A 43-year-old woman with a history of acute myeloid leukemia was admitted to our hospital in July 12, 2020 for repeated fever during the previous 2 months, and a persistent fever for the previous 4 days. Two months previously, she presented with a fever, cough, and expectoration. At that time she was diagnosed with "invasive pulmonary fungal disease" and was given oral voriconazole and biapenem as empirical therapy. Her condition improved gradually after this treatment. Four days prior to the current admission, she was admitted because of a relapse of fever, with a body temperature of 38.6 C.
A physical examination showed that her underarm temperature was
38.6 C, pulse was 108 beats/min, breathing was 25 breaths/min, and blood pressure was 109/67 mmHg. There was dullness on lung percussion and strong vocal fremitus with fine crackles in the left lung. Laboratory investigations showed a white blood cell count of 3.61x109 per L (normal: 3.5-9.5), red blood cell count of 3.22x1012 per L (normal: 3.8-5.1), hemoglobin concentration of 112g/L(normal: 110-150 g/l), platelet count of 268x109 per L (normal: 125-350), and absolute neutrophil count of 2.02x109 per L (norma: 1.8-6.3). In addition, the 1,3-beta-D-glucan level was normal, and an aspergillus antigen test for serum galactomannan was negative. The liver function, renal function, and electrolyte levels were all normal. There were negative results for antinuclear antibody (ANA), extractable nuclear antigen (ENA), antineutrophil cytoplasmic antibodies (ANCA), TB spot test and TB blood culture. Computed tomography (CT) on July 14, 2020 indicated consolidation in the left lower lung (  Figure 1  ). Therefore, we made a preliminary diagnosis of CAP with acute myeloid leukemia.
As the empirical anti-infective therapy, we administered biapenem (0.3 g, Q6H), but her condition did not improve. On day 3 after admission, the urinary antigen tests for Streptococcus pneumonia and anti-Legionella antibodies were negative. To identify the etiology, we collected BALF and tested it with mNGS using the MiSeq platform (Illumina). The results indicated 46 sequence readings of Legionella pneumophila ( Table 1 ) with a coverage of 0.07% ( Table 2 ). Sequencing of 16s rRNA sequencing using Nanopore GridION also detected the 17 L.pneumophila sequences in the same DNA sample.
Combined with her medical history, clinical symptoms, physical signs, results from auxiliary examinations, and mNGS, we diagnosed the patient with Legionella pneumonia and adjusted the treatment plan to intravenous moxifloxacin and azithromycin. After 14 days of treatment in the hospital, the patient's fever had resolved, and she was discharged, and prescribed antimicrobial agents as sequential oral therapy. A CT follow-up after one month (August 16, 2020) indicated the pulmonary lesions in the left lower lung were significantly absorbed ( Figure 2 ). Records of her white blood cell count, C-reactive protein, body temperature, and other results indicated gradual improvements during her hospital stay ( Figure 3 ).