Isoniazid (INH)-induced eosinophilic exudative pleural effusion and lupus erythematosus. A clinical reminder of drug side effects.

A 75-year-female with a history of Isoniazid (INH) therapy for latent tuberculosis, was admitted with a 4-week duration of dyspnea, cough, and pleuritic chest pain. She was treated with intravenous antibiotics for a diagnosis of pneumonia. Her stay was complicated by development of recurrent, exudative eosinophilic pleural effusions (EPEs). When symptoms continued to worsen and she developed joint pain and anasarca and did not respond to the antibiotics, a rheumatologic work-up was performed. She was found to have positive anti-double stranded-DNA antibodies and anti-histone antibodies; thus, a diagnosis of drug-induced lupus, secondary to INH, was made. INH was discontinued, and the patient was started on prednisone; within weeks her symptoms resolved. This case illustrates a unique side effect of INH that caused exudative EPEs and drug-induced lupus with positive anti-dsDNA.