Spontaneous granulomatous amebic encephalitis: report of four cases from Thailand.

Granulomatous amebic encephalitis (GAE), or meningoencephalitis caused by Acanthamoeba sp and leptomyxid amebae are uncommon CNS infections that usually occur in an immunocompromised host. From 1990 to 1992, 4 patients with GAE were treated at Siriraj Hospital, Bangkok. One case was diagnosed antemortem, from a brain biopsy. The other three cases were diagnosed as GAE postmortem. Pathological findings included acute and subacute granulomatous inflammation with extensive cerebral necrosis, angiitis, fibrinoid necrosis and fibrin thrombi. One patient had a chronic skin ulcer in which free-living amebic trophozoites were found. No visceral involvement was observed. All patients developed "spontaneous" GAE, but we suspect an undiagnosed abnormality in cell mediated immunity or a deficient humoral immune response.