Abstract
It is usually difficult to get confirmative diagnosis of drug eruptions using only histopathological findings. In severe drug eruptions, it is sometimes too late to start treatment no matter how immediately the typical histopathological features are detected; consequently, the prognosis is poor. Therefore, early diagnosis and treatment are absolutely necessary. We examined and evaluated the characteristics of the histopathological findings of severe drug eruptions and determined that the interface changes of dermoepidermal junction were the most important findings. In many cases, infiltrates of eosinophils was found in the dermis. When the interface change is severe with obvious cleft formation, accompanied by many necrotic keratinocytes in the epidermis, we must consider Stevens-Johnson syndrome or toxic epidermal necrolysis, and early systemic high-dose steroid therapy is necessary. On the other hand, when the interface change is slight and few necrotic keratinocytes are observed, an erythema multiforme-type drug eruption or drug-induced hypersensitivity syndrome (DIHS) starting from erythema multiforme-like eruption should be considered. Systemic steroid administration at a moderate-dose should be a choice of therapy. When there are many necrotic keratinocytes, however, a high dose of steroid therapy is needed.
