The evolution of lesions in erythema elevatum diutinum.

We obtained biopsies from early, fully developed, and late lesions of erythema elevatum diutinum (EED) in a 49-year-old man. The histologic and electron-microscopic findings were compared with those reported in the literature and three other cases from our files. Early lesions show leukocytoclastic vasculitis with capillary proliferation. Later lesions show vasculitis, dermal aggregates of neutrophils, fibrosis, and areas of granulation tissue. Newly formed vessels in granulation tissue may be more susceptible to damage by immune complexes, and the early formation of granulation tissue in EED may prevent an early resolution of vasculitis. Damage to dermal connective tissue in EED incites either scarring or, rarely, a fibrohistiocytic proliferation. Ultrastructural examination of one case showed histiocytes with myelin figures and intracellular lipid and cholesterol.