D1.94 - Vancomycin- and Meropenem-Induced DRESS Confirmed by the Lymphocyte Transformation Test: A Synergistic Effect in Severe Drug Reactions

DRESS is a rare but severe cutaneous adverse drug reaction characterized by cutaneous and systemic manifestations. It is most commonly triggered by multiple drug exposure, particularly antibiotics and antiepileptic drugs, and latent herpesvirus reactivation is thought to contribute to its pathophysiology.The variable clinical course, prolonged latency period of 2–9 weeks, exposure to multiple drugs, and the contraindication of drug provocation tests complicate identification of the culprit drug and future safe drug selection. Therefore,in vitro diagnostic approaches are preferred in DRESS due to their favorable safety profile. Here, we present a DRESS case that developed after multiple antibiotic exposure during treatment for complicated pneumonia, in which the etiology was clarified using the LTT.

Culprit drugs were investigated using LTT(³H-thymidine incorporation).A stimulation index (SI) >2 was considered positive.

An 11-year-old girl initially received empirical oseltamivir for suspected influenza at an outside center.Two days later,she was re-evaluated for flank pain and admitted to intensive care for lobar pneumonia and empyema. Intravenous vancomycin and meropenem plus oral clarithromycin were initiated.After a 21-day stay, she presented three days after discharge with fever and widespread rash. Examination revealed diffuse maculopapular rash, facial edema, desquamation of the extremities, cervical lymphadenopathy, decreased breath sounds at the right lung base, and a grade 2/6 systolic murmur. Laboratory tests showed eosinophilia and elevated creatinine.  EBV and CMV IgM were positive, whereas plasma PCR assays were negative. The RegiSCAR score was 5, confirming DRESS. Intravenous corticosteroids were initiated, and levofloxacin was administered for complicated pneumonia. Clinical and laboratory improvement was observed.Antibiotic therapy was discontinued after seven days, and she was discharged on oral prednisolone with a six-week taper. LTT performed five weeks after rash onset was positive for vancomycin and meropenem (Table 1).

This report highlights the diagnostic value of LTT in a DRESS case with multiple antibiotic exposure and complicated infection.Identification of two different antibiotic classes as culprit drugs suggests a possible synergistic immune activation leading to multiple drug hypersensitivity.By overcoming the limitations and safety risks of in vivo testing,LTT may guide safer future antibiotic selection.Written informed consent for publication was obtained from the patient’s legal guardian.