Drug-induced exanthems.

Cutaneous adverse reactions to drugs can comprise a broad spectrum of clinical and histopathological features. Recent evidence from immunohistological and functional studies of drug-reactive T cells suggest that distinct T-cell functions may be responsible for this broad spectrum of different clinical reactions. Maculopapular exanthems represent the most commonly encountered cutaneous drug eruption. Previous studies on maculopapular exanthems indicate that drug-specific CD4+ T cells expressing cytotoxic granule proteins such as perforin and granzyme B are critically involved in killing activated keratinocytes. These cells are particularly found at the dermo-epidermal junction and may contribute to the generation of vacuolar alteration and destruction of basal keratinocytes, which are typical found in drug-induced maculopapular exanthems. In contrast to maculopapular exanthems, the preferential activation of drug-specific cytotoxic CD8+ T cells may lead to more severe reactions like bullous drug eruptions. Furthermore, activation of drug-specific T with distinct cytokine and chemokines profiles may also explain the different clinical features of drug-induced exanthems. IL-5 and eotaxin are upregulated in maculopapular exanthems and explain the eosinophilia often found in these reactions.