Hemorrhagic brain abscess mimicking an intracranial neoplasm in invasive Klebsiella pneumoniae syndrome: illustrative case.

BACKGROUND: Brain abscess rarely presents with hemorrhagic transformation. Invasive Klebsiella pneumoniae syndrome (IKPS) is characterized by hematogenous dissemination from a primary hepatic focus, causing metastatic infections in various organs. The authors report a rare case of hemorrhagic brain abscess mimicking an intracranial neoplasm in the setting of IKPS managed with stereotactic drainage. OBSERVATIONS: A 56-year-old male with a history of intra-abdominal surgery presented with progressive right-sided hemiparesis. CT performed at the referring hospital revealed a ring-enhancing lesion in the left basal ganglia consistent with a brain abscess. Repeat CT performed at the authors' institution showed a new intracavitary hemorrhage. Stereotactic aspiration yielded blood-tinged purulent material that grew K. pneumoniae; blood cultures exhibited negative results. Systemic workup confirmed disseminated IKPS with liver, spine, psoas muscle, and urinary tract involvement. Two stereotactic drainage procedures were required, with significant reduction of the abscess following the second procedure. LESSONS: Hemorrhagic brain abscess can radiologically mimic an intracranial neoplasm, particularly when hemorrhage complicates typical imaging features. Disseminated K. pneumoniae infection may occur despite negative blood cultures. Stereotactic drainage is safe and effective, and serial imaging is crucial for detecting reaccumulation and guiding repeat intervention. https://thejns.org/doi/10.3171/CASE26593.