Histopathological study of six types of adverse cutaneous drug reactions using granulysin expression

Background Few studies have been published on the histopathology of cutaneous adverse drug reactions (CADR), and most of these lack information on skin allergological tests. The histopathology of drug reaction with eosinophilia and systemic symptoms (DRESS) is also seldom described. The purpose of our study was to examine six types of well- documented CADR (maculopapular exanthema, DRESS, fixed drug eruption, Stevens- Johnson syndrome, toxic epidermal necrolysis [TEN], and acute generalized exanthematous pustulosis) using histopathology and immunohistochemistry to evaluate the expression of granulysin, a key molecule in TEN. Methods We retrospectively included 106 skin biopsies performed in proven cases of CADR (by chronological investigation, single attributable drug, or/and skin tests). All slides were reviewed, and microscopic changes were analyzed using a standardized form. Granulysin expression was studied by immunohistochemistry. Results In DRESS, we observed spongiosis, edema, and basal vacuolization, with rare necrotic keratinocytes and constant lymphocytic infiltrate in the superficial dermis. Eosinophils were often present, and pustules were found in 15% of cases. Necrotic keratinocytes are often absent in maculopapular exanthema. Granulysin was expressed in six types of CADR with a trend toward more intense expression in DRESS and TEN. Conclusion We detailed further about the histopathology of DRESS. Granulysin expression was observed in all CADR with a marked overlap of expression pattern between the six types.