A 78-year-old Japanese man presented with lower back pain of 8 months' duration and bilateral leg pain of 1 month's duration. He had developed tuberculous pleuritis at 11 years of age. The patient had no history of trauma. His mother had a history of tuberculosis when he was 7 years old. He had no occupational or avocational exposure to wet soil or water. He had never traveled abroad.
At the presentation, the patient's vital signs were normal. Physical examination revealed an increased patellar tendon reflex on the left side and bilaterally decreased Achilles tendon reflexes. He was capable of bending both knees and moving both ankles as intended. Blood tests showed normal white blood cell counts and elevated C-reactive protein level (6.6 mg/dL) and erythrocyte sedimentation rate (55 mm/hour). Mild renal dysfunction was observed, with a creatinine of 1.35 mg/dL. The soluble interleukin-2 receptor level was elevated to 764 U/mL. T-SPOT.TB (Oxford Immunotec) and anti-human immunodeficiency virus antigens/antibodies tested negative. Computed tomography revealed a fracture with osteolytic changes in Th12-L1 vertebrae and a mass in the right kidney (Figure 1). Magnetic resonance imaging revealed Th12-L1 vertebral fractures and protrusion of the vertebrae into the spinal canal (Figure 2).
Three days after presentation, he underwent posterior vertebral decompression and percutaneous thoracolumbar root screw fixation for neurological deficits and vertebral biopsy for a pathological vertebral fracture. No remarkable abscess or necrotic tissue was observed intraoperatively. Vertebral tissue samples were negative for general bacterial culture, concentrated fluorochrome smear microscopy, and nucleic acid amplification testing for Mycobacterium tuberculosis. Pathological examination of the vertebral tissue showed caseous necrosis surrounded by epithelial granulomas and a few multinucleated Langhans giant cells (Figure 3). A few acid-fast bacilli were found on auramine-rhodamine and acid-fast stains; no neoplastic lesions were detected (Figure 4). Based on these findings, the patient was presumed to have tuberculous spondylitis, and oral rifampicin, isoniazid, ethambutol (EMB), and pyrazinamide administration was commenced on the eighth postoperative day.
Bacteriological investigation revealed the growth from vertebral tissue cultures on 2% Ogawa medium (Kyokuto Pharmaceuticals) in the second week at 30 C and in the third week at 37 C, respectively. Cultures on a liquid medium (Mycobacteria Growth Indicator Tube, Becton Dickinson) at 37 C were negative for 12 weeks. Bacteria and mycobacteria were not isolated from sputum or urine cultures. Mycobacterium tuberculosis group antigen or mycobacterial protein fraction from bacille Calmette-Guerin of Rm 0.64 in electrophoresis tested negative. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry indicated an NTM suggestive of M arupense infection. Based on these results, pyrazinamide was switched to clarithromycin (CLR) on postoperative day 27. Subsequent identification tests revealed 100% homology with M arupense on 16S ribosomal RNA (rRNA), 99.75% on hsp65, and 98.91% on rpoB gene sequencing. The relationship between 16S rRNA gene sequence of this isolate and that of other species of Mycobacterium terrae complex (MTC) is shown in the Supplementary Figure. Drug susceptibility testing showed that the isolate was susceptible to rifabutin (RFB), EMB, and CLR based on the interpretation for Mycobacterium kansasii of the Clinical and Laboratory Standards Institute document M62 (Table 1). The regimen was then adjusted to 3-drug combination therapy of RFB, CLR, and EMB on postoperative day 126. Subsequently, neutropenia and thrombocytopenia, likely due to the interaction between RFB and CLR, were observed, and RFB was switched to faropenem (FRPM) on a postoperative day 160. Antimicrobial therapy was completed 1 year after the initiation of CLR treatment. His symptoms gradually improved, and his condition has been stable for 2 years after treatment. A partial nephrectomy was performed for renal cancer.