Granulomatous amoebic encephalitis

Did You Know?

• A brain biopsy reveals infection by pathogenic amoebas, showing general inflammation and sparse granules with infiltrates of amoebic cysts and/or trophozoites on microscopic examination.
• The condition is difficult to diagnose because it is a rare disease.

Signs and symptoms

The illness begins slowly with headache, nausea, dizziness, irritability, and low-grade fever. Central nervous system signs depend on the infected brain region and may include seizures, focal neurologic deficits, double vision, cranial nerve palsies, ataxia, confusion, and personality changes. Behavioral changes are an important sign. The presentation can mimic glioma or other brain diseases, delaying diagnosis. Symptoms arise from inflammatory necrosis of brain tissue caused by compounds released by the organisms.

Treatment

Antifungals such as ketoconazole, miconazole, 5-flucytosine, and pentamidine show in vitro effectiveness against Acanthamoeba. A regimen of cloxacillin, ceftriaxone, and amphotericin B was not effective. Nitroxoline has demonstrated in vitro activity; a man treated with it at UCSF Medical Center in 2021 survived and recovered, and a pediatric patient also survived after nitroxoline treatment. Other reported treatments include azithromycin, pentamidine, itraconazole, and flucytosine.

Prognosis

Even with treatment, Acanthamoeba central nervous system infection is often fatal, with a mortality rate approaching 90%. Very few survivors are recorded, and almost all have permanent neurocognitive deficits. Prognosis depends on timing of diagnosis, strain virulence and sensitivity, and most crucially the patient's immune status.