A 66-year-old woman, a retired hotel caretaker, was admitted to the Respiratory Department of the First Hospital of the China Medical University with the chief complaint of 'intermittent fever and lung occupation for 2 months'. Six months prior, the patient was diagnosed with primary nephrotic syndrome (idiopathic membranous nephropathy stage I) and chronic renal insufficiency (G5 stage). After tacrolimus administration, the patient received corticosteroid therapy (oral prednisone 50 mg once a day, 5 mg reduced every half month) combined with cyclophosphamide (1.0 g per month), and her kidney function was found to have improved since then (Figure 1C and D).
Three months prior, her chest computed tomography (CT) scan showed multiple nodules in both lungs (Figure 2B), which were not observed in prior CT scans (Figure 2A). An enhanced chest CT also revealed irregular nodules around the right lung hilum with mild enhancement, right pleural effusion, and enlarged mediastinal and right hilar lymph nodes (Figure 2C). Initially, these lesions were suspected to be malignant, however, after administration of cephalosporin combined with levofloxacin intravenous for 3 weeks, including three times for bronchoscopies and tissue biopsies and one time for mediastinal lymph nodes inspected by endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA) were all failed to detect any malignant tissue, aside from benign pathologic changes such as chronic inflammation. To rule out the possibility of tuberculosis, relevant blood tests were performed, all of which had a negative result. Notably, the patient persistently presented with an intermittent fever during hospitalization, and her highest body temperature was reported to reach 39.8 C. As such, the patient was transferred to our department for further diagnosis and treatment, following a multidisciplinary team consultation.
The patient still presented with fever without chills, and the highest body temperature reached 38 C. On physical examination, rough breath sounds were heard in both lungs. Moreover, significantly increased levels of inflammation-related indicators (WBC: 26.72x109 /L, NE: 23.14x109/L, CRP: 57.4 mg/L, PCT: 0.206 ng/L) were seen on laboratory examinations (Figure 1A and B), along with increasing levels of coagulation indicators (Fg: 6.31 g/L, D-D: 4.4 ug/mL), and slightly higher levels of serum tumour markers (CA125: 63 U/mL, CA199: 38.4 U/mL, Cyfra21-1: 3.38U/mL). After testing for penicillin allergy, intravenous piperacillin-tazobactam (2.5 g every 12 hours) was initiated, and prednisone was still used for primary nephrotic syndrome concurrently. For further diagnosis, the patient underwent endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) biopsy again, and cultures from pulmonary lesions revealed Nocardia species which was a gram-positive, partial acid-fast positive, rod-shaped bacterium (Figure 3A-C). A further species identification was subjected to MALDI-TOF MS (VITEK  MS, BioMerieux), which was identified as Nocardia farcinica (99.9% confidence).
Following pathological diagnosis, the patient underwent brain contrast-enhanced MRI and abdominal enhanced CT scans to exclude other foci. The brain contrast-enhanced magnetic resonance imaging (MRI) images showed mixed solid cystic lesions (Figure 4A), additional diffusion-weighted imaging (DWI) results are showed in Figure 5. Meanwhile, on whole-abdominal-enhanced CT, right abdominal encapsulated effusion and space-occupying lesions were reported (Figure 6B), which were not found in the previous inspection (Figure 6A). We administered to intravenous meropenem (1 g every 12 hours) and oral TMP-SMX (3 pieces every 8 hours, each piece containing 80 mg of trimethoprim and 400mg of sulfamethoxazole). About half month later, another brain contrast-enhanced MRI was performed, revealing the ring-like enhancement lesion was smaller than the previous one (Figure 4B), and a chest-enhanced CT scan also showed lesion size reduction (Figure 2D). Furthermore, laboratory tests revealed that infection-related indicators were all significantly lower than them before (Figure 1A and B). Since treatment was well tolerated with no adverse events, we advised the patient to continue oral TMP-SMX 3 pieces three times a day for 6 months, and to undergo regular follow-ups with blood tests and related imaging examinations. The relevant examination results are presented in Figures 1, 2E-G, 4C, 6C-E and 7. The clinical course is summarized in Figure 8.