Diagnostic Findings [Last Modified: ]
Blastocystis hominis infection
[Blastocystis hominis]
Causal Agent Life Cycle Geographic Distribution Clinical Features Laboratory Diagnosis Treatment

Microscopy
Blastocystis hominis appear as spherical to oval cyst-like structures.  They can vary widely in size (5 to 30 µm; usual range 8 to 10 µm), and typically consist of a central body, or "vacuole" surrounded by a thin rim of cytoplasm containing up to six nuclei.

Blastocystis hominis, trichrome stain Blastocystis hominis, trichrome stain
A B

Blastocystis hominis, trichrome stain Blastocystis hominis, trichrome stain
C  D

A, B, C, D: Blastocystis hominis cyst-like forms stained in trichrome.  The sizes vary from 4 µm (A) to 10 µm (F).  The vacuoles stain variably from red to blue.  Specimens in Figures A, B, and C were contributed by Dr. Ray Kaplan, SmithKline Beecham Diagnostic Laboratories, Atlanta, GA.

Blastocystis hominis, iodine stain Blastocystis hominis, iodine stain
E F

E, F: Blastocystis hominis cyst-like forms stained with iodine.

Blastocystis hominis, unstained cyst-like form
G

G: An unstained Blastocystis hominis cyst-like form.
Back Top