Patch tests for diagnosis of delayed hypersensitivity to cephalosporins.

Abstract Background Few studies have reported delayed hypersensitivity reactions to systemically administered cephalosporins. The diagnostic procedures and extracts for these reactions are not standardized, and little is known about the extent of cross reactivity among different cephalosporins. Cases report We report 2 cases of delayed hypersensitivity reactions due to cephalosporins presenting as erythrodermia. Case 1. An 80-year-old man developed generalized pruritus and erythema 2-3 days after starting treatment with cefuroxime. The drug was stopped and antihistamines and corticosteroids were administered. The patient improved 5-6 days later, and mild superficial desquamation was observed. Case 2. A 66-year-old woman experienced similar symptoms 4-5 days after beginning cefazolin. She reported a similar reaction with ceftazidime 8 years previously. Methods and results Skin prick tests and specific IgE against penicillin G and V, amoxicillin, ampicillin and cephalosporins were negative. Intradermal tests with ceftazidime and cefazolin were positive in case 2 at delayed reading. Patch tests using benzylpenicillin, ampicillin, amoxicillin, several cephalosporins, aztreonam and imipenem were positive to all the cephalosporins tested (at 48 and 96 hours) and were negative to the other betalactams. Controlled administration of amoxicillin, benzylpenicillin, aztreonam and imipenem was well tolerated by both patients. Conclusions 1) We report 2 cases of delayed hypersensitivity reactions due to cephalosporins presenting as erythrodermia. 2) Epicutaneous tests were useful for diagnosis. 3) Both patients tested positive to all cephalosporins and negative to other betalactams.