Elevated levels of circulating platelet aggregates and beta-thromboglobulin in scleroderma.

Levels of circulating platelet aggregates and plasma beta-thromboglobulin reflect the degree of platelet activation in vascular injury and repair. Both values were evaluated in 38 patients with scleroderma and 18 control subjects matched for age, sex, and race. Circulating platelet aggregates (expressed as percentage of total platelet count) were 7.2 +/- 5.5% (mean +/- SD) in the control group and 31.2 +/- 13% in the scleroderma group (p less than 0.0005). Beta-thromboglobulin levels in the control groups were 20 +/- 10 ng/mL and 72.7 +/- 50 ng/mL in the group with scleroderma (p less than 0.0005). A positive correlation was found between the two values (r = 0.6, p less than 0.0005). Significant reductions in circulating platelet aggregates and beta-thromboglobulin levels were achieved in 10 patients by dipyridamole and aspirin therapy. These results show in-vivo activation of platelets in scleroderma with release of platelet granule constituents. Antiplatelet therapy in adequate doses returned both values to normal; however, its long-term effect on scleroderma is not yet known.