Cerebral cavernous malformation with secondary bacterial infection: illustrative case.

backgroundSecondary infection of cerebral cavernous malformations (CCMs) is exceedingly rare, with only a few cases reported in the literature. While CCMs are typically sporadic or familial vascular malformations, there is growing evidence that local or systemic infections may influence their pathogenesis or complicate existing lesions. OBSERVATIONS: The authors report the case of a 5-year-old boy who presented with clinical features of meningitis and was found to have a right frontal multilobulated cystic mass with appearances concerning for abscess or neoplasm. The patient underwent resection, which confirmed a cavernous malformation with superimposed abscess formation. Cultures identified Streptococcus pneumoniae, and subsequent investigations revealed multiple CCMs as well as a pathogenic KRIT1 gene mutation. The child made a complete recovery with targeted antibiotic therapy. LESSONS: This is the first documented case of a CCM secondarily infected by S. pneumoniae. It emphasizes the importance of considering infection in patients with known or suspected CCMs presenting with systemic or intracranial infection, particularly when imaging is atypical. Furthermore, this case provides insight into CCM biology: in KRIT1 mutations, impaired endothelial integrity may predispose lesions to inflammatory and infectious insults, supporting the concept that cavernomas are dynamic vascular malformations shaped by genetic, immune, and infectious interactions. https://thejns.org/doi/10.3171/CASE25628.