Spot diagnosis

A 60-year-old woman presents with an eight-month history of colicky abdominal pain, diarrhoea and occasional flushing of the face and chest.

Examination reveals bilateral wheezing and a distended, non-tender abdomen.

5-hydroxyindoleacetic acid levels are elevated and a CT scan demonstrates a hypervascular, plaque-like mass in the terminal ileum, with soft-tissue spokes radiating into the mesenteric fat.

Which of the following neurotransmitters is responsible for this patient’s symptoms?

  • Dopamine
  • Serotonin
  • Norepinephrine
  • GABA

Answer: This patient’s presentation is suggestive of carcinoid syndrome, secondary to a carcinoid tumour in the small intestine. The syndrome, characterised by cutaneous flushing and diarrhoea, is caused by the serotonin secreted by the tumour. Systemic symptoms are most common in patients with hepatic metastases.

When serotonin is produced in the liver, it lacks first-pass metabolism and can produce the symptoms seen in this case.

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