USMLE Q Bank Step 1- 198

A 23-year-old man presents to the emergency room complaining of massive watery diarrhea for 6 hours. He doesn’t have any vomiting or abdominal pain. Stool culture reveals a curved; gram negative rod which secretes an enterotoxin contains subunit A and a binding subunit B.

What is the most likely reason for this patient’s massive diarrhea?

A- Deficiency in the brush border enzymes

B- Decreased production of cAMP

C- Increased production of cAMP

D- Destruction of the absorptive epithelium

E- Increased motility of the small intestine

This patient most likely presents with cholera. Cholera enterotoxin causes secretory diarrhea, which means that excretion of water exceeds to a large extent its absorption. The enterotoxin indirectly stimulates adenylate cyclase to produce cAMP, which results in increased intracellular concentration of cyclic AMP which causes prolonged opening of the chloride channels leading to massive excretion of water.

The correct answer is C

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