Amoxicillin-Induced Hypersensitivity After DRESS To Carbamazepine

The anticonvulsant hypersensitivity syndrome, also known as drug rash eosinophilia and systemic symptoms (DRESS), is a rare but severe form of adverse cutaneous reaction. Several aromatic anticonvulsant drugs, such as carbamazepine (CBZ), phenytoin, or phenobarbital have been frequently associated with the onset of DRESS. Cross-reactivity among the aromatic anticonvulsants frequently occurs (40 to 80% of patients). However, cross reactivity with other drugs such as betalactams have exceptionally been reported. We report a clinical observation describing a DRESS associated with CBZ with a subsequent hypersensitivity to amoxicillin (AMX). A 34-year-old male with a 20-year history of epilepsy was treated with valproic acid and phenobarbital. As he had frequent convulsive fits, CBZ was added. Thirty-four days later, the patient developed hyperthermia (39.5°C), cervical lymphadenopathy, and generalized cutaneous exfoliated maculae and papulae. Biochemical investigation was characterized by a white cell count of (16.1 × 103/μL, 17% eosinophils) and increased levels of aspartate aminotransferase and alanine aminotransferase (50 and 116 IU/L, respectively). CBZ was discontinued. One month later, all the symptoms were progressively relieved. Six weeks after complete recovery, prick and patch skin tests were performed. They were strongly positive at 48-hour reading. About 2 years later, the patient exhibited an extensive pruritic skin rash, 2 days after AMX intake. Laboratory exams showed eosinophilia (7%) but neither elevated liver enzymes nor renal dysfunction. All these symptoms have disappeared 5 days after AMX withdrawal. Intradermal test to AMX was positive but not to other betalactams. Throughout this clinical observation, we report a CBZ-induced DRESS and describe the possibility of cross reactivity between CBZ and AMX. This cross reactivity was observed despite the lack of chemical similarity between both drugs.