In vitro interferon-gamma release test in patients with drug-induced pemphigus

Background: Drug-specific CD8+ TH1 lymphocytes have been found in the peipheral blood and involved skin of patients with drug-induced bullous exanthems. Objectives: To determine whether the interferon-gamma release test can identify culprit drugs in pemphigus patients. Methods: Clinical and laboratory workup for pemphigus was performed in 14 pemphigus vulgaris patients who had been exposed to drugs, and the IFNγ release test was conducted on their lymphocytes from heparinized venous blood cultured with medium, phytohemagglutinin and one of 32 drugs, or medium and phytohemagglutinin alone. Results: Ten of the patients and 13 of the 32 drugs exhibited a positve response to the test. Eight of the 10 patients with positive IFNγ test results had a less severe course of the disease, with fast reduction in steroid dosage. Conclusion: The findings demonstrate both the ability of the IFNγ release test to identify drugs that can induce pemphigus, and its usefulness in the diagnostic workup of pemphigus patients.