Comparative Histopathologic Study of Drug Eruption and Rubella

Background : Dermatologists frequently see morbilliform rash in the clinic, drug eruptions and viral eruptions. Due to close clinical similarities, it is difficult to differentiate them. Objective : The purpose of this study was to review the histopathologic differences between drug eruption and viral eruption. Method : In this study, 13 patients diagnosed as rubella and 13 patients diagnosed as drug eruption in Department of Dermatology, Presbyterian Medical Center from 1995 to 1997 were included. We reviewed the epidermal changes such as vacuolopathy, dyskeratotic cells, spongiosis and exocytosis and dermal changes by light microscopy. Results : 1. Vacuolopathy of basal layer was observed in 92.3% of patients in both diseases. 2. Dyskeratotic cells, spongiosis and exocytosis were observed significantly highly in drug eruption. 3. Perivascular lymphohistiocytic infiltration was mild in both diseases, but eosinophilic infiltration was significantly higher in drug eruption(84.6%) than viral eruption(15.4%). 4. Atypical lymphocytes were observed in both diseases. 5. Red blood cell extravasation was observed only in viral eruption. 6. Perivascular edema was significantly higher in drug eruption(76.9%) than viral eruption(38.4%) Conclusion : There was statistically significant differences in dyskeratotic cells, spongiosis, dermal eosinophilic infiltration and Red blood cell extravasation. Considering these observations, histopathologic findings may be helpful in differentiating between drug eruption and viral eruption.