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Notes: Summary The clinical and histopathological classification of erythema exudativum multiforme major (EEMM), Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are difficult, due to the lack of clear-cut criteria. Based on a new clinical classification, 149 of 219 (68%) histopathological specimens, from a total of 534 patients with EEMM. SJS and TEN, have been reviewed. A comparison was made with the clinical picture, and any past history of infection or drug intake. All patients had been included in the German Registry of Severe Skin Reactions between April 1990 and December 1993. No differences could be found between the biopsies examined and the total number of histopathological specimens, concerning clinical diagnosis, gender and age. Sections from 28 of 149 specimens were not diagnostic or were too old to be properly evaluated. In nine cases, other diagnoses were proposed. One hundred and eleven of the histological slides with the diagnosis of EEMM (n= 16), SJS (n=34) and TEN (n=61), were classified as epidermal type of erythema multiforme. In these 111 slides, necrotic keratinocytes could be found, ranging from individual cells to confluent epidermal necrosis. The epidermo-dermal junction showed changes ranging from vacuolar alteration up to subepidermal blisters. The dermal infiltrate was superficial and mostly perivascular. It was sparse in SJS and TEN, and more pronounced in EEMM. Oedema in the papillary dermis was evident occasionally in all clinical groups. In 59 of 111 cases (53%), at least one eosinophil was present in the dermis. In 11 of 111 (10%), more than 10 eosinophils per field could be seen. Eosinophils were less common in the patients with the most severe forms of TEN, in whom there was detachment of more than 30% of the skin surface area. No differences in the history for drug intake, or for infection with Mycoplasma pneumoniae, herpes simplex and other organisms, could be detected between patients with or without eosinophils in their skin sections. This dermatopathological study of patients with EEMM. SJS and TEN indicates that the epidermal type of erythema multiforme is the pathological correlate for these diseases.