Active proliferation of telangiectases in skin of patients with progressive systemic sclerosis (PSS).

The labeling index of endothelial cells as measured by in vitro autoradiography with 3H-thymidine and the electron microscopic structure of microvessels were studied in telangiectases. The telangiectases of eight patients with progressive systemic sclerosis (PSS) were compared with the cherry angiomas of six healthy controls subjects. The ultrastructural features of telangiectases were similar in the two groups and were characteristic of capillaries and postcapillary venules of the dermis, with multilayering of the vascular basement membrane. However, a significant difference existed between these two groups in an autoradiographic study: in PSS telangiectases, the average labeling index was 5.9%, whereas in cherry angiomas it was around 0.8%. Thus, the telangiectases in PSS are structures with accelerated endothelial proliferation, as are the other endothelial cells of microvessels anywhere in dermis in this disease. However, the great heterogeneity of the labeling index (varying from 0.5% to 27%) must be emphasized in telangiectases.