Abstract
BACKGROUND: Primary amoebic meningoencephalitis (PAM) is caused by Naegleria fowleri, a rare but highly fatal central nervous system infection with a mortality rate exceeding 95%. Early diagnosis is challenging due to the close similarity of its clinical manifestations and cerebrospinal fluid (CSF) findings to those of acute bacterial meningitis. Metagenomic next-generation sequencing (mNGS) has become a vital tool for identifying rare or unexpected pathogens. CASE PRESENTATION: A previously healthy 6-year-old girl was admitted with fever, vomiting, and headache of 1 day's duration. Six days before symptom onset, she had played in natural freshwater bodies. After admission, she developed persistent high fever and rapidly progressive altered mental status, followed by two episodes of generalized tonic-clonic seizures, hemoptysis, acute respiratory failure, and circulatory shock. Initial cranial magnetic resonance imaging showed no abnormalities. CSF analysis revealed marked inflammatory changes: a white blood cell count of 3,072 × 10(6)/L, markedly elevated protein (3,667.6 mg/L), and significantly decreased glucose (0.08 mmol/L). Despite administration of broad-spectrum antibiotics, glucocorticoids, osmotherapy, and comprehensive intensive care unit management, the patient died approximately 11 h after admission following three cardiac arrests. Two days postmortem, CSF mNGS confirmed infection with Naegleria fowleri (copy number 3 × 10(5) copies/mL), establishing the diagnosis of PAM. CONCLUSIONS: This pediatric case serves as a warning that PAM should be considered in children with a history of freshwater exposure and rapidly progressive meningoencephalitis, even when early imaging is normal and CSF findings resemble bacterial meningitis. Early lumbar puncture, rapid molecular diagnostics, and heightened clinician vigilance are critical for the timely initiation of targeted therapy.