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[Acanthamoeba spp.] [Balamuthia mandrillaris] [Naegleria fowleri] [Sappinia spp.]

The cysts of Acanthamoeba spp. are typically 10-25 µm in diameter.  The cysts have two walls: a wrinkled fibrous outer wall (exocyst) and an inner wall (endocyst) that may be hexagonal, spherical, star-shaped or polygonal.  Cysts contain only one nucleus with a large karyosome.  Cysts may be found in the brain, eyes, skin, lungs and other organs.

A	B

A, B: Cysts of Acanthamoeba sp. from brain tissue, stained with hematoxylin and eosin (H&E).

C

C: Cysts of Acanthamoeba sp. (green arrows) in tissue, stained with H&E.