Definition of Carcinoid syndrome:

Carcinoid syndrome is a group of symptoms associated with carcinoid tumor (see bronchial adenoma).

Causes, incidence, and risk factors:

Carcinoid syndrome is the pattern of symptoms seen in people with carcinoid tumors. These tumors may occur in the small intestine, colon, bronchial tubes, or appendix.

Carcinoid tumors secrete excessive amounts of the hormone serotonin as well as other chemicals that cause the blood vessels to dilate (open). These tumors may also cause diarrhea and wheezing (asthma).

There are wide variations in the chemicals secreted by these tumors, and the symptoms depend on the mix of chemicals made by the particular tumor.

Normally, an amino acid called tryptophan is used by the body to make niacin and certain proteins, but in carcinoid syndrome, it forms serotonin instead. Most serotonin is changed by the body to 5-hydroxy indole acetic acid (5-HIAA).

The most bothersome symptoms include bright red facial flushing, diarrhea (which may be explosive and severe) and occasionally wheezing. A specific type of heart valve damage may occur, as well as other cardiac problems.

In children, carcinoid tumors usually occur in the appendix, and removal of the appendix usually results in a complete cure.