Erythema elevatum diutinum: clinical, histopathologic, and immunohistochemical characteristics of six patients.

Erythema elevatum diutinum (EED) is a chronic cutaneous vasculitis occurring in association with a variety of conditions including autoimmunity, infectious disease, and hematological abnormalities. The role of associated medical problems is controversial, and the exact pathogenesis of EED is unknown. A series of six cases is reported. The typical clinical presentation was that of erythematous papules and plaques involving the extensor surfaces of the extremities. Histologically, a spectrum from leukocytoclastic vasculitis to vessel occlusion and dermal fibrosis was seen. The lesions of EED have many mimics clinically and histologically. Establishing the diagnosis of EED is important so appropriate screening for associated conditions can ensue. The vascular endothelium of EED stains positive for CD31, CD34, VEGF, and factor VIIIa and negative for factor XIIIa, TGFB, and LANA, a reaction pattern that does not distinguish it from similar appearing lesions. Thus, the chronic and recurrent nature of EED is the primary means of distinguishing it from entities that are clinically and histologically similar.