Ultrastructure of muscle microvasculature in progressive systemic sclerosis: relation to clinical weakness.

Capillary basement membrane (BM) abnormalities are known to be a feature of the muscle pathology of progressive systemic sclerosis (PSS), but the relation of such an abnormality to clinical disease is uncertain. We have analyzed the muscle microvasculature of 28 patients with PSS, and compared them to both normal controls and to patients with other rheumatic diseases. Our data show that the PSS group as a whole have significantly greater numbers of abnormal capillaries as compared to controls (p less than 0.005), and that the PSS patients with clinical muscle weakness have even more severe and frequent abnormalities (p less than 0.001).