Diagnostic Challenges of Pulmonary Nocardiosis in Lung Transplant Recipients

Abstract Introduction Lung transplant recipients are increasingly susceptible to opportunistic infections. Pulmonary nocardiosis can affect up to 4.2% of lung transplant recipients. Diagnosing pulmonary nocardiosis in a timely fashion is critical as the mortality can be up to 30%. Despite numerous ways to diagnose nocardia, diagnosis can often be delayed, with a median diagnostic time of 9 to 13.6 days from initial sampling. Here, we present a case of nocardiosis in a lung transplant patient, where multiple tissue sampling modalities were required for diagnosis. Case A 68-year-old male with a history of lung transplant for idiopathic pulmonary fibrosis presented to the hospital 3 years post-transplant with pleuritic chest pain. His outpatient immunosuppression regiment consisted of tacrolimus, azathioprine and prednisone. He took trimethoprim/sulfamethoxazole (TMP-SMX), isavuconazole and azithromycin for antimicrobial prophylaxis. Six months prior to admission, the patient was started on voriconazole for a positive 1-3-Β-D-glucan. Five months prior to admission, the patient had a CT chest showing new indeterminate solid nodules in the left lower lobe (LLL). He had a bronchoscopy, bronchoalveolar lavage (BAL) and transbronchial biopsy (TBBX) which were negative for rejection but culture grew Pseudomonas aeruginosa. Repeat CT scan showed increased nodules within the LLL and patient was subsequently switched to isavuconazole empirically as an outpatient. During this admission, labs were notable for hyperkalemia and a therapeutic tacrolimus level. A CT pulmonary angiogram was notable for a consolidative opacity in the LLL, a left sided pleural effusion and numerous well-circumscribed soft tissue nodules in the transplanted lung. A bronchoscopy, BAL and TBBX were performed. Results were negative for infection, rejection, and malignancy. A chest tube was placed for drainage of the left pleural effusion. Pleural fluid cultures were negative and cytology was negative for malignancy. A transthoracic needle aspiration of the LLL lesion was ultimately performed and the fine needle aspiration results were positive for nocardia. A CT head and MRI brain were performed to evaluate for dissemination, both of which were negative for intracranial involvement. The patient was started on therapeutic TMP-SMX for pulmonary nocardiosis and discharged home with close outpatient follow up. Conclusion This case highlights the diagnostic challenges of nocardiosis in a lung transplant recipient. Although the patient was on TMP-SMX for Pneumocystis jirovecii prophylaxis, he still had a breakthrough infection, emphasizing the limitation of this regimen. Timely diagnosis combined with appropriate antimicrobial therapy are crucial to reducing the morbidity and mortality associated with nocardiosis.