First reported case of disseminated Nocardia kroppenstedtii sp nov. infection presenting with brain abscess and endocarditis in an immunocompromised patient with mantle cell lymphoma: challenges in diagnosis and treatment.

A 72-year-old man with a history of blastoid variant stage IV relapsed refractory mantle cell lymphoma presented with new central nervous system (CNS) symptoms. Brain imaging was positive for rim-enhancing lesions along with a mitral valve mass on the echocardiogram. It was a challenge to establish the exact aetiology of these lesions in this patient. He was empirically treated with chemotherapy on the presumption that the brain lesions were secondary to progressive malignancy. However, brain biopsy was negative for malignancy and blood cultures were found positive for Nocardia kroppenstedtii sp nov. He subsequently improved with antibiotic therapy. Disseminated Nocardia can present with multiorgan involvement. Clinical and microbiological diagnosis can be challenging. Antimicrobial treatment-related side effects require close monitoring, and dosage changes or therapy adjustments may be necessary.