Isoniazid-induced Lupus: When the Cure Can be Lethal

A 50-year-old female with a past medical history of bone tuberculosis diagnosed nine months ago was admitted in our infirmary for persistent fever with no evident cause. The patient was treated with isoniazid, rifampicin, pyrazinamide, and ethambutol for seven months and for the past two months, she was taking isoniazid and rifampicin. She went to our emergency room (ER) for back pain and fever that she had been experiencing for the last month. She was admitted with suspicion of disseminated tuberculosis that was never confirmed. Physical examination was unremarkable. Blood tests showed an elevation of inflammation parameters. A computed tomography (CT) scan of the chest showed a mild pleural effusion. She remained with fever during the three weeks in the infirmary while undergoing many other studies that were all negative. The back pain would change sides, and three consecutive thoracic radiographies showed a small-sized pleural effusion that was either predominantly right-sided or left-sided. Several differential diagnoses were considered in the process, namely an active infection, neoplasia, or autoimmune disease. The search for circulating lupus anticoagulant was positive. Antinuclear antibodies (ANA) were positive and the anti-histone antibody was strongly positive. At this point, we suspected a drug-induced lupus diagnosis, and isoniazid was discontinued. Following discontinuation of isoniazid, back pain and fever subsided and patient was discharged after one week. This case is a diagnostic challenge because of the rarity and symptom severity of isoniazid-induced lupus. Isoniazid rarely induced this lupus-like syndrome, with an incidence of considerably less than 1%.