Fatal primary amoebic meningoencephalitis in a Norwegian tourist returning from Thailand

INTRODUCTION: Primary amoebic meningoencephalitis (PAM) is a rare disease caused by the free-living amoeba Naegleria fowleri. Infection occurs by insufflation of water containing amoebae into the nasal cavity, and is usually associated with bathing in freshwater. Nasal irrigation is a more rarely reported route of infection. CASE PRESENTATION: A fatal case of PAM in a previously healthy Norwegian woman, acquired during a holiday trip to Thailand, is described. Clinical findings were consistent with rapidly progressing meningoencephalitis. The cause of infection was discovered by chance, owing to the unexpected detection of N. fowleri DNA by a PCR assay targeting fungi. A conclusive diagnosis was established based on sequencing of N. fowleri DNA from brain biopsies, supported by histopathological findings. Nasal irrigation using contaminated tap water is suspected as the source of infection. CONCLUSION: The clinical presentation of PAM is very similar to severe bacterial meningitis. This case is a reminder that when standard investigations fail to identify a cause of infection in severe meningoencephalitis, it is of crucial importance to continue a broad search for a conclusive diagnosis. PAM should be considered as a diagnosis in patients with symptoms of severe meningoencephalitis returning from endemic areas.