[The use of skin testing in the investigation of toxidermia: from pathophysiology to the results of skin testing].
Drug skin tests can be of value in investigating cutaneous adverse drug reactions (CADR). Guidelines have been recently published for drug skin tests to standardize the management of patients suffering from CADR in European dermatological departments. Three sorts of drug skin tests can be performed, each investigating specific immunological mechanisms: delayed cellular hypersensitivity with patch tests (PT), immediate hypersensitivity with prick tests and both immediate or delayed hypersensitivity with intradermal tests (IDT). The mechanisms involved in inducing CADR are not well elucidated. The results of the drug skin tests depend on the drug and the mechanisms i.e. the clinical features of the CADR. 164 patients developed a CADR that could be attributed to one drug. After a patch test and a negative prick and intradermal test, positive drug skin tests were nevertheless obtained in 72% of the cases. Some urticarias are due to an immediate IgE related hypersensitivity; in such cases prick tests and IDT performed with sequential dilutions can have immediate positive results. Vasculitis is related to circulating immune complexes and cannot be reproduced by skin tests. Delayed cellular hypersensitivity is involved in inducing maculopapular rashes, Baboon syndrome, localized or generalized eczema or acute generalized exanthematous pustulosis. In such CADR, drug PT or delayed positive reactions on IDT occur in more than 50% of the patients. Diluted drug patch tests can be positive in investigating drug rash with eosinophilia and systemic symptoms. As Stevens-Johnson and Lyell's syndromes are due to many both toxic and immunological mechanisms, drug skin tests are not of great value in investigating these severe CADR.
Barbaud
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Service de Dermatologie, Hôpital Mainger-Villemein-Fournier, Nancy, France. abarbaud@chu-nancy.fr
D003875:Drug Eruptions / Q000175:diagnosis* / Q000503:physiopathology*; D006801:Humans; D012867:Skin / Q000187:drug effects / Q000503:physiopathology*; D012882:Skin Tests