Question:medium
A 35-year-old heterosexual patient diagnosed with HIV had a history of chronic watery diarrhea. A colonoscopic biopsy is shown below. The most probable diagnosis is?
A 35-year-old heterosexual patient diagnosed with HIV had a history of chronic watery diarrhea. A colonoscopic biopsy is shown below. The most probable diagnosis is?
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Tiny round organisms hugging the apical surface of enterocytes like blue beads in an HIV patient.
Updated On: Jun 23, 2026
- Giardia
- CMV
- Microspora
- Cryptosporidium
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The Correct Option is D
Solution and Explanation
Clinical pearl: in an HIV patient with profuse chronic watery (non-bloody) diarrhea, think Cryptosporidium first. It is one of the most common AIDS-defining causes of intractable diarrhea once CD4 counts fall.
The biopsy clinches it. Cryptosporidium oocysts appear as small basophilic round structures, roughly $2$ to $5$ $\mu$m, lined up along the apical (brush border) surface of enterocytes, looking like beads stuck to the cell edge while remaining intracellular yet extracytoplasmic. Giemsa highlights them.
Eliminate the others: CMV colitis gives bloody diarrhea with owl-eye intranuclear inclusions, Giardia trophozoites float in the duodenal lumen as pear-shaped flagellates, and microsporidia need modified trichrome to be seen. None reproduce the apical blue-bead look, so the answer is option (d), Cryptosporidium.
The biopsy clinches it. Cryptosporidium oocysts appear as small basophilic round structures, roughly $2$ to $5$ $\mu$m, lined up along the apical (brush border) surface of enterocytes, looking like beads stuck to the cell edge while remaining intracellular yet extracytoplasmic. Giemsa highlights them.
Eliminate the others: CMV colitis gives bloody diarrhea with owl-eye intranuclear inclusions, Giardia trophozoites float in the duodenal lumen as pear-shaped flagellates, and microsporidia need modified trichrome to be seen. None reproduce the apical blue-bead look, so the answer is option (d), Cryptosporidium.
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