Updated: 3/24/2020

Carcinoid Syndrome

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Snapshot
  • A 42-year-old man presents to the clinic with complaint of watery diarrhea for the past four months. He states that he has not seen any blood in his stool. Upon further questioning, he states that he has also experienced intermittent abdominal pain and asthma attacks. On physical examination, the patient's face and neck appears as seen in the image.
Introduction
  • Overview
    • carcinoid syndrome is a rare syndrome that is caused by the metastasis of carcinoid tumors that secrete high levels of serotonin (5-HT)
      • treatment is usually with surgical resection or octreotide
  • Epidemiology
    • incidence
      • rare, 1-2 cases per 100,000 individuals
    • demographics
      • most frequently in patients 50-70 years
  • Pathophysiology
    • metastasis of carcinoid tumors that produce serotonin
      • carcinoid tumors most commonly located in the ileum and appendix (90%)
        • carcinoid tumors arise from neuroendocrine cells
        • carcinoid syndrome is observed if there is metastasis of the tumor outside of the GI system
          • if there is metastasis to the liver, first-pass metabolism of secreted serotonin is disrupted and hormones reach systemic circulation
  • Associated conditions
    • medical conditions
      • pellagra caused by niacin (vitamin B3) deficiency
        • all tryptophan is consumed in making excess 5-HT
Presentation
  • Symptoms
    • common symptoms
      • cutaneous flushing
      • recurrent diarrhea
        • ↑ bowel motility
      • abdominal cramps
      • asthma-like wheezing
  • Physical exam
    • erythema
    • pellagra skin lesions
    • wheezing
    • hepatomegaly from metastases
    • pulmonary systolic and diastolic heart murmur
      • cardiac involvement causes carcinoid heart disease
        • primarily occurs on right side of the heart
          • tricuspid valve most commonly affected
Imaging
  • CT
    • indication
      • localize the primary tumor
      • assess extent of tumor spread and metastases
  • In-111 octreotide scan
    • indication
      • localize the primary carcinoid tumor and recurrences
Studies
  • Labs
    • measurement of urinary excretion of 5-HIAA
      • best initial test
      • urinary excretion of 5-HIAA ≥ 25mg/day is diagnostic
        • 5-HT is degraded to 5-HIAA and excreted in the urine
Differential
  • VIPoma
    • key distinguishing factor
      • presents with WDHA syndrome
        • Watery Diarrhea
        • Hypokalemia
        • Achlorhydria
      • may present with flushing similar to carcinoid syndrome but no wheezing or right-sided heart murmurs are present
Treatment
  • Surgical
    • surgical resection of tumor
      • indications
        • first-line treatment
        • reduces tumor mass and achieves symptom remission
  • Medical 
    • octreotide or other somatostatin analog
      • indications
        • alleviates flushing and diarrhea
Complications
  • Carcinoid heart disease
    • incidence
      • up to 50% of patients with carcinoid syndrome
    • risk factors
      • higher urinary levels of 5-HIAA associated with greater risk of progression of carcinoid heart disease
    • treatment
      • somatostatin analogs

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