Distinguishing between erythema multiforme major and Stevens-Johnson syndrome/toxic epidermal necrolysis immunopathologically

The early clinical presentations of Stevens–Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are similar to that of erythema multiforme major (EMM). Cytotoxic molecules, especially granulysin, are expressed in the skin lesions of SJS/TEN and cause extensive keratinocyte death. It is postulated that the function of regulatory T cells (Treg) in SJS/TEN is inadequate. This study examined whether an immunohistological examination of cytotoxic molecules and the immunophenotype of Treg is useful for discriminating SJS from EMM in the early period. Over the past 9 years, the lesional skin of 14 patients with SJS/TEN and 16 patients with EMM was biopsied. Double immunofluorescence labeling of CD8 and granulysin, perforin, or granzyme B was performed, and immunohistochemical analyses of granulysin, perforin, granzyme B, CD1a, CD3, CD4, CD8, CD68 and Foxp3 were conducted using a highly sensitive indirect immunoperoxidase technique. The number of cells positive for each antibody per five high‐power fields was counted. The proportions of granulysin⁺ cells/CD8⁺ cells (P = 0.012) and perforin⁺ cells/CD8⁺ cells (P = 0.037) in SJS/TEN were significantly higher than in EMM. The number of Foxp3⁺ cells/five high‐power fields in SJS/TEN was significantly lower than in EMM (P = 0.004). Similarly, the number of CD4⁺ cells/five high‐power fields in SJS/TEN was significantly lower than in EMM (P = 0.0017). These data suggest that these panels of antibodies for labeling cytotoxic molecules, CD4 and Treg are useful for discriminating early SJS/TEN and EMM with a skin biopsy.