[Bullous drug reactions]

Bullous drug exanthems are clinically characteristic, usually severe cutaneous and mucosal drug hypersensitivity reactions. Commonly, they appear 5-14 days after onset of drug treatment. Therapy of choice is to avoid the culprit drug and systemic administration of glucocorticoids. A key element in the immune pathogenesis of bullous drug exanthems is presumably the activation of cytotoxic CD8(+) T lymphocytes which recognize drug metabolites as nominal antigens. These compounds form spontaneously (e.g. penicillins) or are metabolized by cytochrome P450-dependent enzymes (sulfonamides). The diagnosis of bullous drug exanthems is primarily based on skin tests and in vitro-techniques. Among the skin tests, prick as well as patch tests are important. Patch tests can be also applied at the former skin lesion in fixed drug eruption. In vitro techniques include analysis of drug-specific IgE (only available for anti-penicillin, anti-sulfamethoxazole) and cellular tests with the patients' lymphocytes (lymphocyte transformation test-LTT).