Question:
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
Step 1: An HIV patient with chronic watery diarrhea is the classic setting for an opportunistic protozoal gut infection.
Step 2: The biopsy shows small (2 to 5 \(\mu\)m) basophilic round bodies sitting along the apical brush border of the enterocytes, appearing to protrude from the cell surface (the so-called blue beads), within the cell membrane. This intracellular but extracytoplasmic location is characteristic of Cryptosporidium.
Step 3: Supporting features are villous atrophy, crypt hyperplasia and a mixed inflammatory infiltrate in the lamina propria. The organisms highlight with Giemsa. CMV would show large cells with intranuclear owl-eye inclusions, Giardia shows pear-shaped trophozoites in the lumen, and microsporidia are tiny spores best seen on special stains, none matching the apical bead appearance.
Answer: Cryptosporidium.
Ref: Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases, 8e.
Step 2: The biopsy shows small (2 to 5 \(\mu\)m) basophilic round bodies sitting along the apical brush border of the enterocytes, appearing to protrude from the cell surface (the so-called blue beads), within the cell membrane. This intracellular but extracytoplasmic location is characteristic of Cryptosporidium.
Step 3: Supporting features are villous atrophy, crypt hyperplasia and a mixed inflammatory infiltrate in the lamina propria. The organisms highlight with Giemsa. CMV would show large cells with intranuclear owl-eye inclusions, Giardia shows pear-shaped trophozoites in the lumen, and microsporidia are tiny spores best seen on special stains, none matching the apical bead appearance.
Answer: Cryptosporidium.
Ref: Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases, 8e.
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