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Carcinoid syndrome 

Carcinoid syndrome
Carcinoid syndrome

B. Khoo

, T.M. Tan

, and S.R. Bloom

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date: 02 March 2021

Carcinoid syndrome is a paraneoplastic syndrome caused by the release of 5-hydroxytryptamine (5-HT or serotonin) and other vasoactive substances from neuroendocrine tumours (NETs), typically those arising from the duodenum, jejunum, ileum, and also from bronchial NETs. Characteristic clinical features, which typically arise when tumours have metastasized to the liver, are flushing and secretory diarrhoea, and occasionally wheezing. Carcinoid crisis is an acute and life-threatening manifestation with sustained flushing, hyperdynamic shock, and acute kidney injury. Carcinoid heart disease typically manifests in the right side of the heart with valvular insufficiency and heart failure. Diagnosis is made by a combination of the characteristic clinical syndrome, biochemical markers such as 5-hydroxyindoleacetic acid (a metabolite of 5-HT), histopathological examination of tissue from tumour deposits, and imaging with conventional cross-sectional modalities as well as somatostatin receptor scintigraphy. Treatment is most often directed at control of symptoms, with the standard of care for control of the carcinoid syndrome being a somatostatin analogue. Symptomatic therapies are used to palliate diarrhoea. Niacin supplements should be given to forestall the development of pellagra. Multiple modalities for treatment of NETs exist, which should be directed by a multidisciplinary team. Their general prognosis is good with median overall survival of 9.3 years, but the presence of carcinoid syndrome cuts this to 5.0 years, and less in the presence of heart disease.

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