Background: DRESS (drug reaction with eosinophilia and systemic symptoms) syndrome is characterized by fever, rash, eosinophilia, and multiorgan failure. Previous reports have described differences in clinical and laboratory findings of DRESS syndrome depending on the inducing drug. Piperacillin has been reported as the drug responsible for this syndrome in 3 patients.

Objective: To analyze and describe the clinical, laboratory, and allergy study findings of piperacillin-induced DRESS. Patients and Methods: Retrospective case series of patients diagnosed with DRESS associated with piperacillin-tazobactam (Pip/Taz) according to the Kardaun diagnostic score criteria. Assessment of causality was established using the Spanish Pharmacovigilance System and the lymphocyte transformation test (LTT). The allergy study included skin and epicutaneous tests.

Results: Eight patients were diagnosed with DRESS due to Pip/Taz (3 probable and 5 definite cases). Skin rash was observed in all cases and facial edema in 50%; the mean latency period was 18 days. Fever was present in 7 patients. Liver and kidney injuries were detected in 6 and 3 patients, respectively. All patients had eosinophilia and a full recovery. The LTT to Pip/Taz was strongly positive in all patients, with a stimulation index of over 6. Three of 3 patients had a positive intradermal test to Pip/Taz, and 1 of 4 had a positive patch test. All patients had a negative LTT to carbapenems.

Conclusions: We have reported on the first case series of piperacillin-induced DRESS. A latency period of 18 days, skin rash, eosinophilia, fever, liver injury, and good prognosis were the most common features. The allergy study, and the LTT in particular, was highly useful for identifying Pip/Taz as the culprit drug and piperacillin as the responsible active ingredient.

Key words: Allergy study. DRESS syndrome. Drug reaction with eosinophilia and systemic symptoms. Lymphocyte transformation test. Piperacillin-tazobactam.