Anticonvulsant hypersensitivity syndrome (AHS) is a rare, severe drug hypersensitivity reaction included in the drug-related rash with eosinophilia and systemic symptoms syndrome (DRESS), in which a transient state of immune suppression and reactivation of latent virus infections have been observed.
We describe 5 patients who developed neosensitization to different drugs taken during a previous episode of anticonvulsant-related DRESS, in whom skin prick, intradermal and/or patch tests were performed to confirm the diagnosis of drug hypersensitivity.
In 1 patient, transient hypogammaglobulinemia was observed during the AHS. Four of the 5 patients developed a delayed skin eruption or a delayed systemic hypersensitivity reaction after intake of a drug that they had also taken during a previous anticonvulsant DRESS which had occurred months or years earlier; in the fifth, a possible reaction was prevented thanks to the allergy workup. The diagnosis of drug allergy was demonstrated by positive delayed reaction to intradermal test with amoxicillin in 2 cases, positive patch tests to paracetamol and amitriptyline in 2 cases, and by clinical evidence of ceftriaxone erythroderma in one. The possibility of neosensitization to drugs administered during anticonvulsant-related DRESS should be considered. A transient state of immunosuppression induced during the anticonvulsant-related DRESS may trigger latent virus reactivation and massive nonspecific immune system response, which may lead to breakdown of tolerance to other drugs present at that time in the organism.

Key words: Anticonvulsants. Carbamazepine. DRESS. Drug adverse reactions. Drug neosensitization. Phenytoin.