The pathogenesis of vascular changes in erythema nodosum-like lesions of Behçet's syndrome: an electron microscopic study.

The probable sequence of microvascular changes affecting endothelial cells in erythema nodosum-like lesions was examined by electron microscopy in 18 patients with typical Behçet's syndrome. Dark endothelial cells in the superficial and deep dermis exhibited degeneration with contraction changes. Consequently, degenerated endothelial cells showed nuclear and cytoplasmic condensation, vacuolization in the cytoplasm, and rich ribosomes. Moreover, blood vessels which were enveloped by cuffs of lymphocytes simultaneously exhibited both endothelial cell hypertrophy and endothelial cell necrosis. The implied associations between perivascular lymphocytic cuffs and blood vessels exhibiting endothelial cell alterations indicate that microvascular changes in erythema nodosum-like lesions may be closely associated with the delayed-type hypersensitivity reaction.