A 44-year-old obese black male patient with autosomal dominant polycystic kidney disease was hospitalized in August 2021 to explore pulmonary nodules incidentally discovered on a computed tomography performed while the patient was hospitalized for a renal cyst infection.
The patient was born in Mali but had lived in France for the past 43 years. He received a kidney transplant in February 2018. He had no pre-existing lung disease and declared a ten pack-year smoking history. The immunosuppressive regimen consisted of prednisone, mycophenolate mofetil and cyclosporine. Cotrimoxazole prophylaxis against Pneumocystis jirovecii pneumonia was started after transplantation. Pre-transplant screening for latent tuberculosis infection was not performed.
The post transplantation period was marked by a recurrent lymphocele treated by laparoscopic marsupialization. In June 2021, the patient presented with fever and a renal cyst infection was suspected. Despite no bacteriological confirmation, he received a 4-week course of ceftriaxone. Thoracoabdominal CT-scan showed pulmonary nodules that led to subsequent pulmonary explorations. Physical examination including lung auscultation was unremarkable. The body mass index reached 34 kg/m2. White blood cell count was 4,14 G/L and C-reactive protein level was 7 mg/l. Serum fungal biomarkers (galactomannan and B-D-glucan), as well as blood aspergillus PCR assay were negative. Glomerular filtration rate measured by 51Cr-EDTA clearance was 54 ml/min. Computed tomography revealed multiple nodules in both lungs, without interstitial infiltrates (Fig. 1A and 1B). The bronchoalveolar lavage (BAL) fluid contained many cells with macrophage predominance (960,000 cells/ml, 94 % macrophages, 5 % lymphocytes, 1 % neutrophils). Standard bacteriological and fungal cultures were negative and auramine staining did not show any acid-fast bacilli. Whole-body positron emission tomography (PET) depicted moderated hypermetabolism of pulmonary nodules (SUVmax: 3.5) without any other abnormal fixation (Fig. 1C). Trans-thoracic lung biopsy was performed and evidenced non-caseating epithelioid and giant cellular granulomas with a negative Ziehl-Neelsen staining. After 49 days, Mycobacterium xenopi grew in the bronchial aspiration culture. No antimicrobial susceptibility testing was performed considering the limited relevance of this test to guide antibiotic treatment.
Blood and urine cultures were negative for mycobacteria. Pulmonary nodules increased in size at one-month follow-up CT scan, despite the patient remaining afebrile without any respiratory symptoms. Mycophenolate mofetil dosing was lowered and an antimycobacterial treatment containing rifabutin, ethambutol and azithromycin was initiated. Immunosuppressive drugs were carefully monitored, and doses were adapted for interaction with rifabutin: prednisone and cyclosporine doses were increased by 50 % and 100 % respectively. Several days later, the patient discontinued treatment because of asthenia, fever and myalgias. Adverse events related to rifabutin were suspected and the treatment was switched off for moxifloxacin. The patient's condition improved, and he quickly became afebrile after rifabutin discontinuation. Two months later, computed tomography showed that pulmonary nodules decreased in size. Graft function remained stable. A 12-month treatment was planned.