Common histopathological processes of phenytoin drug eruption

Fifteen patients (6 males and 9 females) with phenytoin drug eruptions which ultimately resulted in various skin manifestations were analyzed histopathologically. The following types of skin manifestations were noted; 2 cases of toxic epidermal necrolysis, 2 cases of mucocutaneous ocular syndrome, 6 cases of erythema exudative multiform, 3 cases of lichenoid, and 2 cases of the maculopapular type. All of the biopsied specimens from these different skin manifestations exhibited some of the more common histopathological findings: 1) adhesion of the infiltrated cells to the basal layer of the epidermis, 2) cell infiltration into the epidermis, 3) vacuolation of the basal cells, 4) dyskeratotic cells in the epidermis, and epidermal necrosis. Immunohistopathological examinations in 5 typical cases with different skin manifestations revealed that epidermal cells and infiltrating cells were HLA-DR antigen positive. The infiltrating cells in the dermis consisted of almost equal numbers of CD4+ and CD8+ cells; CD8+ cells were predominant in the cells infiltrating into the epidermis. These findings suggest a possibility that the various clinical features in phenytoin drug eruptions may share some common mechanisms.