The carcinoid syndrome is characterised by:
- paroxysmal flushing - for example, following coffee, alcohol, certain foods and drugs
- bronchoconstrictive episodes, similar to asthma
- right-sided heart failure
- episodes of explosive watery diarrhoea
- abdominal pain
- pellagra-like lesions of the skin and oral mucosa
Gastrointestinal carcinoid tumours may present with bowel obstruction.
Examination may reveal an enlarged liver or abdominal mass.
The cutaneous lesions result from the increased conversion of tryptophan to serotonin and consequently, a reduction in the amount available for incorporation into nicotonic acid.
Cardiac failure is a consequence of plaque-like thickenings superimposed on the endocardium and valvular cusps, mostly on the outflow tract of the right ventricle. Left-sided lesions are rare, a finding attributed to inactivation of serotonin during passage through the lungs by the monoamine oxidase found in the pulmonary vascular endothelium.
Notes (1):
- fewer than 10% of patients with carcinoid suffer from classical carcinoid syndrome of flushing, hypotension, diarrhoea, wheezing and heart disease- these symptoms seem to be related directly to serotonin levels
- development of carcinoid heart disease appears to be linked to high serotonin levels
- carcinoid tumours deriving from the gastric histamine-secreting enterochromaffin-like cells produce an ‘atypical’ carcinoid syndrome
- these tumours have low serotonin levels and frequently secrete the serotonin precursor 5-hydroxytryptophan (5- HTP)
- 5-HTP producing carcinoid tumours (foregut carcinoids) may be associated with 'atypical carcinoid' symptoms with more intense and protracted purplish fushing. The flushing associated with foregut carcinoids may affect the limbs as well as the upper trunk; also there are frequently telangiectasia
Reference:
- Endocr Relat Cancer. 2004 Mar;11(1):1-18.