What is carcinoidsyndrome?
Carcinoid syndrome is characterised by episodiccutaneousflushing, diarrhoea, and wheezing.
Carcinoid syndrome is the result of a combination ofpeptidesand amines secreted by advancedneuroendocrinetumours(NETs) into the bloodstream.
Carcinoid syndrome affects up to 19% of people with neuroendocrine tumours, which can be present in the gut, pancreas, lung, kidney, ovaries, and testes. They are rare in children. Theincidenceis 1–2 per 100,000 people annually. They can occur in people with multipleendocrineneoplasiatype 1 andPeutz-Jegherssyndromes.
Carcinoid symptoms are more common in those with bowel tumours, particularly when they have spread to the liver.
What causes carcinoid syndrome?
Neuroendocrine tumours can secrete bioactive amines into the bloodstream, causing symptoms of carcinoid syndrome. The most common amines and peptides are:
- Serotonin (keymoleculeassociated with carcinoid syndrome)
What are the clinical features of carcinoid syndrome?
The main cutaneous feature of carcinoid syndrome is flushing, which occurs in 75% of cases. This is caused bytransientdilation ofblood vessels.
- Flushing (red brown or bright red colour) affects the face, head, neck, chest, and epigastric areas.
- It may last for several minutes to several hours (particularly in the later stages of the disease).
- The skin may be diffusely affected or mottled, with or without accompanyingoedema.
- Recurrentflushing may lead to long-lasting skin changes, includingtelangiectasiaand plethora (persistentredness).
Patients with neuroendocrine tumours may have deficiency in niacin. This manifests as a triad ofdermatitis, dementia, and diarrhoea (pellagra). Clinically, patients present witherythematousskin with superficialscalingin areas exposed to sunlight.
Flushing could be spontaneous or triggered by:
- Psychological stress
- Physical stress
- Food items which are either spicy or rich in amines (eg, chocolate, kiwi, banana, avocados)
- Medications (eg, catecholamines, calcium, and pentagastrin).
Carcinoid syndrome may also cause other symptoms such as weight loss, low blood pressure, and abdominal pain.
What are the complications of carcinoid syndrome?
Carcinoid syndrome can cause carcinoid crisis, which involves cutaneous flushing,hypotension,tachycardia/arrhythmias,bronchospasm, and/or sometimes hyperthermia.
Patients with carcinoid syndrome may experience long-term complications such as carcinoid heart disease, causing valvefibrosis, nutritional deficiencies (deficiency of niacin leading to pellagra), and neuropsychiatricmanifestations.
How is carcinoid syndrome diagnosed?
Carcinoid syndrome may be suspected clinically, and confirmed by finding an elevated 24-hour urine 5-hydroxyindoleacetic acid (5-HIAA), which is an indirect marker of serotonin production. The extent of tumours can be identified byCTand MR imaging, as well as specific radioisotope scanning (MIBG and octreotide scans).
What is thedifferential diagnosisfor carcinoid syndrome?
- Irritable bowel syndrome
- Celiac disease
- Acutepseudo-obstruction of the bowel
What is the treatment for carcinoid syndrome?
Carcinoid syndrome is aparaneoplasticphenomenon, and therefore treating the underlying neuroendocrinetumouris key.
- Surgicalresectionof theprimarytumour as well asnodaland livermetastasesreduces the tumour burden.
- Tumourchemotherapymay help advancedmetastaticdisease as can radiopharmaceuticals.
- Symptomatic treatment with medications such as somatostatinreceptoranalogues(eg, octreotide) and/or interferon alfa may be used for symptoms associated with amine secretion.
Carcinoid crisis can be treated with intravenous octreotide, intravenous hydrocortisone, and/or intravenous chlorpheniramine.
What is the outcome for carcinoid syndrome?
If all of the carcinoid tumours can be resected, thenprognosisis excellent. If carcinoids have metastasised to the liver or other organs, and there is evidence ofprogressive, recurring or relapsing disease, then the prognosis is more guarded.