A 74-year-old man visited our hospital with dyspnea and a low-grade fever that had persisted for two weeks. He had no medical history of tuberculosis or use of anti-tuberculosis drugs. Chest radiography revealed a right pleural effusion (Fig. 1), and thoracentesis was performed. The pleural fluid was yellow, and laboratory findings were as follows: total cell count, >100 cells per high power field; lymphocytes, 79.2%; lactate dehydrogenase, 500 U/L; total protein, 4.9 g/dL; adenosine deaminase, 92.9 U/L. Furthermore, the interferon-gamma release assay results were positive. Thus, the patient was diagnosed with tuberculous pleurisy, and treatment with RFP (450 mg/day), isoniazid (INH, 300 mg/day), ethambutol (EB, 500 mg/day), and pyrazinamide (PZA, 1.2 g/day) was initiated.
Seven days after treatment initiation, the patient visited our hospital because of oral bleeding. Physical examination revealed mild oral bleeding and multiple purpuric lesions in his legs. The platelet count had decreased from 217 x 103/muL at baseline to 1 x 103/muL. Other laboratory findings were as follows: white blood cell count, 5300 cells/muL; hemoglobin, 11.4 g/dL; prothrombin time, 10.9 s; fibrinogen, 513 mg/dL; D-dimer, 10.7 mug/mL; C-reactive protein, 3.51 mg/dL; and platelet-associated immunoglobulin G (PAIgG), 286 ng/107 cells (normal value, less than 46 ng/107 cells). Liver and renal functions were normal. Markers for hepatitis B and C virus and cytomegalovirus were negative. Thrombocytopenia due to the effect of anti-tuberculosis drugs was suspected, and the four drugs were discontinued. Although platelet transfusion of 20 units was done on days one and two after treatment discontinuation, platelet count increased only up to 16 x 103/muL (Fig. 2). Since the bleeding subsided after the platelet transfusion and the platelet count gradually improved, we followed up until the side effects disappeared. The results of the drug-induced lymphocyte stimulation test were negative for the four drugs. On day 12 after discontinuation, levofloxacin was introduced, and EB, PZA, and INH (in this order) were reintroduced gradually. Since thrombocytopenia did not occur after restarting these drugs, he was diagnosed with rifampicin-induced thrombocytopenia. The patient was able to continue treatment since then, and the right pleural effusion disappeared.