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Carcinoid syndrome — USMLE Step 3 MCQ

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ModerateAmbulatory Medicine / Primary CareCarcinoid syndromeUSMLE Step 3

A 39-year-old woman has episodic flushing, watery diarrhea, and wheezing. She has a systolic murmur that increases with inspiration. CT abdomen shows multiple liver lesions and a small ileal mass. Urine 5-HIAA is elevated. Which of the following is the most likely explanation for this patient's findings?

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Correct answer: B — Serotonin secretion from metastatic neuroendocrine tumor

Carcinoid syndrome usually occurs when serotonin-secreting neuroendocrine tumors metastasize to the liver, bypassing first-pass hepatic metabolism and causing flushing, diarrhea, bronchospasm, and right-sided valvular disease.

Reference: NCCN neuroendocrine tumor guidance