Cerebral conundrum: Nocardia-induced focal neurologic deficit in an immunocompetent patient: A case report

Background Nocardiosis is an uncommon, yet serious infection that predominantly affects immunocompromised individuals. Although cases can occur in immunocompetent hosts, very few are without identifiable risk factors, which often leads to delayed diagnosis. Specifically, central nervous system (CNS) involvement may present diagnostic challenges due to its resemblance to stroke, malignancy, or other structural lesions. Case Presentation A 73-year-old immunocompetent woman with Parkinson’s disease, atrial fibrillation without systemic anticoagulation, and a remote history of breast cancer presented with acute left-sided weakness, facial droop, slurred speech, and episodic seizure-like activity. Imaging revealed a right frontoparietal ring-enhancing mass initially concerning for solitary metastasis. Craniotomy revealed purulent material, and intraoperative aerobic and acid-fast bacilli cultures grew Nocardia farcinica / kroppenstedtii . The patient exhibited clinical improvement in her focal neurologic deficits upon treatment with intravenous (IV) trimethoprim-sulfamethoxazole and meropenem while inpatient. After discharge, repeat imaging at 6 months demonstrated resolution of the brain mass, with new right frontoparietal encephalomalacia, and at 2 years demonstrated evolving gliosis of the right precentral and middle frontal gyri. Discussion This case illustrates a rare diagnosis of CNS nocardiosis and highlights the diagnostic uncertainty of nocardial infection in immunocompetent hosts. Imaging cannot reliably distinguish a nocardial abscess from neoplasm, making definitive tissue diagnosis essential for early treatment and clinical improvement. Conclusion Clinicians should consider Nocardia in the differential diagnosis of ring-enhancing CNS lesions, even in immunocompetent individuals. Early surgical diagnosis and targeted antimicrobial therapy are crucial due to high morbidity and mortality associated with CNS nocardiosis.