Introduction Demographics Causes Clinical features Complications Diagnosis Differential diagnoses Treatment Outcome
Carcinoid syndrome is characterised by episodic cutaneous flushing, diarrhoea, and wheezing.
Carcinoid syndrome is the result of a combination of peptides and amines secreted by advanced neuroendocrine tumours (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. The incidence is 1–2 per 100,000 people annually. They can occur in people with multiple endocrine neoplasia type 1 and Peutz-Jeghers syndromes.
Carcinoid symptoms are more common in those with bowel tumours, particularly when they have spread to the liver.
Neuroendocrine tumours can secrete bioactive amines into the bloodstream, causing symptoms of carcinoid syndrome. The most common amines and peptides are:
The main cutaneous feature of carcinoid syndrome is flushing, which occurs in 75% of cases. This is caused by transient dilation of blood vessels.
Patients with neuroendocrine tumours may have deficiency in niacin. This manifests as a triad of dermatitis, dementia, and diarrhoea (pellagra). Clinically, patients present with erythematous skin with superficial scaling in areas exposed to sunlight.
Flushing could be spontaneous or triggered by:
Carcinoid syndrome may also cause other symptoms such as weight loss, low blood pressure, and abdominal pain.
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 valve fibrosis, nutritional deficiencies (deficiency of niacin leading to pellagra), and neuropsychiatric manifestations.
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 by CT and MR imaging, as well as specific radioisotope scanning (MIBG and octreotide scans).
Carcinoid syndrome is a paraneoplastic phenomenon, and therefore treating the underlying neuroendocrine tumour is key.
Carcinoid crisis can be treated with intravenous octreotide, intravenous hydrocortisone, and/or intravenous chlorpheniramine.
If all of the carcinoid tumours can be resected, then prognosis is excellent. If carcinoids have metastasised to the liver or other organs, and there is evidence of progressive, recurring or relapsing disease, then the prognosis is more guarded.
