Skin capillary changes in early systemic scleroderma. Electron microscopy and "in vitro" autoradiography with tritiated thymidine.

Skin biopsy specimens obtained from involved and noninvolved areas in a patient with early diffuse systemic scleroderma were processed for histology, electron microscopy, and "in vitro" autoradiography with tritiated thymidine. The affected area revealed cellular infiltrates around the eccrine sweat glands, consisting of plasma cells and lymphocytes. The capillaries showed thickening of the basement lamina, damage of endothelial cells, and obstruction of their lumens. However, in some vessels, endothelial cells were preserved and appeared in prophase. Autoradiography with tritiated thymidine showed a marked increase in endothelial and periendothelial cell labeling. Blood immunological studies revealed an increase in B-lymphocytes, IgG, and IgA and the presence of antinuclear and antismooth muscle antibodies.