Fatal case of amoebic encephalitis masquerading as herpes

Primary amoebic meningoencephalitis (PAM) is a rare, fulminating, hemorrhagic infection of the brain caused by Naegleria fowleri, a thermophilic, free-living amoeba. A 74-year male presented with sudden severe global headache and fever with features of anomic aphasia. Magnetic resonance imaging (MRI) suggested herpes encephalitis and acyclovir (IV) was started but the patient developed altered sensorium, agitation and progressive weakness of lower limbs with gradual truncal weakness. Repeat MRI showed increase in lesion size and edema with confluent blood areas. Dexamethasone showed significant improvement. Ten days after completion of acyclovir, there was recurrence of altered sensorium with seizures. Repeat MRI showed new lesions appearing. Excisional biopsy of brain confirmed N. fowleri. Amphotericin B and miltefosin was started but patient succumbed to his illness after 10 days. This is a first case of PAM in Nepal, involving elderly immune-competent male without environmental exposure to freshwater, mimicking as herpes encephalitis.