Erythema-multiforme-like eruption due to topical contactants: expression of adhesion molecules and their ligands and characterization of the infiltrate.

Erythema-multiforme-like reactions are a rare manifestation of allergic contact sensitivity, the pathomechanisms of which and their possible relationship to erythema multiforme remain unclear. We present our histopathological and immunohistochemical findings regarding the expression of several adhesion molecules and immunophenotypic markers of the infiltrate in skin biopsy specimens from 2 cases of erythema-multiforme-like reactions due to contact sensitizers and 3 cases of typical post-herpetic erythema multiforme. The histopathological pattern of erythema-multiforme-like reactions was characterized by an upper-dermal perivascular lymphoid infiltrate with exocytosis and keratinocyte necrosis; in 1 of the cases, there were foci of spongiosis and an admixture of eosinophils in the infiltrate. In comparison with biopsy specimens from cases of typical erythema multiforme, in both cases of erythema-multiforme-like reactions, the epidermal expression of ICAM-1 was more prominent, the % of CD4+ cells in the infiltrate was higher and the % of CD69+ cells was lower. There were no other significant differences in the cell phenotype of the infiltrate or in adhesion molecule expression in biopsy samples from both disorders.