Critical factors differentiating erythema multiforme majus from Stevens-Johnson syndrome (SJS)/toxic epidermal necrolysis (TEN).

Erythema multiforme majus (EMM) and Stevens-Johnson syndrome (SJS)/toxic epidermal necrolysis (TEN) are severe cutaneous reactions characterised by targetoid erythematous lesions and mucocutaneous involvement. The initial skin manifestations are similar, making early diagnosis difficult. We retrospectively reviewed 36 cases of EMM and 18 cases of SJS/TEN and also evaluated 6 patients with unclassified EMM. 13 patients in the EMM group and 16 patients in the SJS/TEN group presented with a high fever (>38.5̊C; p<0.001). Two or more mucous membranes were affected in 6 patients in the EMM group and 18 patients in the SJS/TEN group. Significantly more SJS/TEN than EMM patients had high levels of C-reactive protein and severe hepatic dysfunction. Thirteen EMM and 13 SJS/TEN cases were caused by medications/drugs. Skin biopsy samples showed stronger mononuclear cell infiltration in the EMM than in the SJS/TEN group (p<0.001). The mean dose of initial systemic corticosteroid used to treat EMM was lower than that used to treat SJS/TEN. No patients died in either group. Clinically, the unclassified cases mostly behaved like EMM. The results of our investigation suggest that EMM and SJS/TEN are distinct conditions and they help in differentiating these syndromes at an early stage.