8 years. The Fontana-Masson staining showed an important increase in epidermal melanin as compared to normal skin. The Melan-A staining demonstrated larger and intensely marked melanocytes and more prominent dendrites in the damaged skin. Greater epidermal melanin density was observed in melasma lesions and the digital analysis of number of epidermal melanocytes did not show a significant difference between damaged and normal skin. Electronic microscopy analysis revealed an increased number of mature melanosomes in keratinocytes and melanocytes, with marked cytoplasmic organelles in melasma skin. CONCLUSIONS - Melanogenesis is increased on melasma epidermis as compared to adjacent normal skin.
Immunohistochemistry; Melanocytes; Melanosis; Melanosomes; Microscopy, electron
