Ultrastructure of vascular changes in cutaneous manifestations of Behçet's disease.

We observed small dermal blood vessels embolized by thrombus at the sites of needle-prick reaction as well as erythema nodosum-like lesions in 4 patients with Behçet's disease, by means of electron microscopy. The ultrastructural finding associated with overproductive proliferation of the endothelial cells leading to obliteration of the vascular lumen was the sporadical appearance of degenerated cells among proliferating endothelial cells in both cutaneous manifestations. These degenerated cells showed contraction changes and may be involved in thrombogenesis.