Mast cells in leprosy skin lesions.

The variability of mast cell density within and between leprosy skin lesions was examined as a basis for future studies, and whether the number of mast cells in the lesion was determined by local or systemic factors was evaluated. The mast cell density in the granuloma, skin appendages, and intervening dermis was assessed by counting mast cells in glycol methacylate sections stained with Giemsa stain and relating these counts to area measurements obtained by planimetry. In biopsy specimens taken from the edge of established lesions the density of mast cells within the granulomata was considerably higher than that in the intervening dermis and was comparable with that found in the appendages. No major differences in mast cell density were found between unaffected skin and the centre or edge of individual lesions. Mast cell densities in biopsy specimens from the edge of different lesions on the same patient were also similar, suggesting that the mast cell density within the granulomata is independent of the site of the lesion and is determined systemically.