Symptoms of Carcinoid Syndrome
The primary symptoms of carcinoid syndrome include flushing (70% of cases), diarrhea (50-70% of cases), abdominal pain (40-70% of cases), and wheezing or bronchospasm (40% of cases). 1 These symptoms result from the release of hormones such as serotonin, tachykinins, and other vasoactive compounds directly into the systemic circulation, typically due to liver metastases.
Core Clinical Manifestations
Flushing
- Usually dry flushing without sweating (unlike menopausal flushing)
- Primarily affects the face and upper thorax
- May be accompanied by palpitations
- Can be triggered by alcohol, spicy foods, exercise, or emotional stress
Gastrointestinal Symptoms
- Diarrhea - often secretory and can be severe
- Intermittent abdominal pain (40% of cases)
- Nausea and vomiting may occur, particularly during flushing episodes 2
Respiratory Symptoms
- Wheezing (40% of cases)
- Bronchospasm
- Shortness of breath
- Lacrimation and rhinorrhea may occur during flushing episodes 1
Cardiac Manifestations
- Carcinoid heart disease - typically affects right-sided heart valves
- Usually occurs after the syndrome has been present for several years
- Characterized by fibrosis of tricuspid and pulmonary valves 1, 3
Less Common Symptoms
- Pellagra (niacin deficiency) due to tryptophan diversion to serotonin production 3
- Weight loss (reported in 30% of patients) 4
- Weakness or fatigue (23.5% of patients) 4
- Mental status changes including depression, anxiety, and cognitive impairment 5
- Skin manifestations including telangiectasias and venous dilatations
Carcinoid Crisis
Carcinoid crisis is a life-threatening complication characterized by:
- Profound flushing
- Severe bronchospasm
- Tachycardia
- Rapidly fluctuating blood pressure
- May include hypotension and cardiovascular collapse 1
This emergency is typically precipitated by:
- Anesthetic induction
- Surgical manipulation of tumor
- Invasive procedures like embolization or radiofrequency ablation
- Sometimes chemotherapy or radionuclide therapy 5
Clinical Patterns and Associations
- Carcinoid syndrome occurs in approximately 20% of midgut NETs (jejunum/ileum) 1
- Usually associated with liver metastases, allowing hormones to bypass hepatic metabolism
- Can occasionally occur without liver metastases if there is direct retroperitoneal involvement with venous drainage bypassing the liver 1
- Rarely associated with rectal NETs
- Bronchial carcinoids can present with atypical symptoms including cough (35%), hemoptysis (23%), and bronchial obstruction (41%) 1
Diagnostic Considerations
- Elevated urinary 5-HIAA (5-hydroxyindoleacetic acid, a serotonin metabolite) is the primary biochemical marker
- Serum chromogranin A is elevated in 75% of carcinoid tumors 1
- Symptoms may be misattributed to more common conditions like irritable bowel syndrome, leading to delayed diagnosis
Early recognition of these symptoms is critical for timely diagnosis and management of carcinoid syndrome, as the 5-year survival rate varies significantly depending on tumor location and extent of disease at diagnosis.