We report a 65-year-old man who attended teaching hospital at Henan with a 10-day history of fever, intermittent cough, expectoration and wheezing. Five days prior to admission, the patient had been treated with anti-infective drugs at his local hospital (such as rifampicin, ethambutol, clarithromycin, piperacillin sodium and tazobactam sodium, and levofloxacin), but the therapeutic effect was not good. He had a past medical history of chronic obstructive pulmonary disease (COPD). He lived in the rural Henan province, China, and has no recent travel history out of the province.
Physical examination showed that his underarm temperature was 38  C, pulse was 108 beats/min, breathing was 25 beats/min, and the patient had a barrel-shaped chest, partial collapse of the upper left anterior thorax, clear voice during percussion of both lungs, regular breathing, and scattered dry and wet rales on auscultation of the lungs.
The laboratory studies revealed elevated erythrocyte sedimentation rate (69 mm/h), C-reactive protein (61.77 mg/L), rheumatoid factor quantification (74.7I U/mL), procalcitonin (0.06 ng/mL), blood glucose (7 mmol/L), cancer antigen 125 (35.21 U/mL), neuron specific enolase (20.56 ng/mL) and D-dimer (1.41 mug/mL). While the percent of lymphocytes (19%), red blood cell (3.47 x 109/L), hemoglobin (106 g/L), serum potassium (3.32 mmol/L), and albumin (27.1 g/L) were reduced. Other indicators, including GM test, T-SPOT.TB, Xpert MTB (Sputum) and antistreptococcal "o" quantification were negative.
Coughed up sputum smear examination: no bacteria and fungi were found in the microscopic examination, and acid-fast positive bacilli (+) were found in the microscopic examination. It was necessary to further distinguish Mycobacterium tuberculosis and non-tuberculous Mycobacteria.
Chest computed tomography scan indicated multiple flaky, strand-like and light mist-like high-density shadows in both lung fields. Visible effusion in the left pleural cavity (Figure 1). Hence, he was preliminarily diagnosed with lung infection and the nature of the upper right lung space to be investigated. We decided to treat the patient with intravenous biapenem for empirical anti-infective and oral rifabutin, ethambutol hydrochloride tablets and clarithromycin sustained-release tablets for anti-tuberculosis treatment, but his condition did not improve.
On day 3 of the admission, a bronchoscopy was performed, and the apical bronchus of the right upper lobe was blindly examined. Pathological results showed granulomatous inflammation with necrosis, special staining results showed acid-fast (-), molecular pathological results showed Mycobacterium tuberculosis DNA determination (TB-DNA) (PCR) (-) (Figure 2). Bronchoalveolar lavage fluid (BALF) was collected for mNGS and M. avium complex was detected (Table 1). Combined with clinical symptoms, laboratory test results and characteristics of MAC, the patient was diagnosed with MAC lung disease. Discontinued biapenem and switched to intravenous amikacin and oral compound sulfa tablets; and continued oral rifabutin, ethambutol hydrochloride tablets and clarithromycin. After 7 days of treatment, the patient's fever, cough, expectoration and wheezing had gradually improved. At the follow-up 3 months later, the patient's above symptoms had been completely relieved.