Chronic Basal Ganglia Infarction With PCR‐Identified Paeniclostridium sordellii : A Rare Neuropathological Case Report

Background Within 1 month of diagnosis, 40% of patients with positive blood cultures will develop CNS complications. Rare pathogens, that is, Paeniclostridium sordellii , pose diagnostic challenges due to atypical presentations and detection difficulties. Case Presentation A 67‐year‐old man presented with metabolic encephalopathy and diabetes insipidus. Imaging showed bilateral basal ganglia abnormalities and an enhancing lesion near the anterior commissure, suspicious for neoplasm. Postmortem findings included reactive gliosis, atypical lymphocytic inflammation, and polyclonal plasma cells. NGS performed at the University of Washington confirmed P. sordellii infection. Neuropathologic Findings The gross and histologic examination showed mild hydrocephalus, right hippocampal atrophy, and anterior commissure–centric inflammation. Vascular congestion, arteriosclerosis with microthrombi, and oligodendrocyte loss were present without hemorrhage. Differential Diagnosis Hemophagocytic lymphohistiocytosis and CNS lymphoma were considered but ruled out microscopically. Conclusion This case highlights the importance of considering P. sordellii in CNS inflammatory lesions and demonstrates the utility of molecular diagnostics in negative cultures.