An Ofloxacin-Induced Anaphylaxis through an IgG4-Mediated but Not IgE-Mediated Basophil Activation Mechanism

We report a case of 20-year-old female patient with ofloxacin-induced anaphylaxis mediated by IgG4 antibody. One of second-generation fluoroquinolone, ofloxacin is prescribed widely to treat bacterial infections. Reports of serious hypersensitivity reactions to quinolone are increasing due to high consumption worldwide [1]. The pathogenesis of anaphylaxis caused by ofloxacin is not yet fully understood, as it is not commonly reported. There has been a report demonstrating high serum specific IgE levels to ofloxacin-human serum albumin (HSA) conjugate using enzymelinked immunosorbent assay (ELISA), enzyme-linked immunospecific assay [2]; however, this is the first report to suggest an IgG4-mediated but not IgE-mediated mechanism in a patient with ofloxacin-induced anaphylaxis. A 20-year-old female with allergic rhinitis was referred to our department for the evaluation of anaphylaxis because she had experienced generalized urticaria and dyspnea with wheezing, and hoarseness within 1 hour after oral ingestion of ofloxacin 100 mg. It was her first ingestion of ofloxacin. The patient had a history of acute, generalized urticaria and drug allergy to nonsteroidal anti-inflammatory drugs. Her mother had a history of bronchial asthma. At the initial visit, no abnormal findings were noted on physical examination and radiography/spirometry results. Her serum total IgE level was 42 kU/L. Allergy skin prick tests showed positive responses to Dermatophagoides farinae and D. pteronyssinus, but negative responses to ofloxacin at concentrations of 0.1−10 mg/ml, with a positive control being a mean wheal size of 4 mm to histamine. Ofloxacin-HSA conjugate was conducted to investigate immunologic mechanisms to detect serum specific IgE antibody to ofloxacin-HSA conjugate using ELISA as