cqvip:An adverse cutaneous reaction to a systemically administered drug may rarely manifest as acute generalized exanthematous pustulosis (AGEP). Several recent reports have documented positive patch test results in patients with a history of AGEP, while two have demonstrated drug- specific in vitro lymphocyte proliferative responses. These findings suggest that drug- specific T cells mediate AGEP. We describe two patients with a history of AGEP who each demonstrated positive patch test results specific for the inciting drug: Patient # 1 to the antibiotic metronidazole, and Patient # 2 to the calcium channel- blocker diltiazem. Histologic examination of biopsy specimens taken from the patch test sites of these patients revealed spongiotic dermatitis and perivascular lymphocytes consistent with a delayed- type hypersensitivity reaction, rather than demonstrating subcorneal neutrophilic pustules more typical of AGEP. In vitro testing by measuring peripheral T cell proliferative responses to chemically purified drug correlated with the clinical response. In a direct cross- comparison, patch test results were shown to correlate with in vitro lymphocyte proliferative responses in two patients with a history of AGEP to different drugs. These findings provide additional evidence that the pathogenesis of AGEP involves a T cell- mediated immune response.
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