Patterns of regeneration in vessels of human diseased muscle and skin. An ultrastructural study.

Regenerating vessels from 36 muscle biopsies and 12 skin biopsies pertaining to patients with the clinical and histological diagnosis of dermatomyositis-polymyositis and other inflammatory myopathies were described ultrastructurally. The following characteristics of vascular regeneration were encountered: a) alternation of thin and thick endothelial cells, b) superimposed segments of endothelial cytoplasm with formation of twisted intercellular junctions, c) long and complex intraluminal endothelial projections, d) discontinuous and porous perivascular basement lamina or multilaminated basement lamina. Some vessels featured only two or three of the mentioned characteristics. Endothelial fenestrations were occasionally encountered in the skin capillaries and were an exception in the muscle capillaries. In the skin there were aspects suggesting that intercalation of perivascular cells in the regenerating endothelial wall may occur. Most capillaries were in the final stage of regeneration.