A Case of Mexiletine-induced Hypersensitivity Syndrome Presenting as Eosinophilic Pneumonia

An 82-yr-old man was presented with fever and cough accompanied by generalized erythematous rash. He had taken mexiletine for 5 months, as he had been diagnosed with dilated cardiomyopathy and ventricular arrhythmia. Laboratory studies showed peripheral blood eosinophilia and elevated liver transaminase levels. Chest radiographs showed multiple nodular consolidations in both lungs. Biopsies of the lung and skin lesions revealed eosinophilic infiltration. After a thorough review of his medication history, mexiletine was suspected as the etiologic agent. After discontinuing the mexiletine and starting oral prednisolone, the patient improved, and the skin and lung lesions disappeared. Subsequently, mexiletine was confirmed as the causative agent based on a positive patch test. Drug-induced hypersensitivity syndrome is a severe adverse reaction to drugs and results from treatment with anticonvulsants, allopurinol, sulfonamides, and many other drugs. Several cases of mexiletine-induced hypersensitivity syndrome have been reported in older Japanese males with manifestation of fever, rash, peripheral blood eosinophilia, liver dysfunction without other organ involvement. Here, we report a case of mexiletine-induced hypersensitivity syndrome which presented as eosinophilic pneumonia in a Korean male.