A 50-year-old woman comes to the physician due to periodic reddening of her skin that is starting to become bothersome. The redness involves mainly her face and neck and is accompanied by mild warmth. The episodes initially lasted only a few minutes, but now they sometimes exceed 20 minutes. The patient has also had persistent watery diarrhea and associated abdominal cramping for the last several months. Physical examination shows several, purple vascular lesions surrounding her nose. Urinary excretion of 5-hydroxyindoleacetic acid (5-HIAA) over 24 hours is increased. Abdominal imaging shows a tumor in the small intestine. Which of the following is most likely responsible for this patient's condition?

Question

A 50-year-old woman comes to the physician due to periodic reddening of her skin that is starting to become bothersome.  The redness involves mainly her face and neck and is accompanied by mild warmth.  The episodes initially lasted only a few minutes, but now they sometimes exceed 20 minutes.  The patient has also had persistent watery diarrhea and associated abdominal cramping for the last several months.  Physical examination shows several, purple vascular lesions surrounding her nose.  Urinary excretion of 5-hydroxyindoleacetic acid (5-HIAA) over 24 hours is increased.  Abdominal imaging shows a tumor in the small intestine.  Which of the following is most likely responsible for this patient's condition?

Quizplus · Accepted Answer

11ec160b_3ad7_b857_9249_3737ea888366_MD0001_00 Carcinoid tumors most frequently arise from the enterochromaffin (endocrine) cells of the intestinal mucosa. These cells produce a number of vasoactive substances, such as serotonin (5-HT), bradykinin, and prostaglandins. When the tumor is confined to the intestine, these secretory products are metabolized by the liver and patients do not develop carcinoid syndrome. In contrast, if intestinal carcinoid metastasizes to the liver, these vasoactive substances bypass the liver and enter the systemic circulation, resulting in carcinoid syndrome. Extraintestinal carcinoid tumors (eg, bronchial carcinoid) can cause carcinoid syndrome without metastasizing as the vasoactive substances are secreted directly into systemic circulation (again bypassing hepatic metabolism). Increased level of the serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA) in a 24-hour urine sample is the most useful initial test for confirming carcinoid syndrome. (Choices A, D, and E) Adenocarcinoma, lymphoma, and secretory leiomyoma would not result in carcinoid syndrome or elevated urinary 5-HIAA levels. (Choice B) The vasoactive substances secreted by a localized intestinal carcinoid tumor are metabolized by the liver via first-pass metabolism, preventing the development of carcinoid syndrome. Extraintestinal metastasis of intestinal carcinoid tumors is required to produce carcinoid symptoms. Educational objective: Carcinoid tumors confined to the intestine do not cause carcinoid syndrome as their secretory products are metabolized by the liver before entering the systemic circulation. In contrast, intestinal carcinoids that metastasize to the liver and extraintestinal (eg, bronchial) carcinoids release vasoactive substances that avoid first-pass metabolism, resulting in carcinoid syndrome (eg, flushing, diarrhea, bronchospasm).

A 50-Year-Old Woman Comes to the Physician Due to Periodic