A Novel Balamuthia Lineage Causing Fatal Granulomatous Amoebic Encephalitis in an Immunocompetent Infant.

Publication date: Sep 17, 2025

To characterize a genetically distinct Balamuthia lineage causing fatal granulomatous amoebic encephalitis (GAE) in a 10-month-old infant and highlight diagnostic challenges compounded by SARS-COV-2 infection comorbidity. Case report of a 10-month-old male with GAE. Metagenomic next-generation sequencing (mNGS) and PCR sequencing of 18S/12S rRNA genes from brain biopsy tissue were performed. Phylogenetic analysis was conducted to identify the genetic characteristics of the pathogen. The patient presented with recurrent fever, seizures, and rapidly progressive neurological deterioration. He had documented SARS-CoV-2 infection two weeks prior to symptom onset. The mNGS of biopsy tissue identified Balamuthia infection. Genetic analysis revealed 18S rRNA similarity of 95. 33% and mitochondrial 12S rRNA similarity of 85. 49% versus known species. Phylogenetic trees confirmed a distinct clade, suggesting a potential novel species. Despite aggressive treatment, the patient died after 13 days of hospitalization. This case highlights the challenges in diagnosing and managing GAE, particularly in pediatric patients with atypical presentations. The discovery of a genetically distinct Balamuthia strain indicates the importance of global surveillance for emerging pathogens. Clinicians should consider Balamuthia as a potential cause of encephalitis in children with unexplained neurological symptoms, even in non-endemic regions.

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