Alternative Names
Adenomatous Polyposis Coli; Adenomatous Polyposis of the Colon; Colon cancer, familial; Familial intestinal polyposis; Familial Multiple Polyposis; Familial multiple polyposis syndrome; Familial Polyposis Coli; Familial Polyposis Syndrome; FAP; Hereditary Polyposis Coli; MYH-associated polyposis; Polyposis coli
Symptoms & Characteristics
Familial adenomatous polyposis (FAP) is an inherited disorder characterized by colorectal cancer.
People with the classic type of familial adenomatous polyposis may begin to develop multiple noncancerous (benign) growths (polyps) in the colon as early as their teenage years. Unless the colon is removed, these polyps will become malignant (cancerous). The average age at which an individual develops colon cancer in classic familial adenomatous polyposis is 39 years.
Some people have a variant of the disorder, called attenuated familial adenomatous polyposis, in which polyp growth is delayed. The average age of colorectal cancer onset for attenuated familial adenomatous polyposis is 55 years.
In people with classic familial adenomatous polyposis, the number of polyps increases with age, and hundreds to thousands of polyps can develop in the colon. Also of particular significance are noncancerous growths called desmoid tumors. These fibrous tumors usually occur in the tissue covering the intestines and may be provoked by surgery to remove the colon. Desmoid tumors tend to recur after they are surgically removed. In both classic familial adenomatous polyposis and its attenuated variant, benign and malignant tumors are sometimes found in other places in the body, including the duodenum (a section of the small intestine), stomach, bones, skin, and other tissues. People who have colon polyps as well as growths outside the colon are sometimes described as having Gardner syndrome.
A milder type of familial adenomatous polyposis, called autosomal recessive familial adenomatous polyposis, has also been identified. People with the autosomal recessive type of this disorder have fewer polyps than those with the classic type. Fewer than 100 polyps typically develop, rather than hundreds or thousands. The autosomal recessive type of this disorder is caused by mutations in a different gene than the classic and attenuated types of familial adenomatous polyposis.
Treatment
Early diagnosis and routine surveillance may help to detect early stage colorectal cancer, when treatment is more likely to be effective.
How Common Is It?
The reported incidence of familial adenomatous polyposis varies from 1 in 7,000 to 1 in 22,000 individuals.
Genetics & Inheritance
Mutations in the APC gene cause both classic and attenuated familial adenomatous polyposis.
Familial adenomatous polyposis can have different inheritance patterns. When familial adenomatous polyposis results from mutations in the APC gene, it is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder. In most cases, an affected person has one parent with the condition.
When familial adenomatous polyposis results from mutations in the MUTYH gene, it is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. Most often, the parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but do not show signs and symptoms of the condition.
Genetic Testing
Cancer predisposition testing for FAP may be available through an in person genetic consultation for people who are considered at risk.
The decision to have genetic testing is personal and should always be discussed with trained medical professional. Use our find a genetic professional directory to locate a trained genetic professional in your area.
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