An 85-year-old man without a history of tuberculosis visited our clinic with a 3-day history of a fever and anorexia. He suffered from Alzheimer's disease and lived in a long-term care facility. A physical examination revealed a body temperature of 36.6 C, a percutaneous oxygen saturation (SpO2) of 95% (room air), a respiratory rate (RR) of 20 pm, a blood pressure of 135/78 mmHg, and a heart rate (HR) of 71 bpm. Laboratory tests revealed a decreased leukocyte count (3,100 cells/muL) and elevated serum levels of C-reactive protein (CRP; 5.2 mg/dL). Chest X-ray taken at the first visit (Fig. 1A) showed infiltrates in both lung fields but predominantly on the right. We did not perform chest CT at that time. Although a sputum-acid-fast smear test was negative, we were unable to exclude the possibility of pulmonary tuberculosis because of multiple patchy infiltrates on chest X-ray; we therefore prescribed TFLX, which does not cover M. tuberculosis. A Gram stain analysis is not routinely performed at our clinic. Methicillin-resistant Staphylococcus aureus (MRSA) was isolated from the sputum culture, but we initially regarded this as colonization. Rapid urine antigen test for Streptococcus pneumoniae and Legionella pneumophila were both negative.
The patient's symptoms gradually disappeared after a few days. Because chest X-ray taken seven days from the start of TFLX administration revealed improvement (Fig. 1B), we diagnosed him with general bacterial pneumonia and ended TFLX after 14 days. Therefore, we did not follow up his chest X-ray until the infiltrates completely disappeared. However, at three weeks after the end of TFLX administration, the fever and anorexia relapsed, and he returned to the hospital. A physical examination revealed a body temperature of 37.4C, an RR of 24 pm, a SpO2 of 95% (room air), a blood pressure of 164/86 mmHg, and a HR of 88 bpm. Laboratory tests revealed a normal leukocyte count (4,150 cells/muL) and elevated serum levels of CRP (4.8 mg/dL). Chest X-ray (Fig. 1C) revealed expanded infiltrates in both lung fields, and chest CT showed consolidation with a tree-in-bud appearance (Fig. 2). A sputum-acid-fast smear test was positive, and M. tuberculosis was isolated from the culture. After starting treatment with multi-antituberculous drugs including ethambutol, isoniazid and rifampin, his symptoms, pulmonary infiltrates on X-ray and CRP levels gradually improved (Fig. 1D).