A rare, inherited disorder in which many polyps (abnormal growths of tissue) form on the inner walls of the colon and rectum. Other signs and symptoms of Gardner syndrome include dental problems and benign (not cancer) growths or tumors in the bone, soft tissue, skin, adrenal glands, stomach, and small intestine. People with Gardner syndrome have a very high risk of developing colorectal cancer at an early age. They are also at risk of developing cancers of the small bowel, stomach, pancreas, thyroid, central nervous system, liver, bile ducts, and adrenal gland. Gardner syndrome is caused by a mutation (change) in a gene called APC. It is a type of familial adenomatous polyposis and a type of autosomal dominant genetic disease.