Case #181 – June, 2006

A patient was admitted to a hospital with a one-day history of fever and persistent headache on the right side. Approximately 10 days prior to the onset of symptoms, the individual swam in a small swimming hole, associated with a river. Two days after admission the patient developed a stiff neck, becoming progressively sleepy. The patient became lethargic and unresponsive to pain stimulation, and treatment with acyclovir and manitol was started. A computed tomography (CT) was performed and showed a lesion in the right frontal lobe and diffuse cerebral edema. The patient was pronounced dead 6 days after the onset of symptoms. Figures A and B are from hematoxylin and eosin (H & E) stained brain tissue specimens sent to CDC for confirmatory diagnosis. Objects shown Figure B ranged from 10 to 12 µm in diameter. What is your diagnosis? Based on what criteria? Which additional diagnostic test would you recommend to achieve a final diagnosis?

Figure A

Figure B

This was a case of primary amebic meningoencephalitis (PAM) caused by Naegleria fowleri. Diagnostic features were:

the presence of trophozoites, with large nuclei, conspicuous karyosomes, and vacuolated cytoplasm.
trophozoites that measured 10 to 12 µm in diameter.

Indirect immunofluorescence analysis demonstrated a positive reaction with anti-N. fowleri serum (Figure C below). Along with morphology and immunological testing, clinical features were compatible with PAM.

Figure A