American Medical Association Family Medical Guide - American Medical Association [504]
Familial Polyposis
Familial polyposis (also called familial adenomatous polyposis or polyposis coli) is a relatively rare genetic disorder in which hundreds or thousands of growths—polyps or cysts—form in the colon (the longest part of the large intestine) and sometimes in the stomach or duodenum (the first part of the small intestine). The polyps usually begin to form during puberty; 95 percent of people with familial polyposis have polyps by age 35.
Most people with familial polyposis inherit the disorder from an affected parent. About 30 percent of cases result from a spontaneous change (mutation) in a gene that occurs during conception, which causes the disease to appear for the first time in a family. Because the abnormal gene is dominant (which means that it takes only one copy of the gene to cause the disease), each child of an affected person will have a 50 percent chance of inheriting the abnormal gene and having the disorder. Familial polyposis affects males and females equally and occurs in all racial and ethnic groups.
The polyps eventually become cancerous if they are not removed. However, familial polyposis is responsible for only 1 percent of cases of colon cancer (see next page). The average age at which colon cancer develops in people with untreated familial polyposis is 39 years. If you have familial polyposis, a genetic counselor (see page 952) can help you understand the disorder and evaluate your risk of passing it on to your children.
Symptoms
Although the polyps begin to grow at puberty, most adolescents with familial polyposis have no symptoms. As the disease progresses, symptoms may include blood and mucus in the stool, bleeding from the rectum, a change in bowel habits, diarrhea, abdominal pain, or weight loss. People with some types of familial polyposis tend to produce extra tissue in the form of cysts or bony growths in other parts of the body, including the skin, bones, eyes, thyroid gland, and abdomen.
Diagnosis
To diagnose familial polyposis, your doctor will ask you if anyone in your family has ever been diagnosed with intestinal polyps or colon cancer. He or she will recommend a genetic test that detects the gene mutation that causes familial polyposis. Your doctor will probably perform a procedure called colonoscopy (see page 767) to examine the inside of your colon. He or she may also order a barium X-ray (see page 767) of your colon.
Treatment
Removing the entire colon is the only treatment for familial polyposis because the polyps are too numerous to be removed individually. In some cases, the rectum is also removed. The surgeon may create a temporary or permanent opening on the outside of the abdomen called an ileostomy (see next page) to replace the rectum and through which stool can pass.
Colon Cancer
Cancer of the large intestine is usually called colon cancer or colorectal cancer. It occurs most often in the lowest part of the large intestine. Colon cancer is the third most common cancer (after lung cancer and breast cancer). The cause of colon cancer is unknown, but researchers think that a diet high in animal fat (especially from red meat) and low in fiber may play a role. Smoking cigarettes has been linked to colon cancer. Genes also have an influence—having a family history of colon cancer increases your risk. Having ulcerative colitis (see page 764) also increases your risk—about 1 of 20 people who have had ulcerative colitis for more than 10 years eventually develops colon cancer. Having adenomatous intestinal polyps (see page 773) that are not detected and removed also increases the risk of colon cancer. Men and women are equally susceptible. Colon cancer is most prevalent in people over 40, and the incidence increases with age.
As the cancerous cells multiply, the normally smooth