Mast cell changes in a case of rapidly progressive scleroderma-ultrastructural analysis.

A 63-year-old woman had rapidly progressive scleroderma and died 4 months after the clinical appearance of her illness. Extreme itching of the affected skin was prominent. Electron microscopic study of the clinically uninvolved skin showed mainly normal mast cells. Mast cells in clinically involved skin showed a wide morphologic spectrum including evidence of cellular activation. There was an increased amount of cytoplasm occupied by polysomes and mitochondria and less cytoplasm occupied by granules. Most granules were pale and swollen, suggesting active degranulation. In some cases it was difficult to distinguish a hyperactive mast cell with only a few granules remaining from a fibroblast which had acquired granules by transgranulation. This case illustrates the active participation of mast cells in acute scleroderma.