An Unusual Presentation of Nocardiosis in an Allogeneic Transplant Recipient

Nocardiosis is a rare cause of opportunistic infection post hematopoietic stem cell transplant (HSCT) occurring in about 0.3% of patients. The risk factors include delayed immune reconstitution, prolonged neutropenia, and graft-versus-host disease. The most common site of infection is the lung, followed by the brain and the skin. Concomitant pulmonary and central nervous system (CNS) nocardiosis is an extremely rare entity as presented in our case. We present the case of a 72-year-old male at 137 days post transplant presenting with complaints of headache and slurred speech. A magnetic resonance imaging (MRI) brain scan revealed two ring-enhancing lesions: 1.6 cm in the right frontal lobe and 1 cm in the left parietal lobe. The patient had an outpatient computed tomography (CT) chest scan a month prior showing a 1.4 cm solid right upper lobe nodule prompting bronchoalveolar lavage (BAL) that was nondiagnostic. On repeat inpatient CT chest scan, the nodule had increased in size to 3.3 x 2.5 x 2.1 cm, prompting a percutaneous fine-needle aspiration biopsy. He was started on empiric trimethoprim-sulfamethoxazole (TMP-SMX) and liposomal amphotericin B. The tissue mycology and acid-fast cultures were reported positive for nocardia species. The patient was discharged on intravenous TMP-SMX. A follow-up CT chest scan and MRI brain scan four months later showed resolution of the right upper lobe nodule and significant decrease in size of the brain lesions. The patient will continue TMP-SMX for a total of nine to 12 months. Given the increase in transplant recipients and the ongoing risk of developing nocardiosis several months post transplant, there is a need for standardized diagnostic and treatment guidelines. Meanwhile, our case highlights the importance of aggressiveness in pursuing a prompt diagnosis including invasive procedures, if required, in order to begin specific treatment.