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MUTYH-associated polyposis (MAP) also is called familial adenomatous polyposis type 2 (FAP2).

W?hat is MUTYH-associated polyposis (MAP)?

MUTYH-associated polyposis (MAP) is an inherited condition that causes abnormal growths, called polyps, in the gastrointestinal (GI) tract. Having polyps can increase your risk of cancer.

Signs and symptoms of MUTYH-associated polyposis (MAP)

At first, colon polyps may not cause any symptoms. As more polyps grow or as they get larger, symptoms can develop. These include:

• Blood in the stool
• , such as diarrhea, constipation, or thin stools
• Trouble having bowel movements when a large polyp blocks the intestines, called a gastrointestinal obstruction
• Belly cramps
• Weight loss that is not explained by changes in diet or exercise
•  (tiredness) or low energy
•  (low red blood cells from a bleeding polyp)

People with MAP can also have:

• Thyroid nodules (lumps on the thyroid gland)
• Tumors on the adrenal gland
• Cysts in the jawbone
• Changes in the retina, part of the eye, called CHRPE (congenital hypertrophy of the retinal pigment epithelium)

Other medical conditions can also cause these symptoms so they should be checked by a doctor.

What causes MUTYH-associated polyposis (MAP)?

Changes in the MUTYH gene cause MUTYH-associated polyposis. The MUTYH gene repairs DNA. This means the normal MUTYH gene corrects mistakes made when cells divide and grow. When mistakes in the DNA or damage are not fixed before the cells divide, the mistake is copied to other cells. When these mistakes pile up, cells grow unchecked, and cancers can develop.

Each person has two copies of the MUTYH gene in their DNA. For a person to develop MAP, both copies must be mutated. Often, one or both of an affected person’s parents have one copy of a mutated MUTYH gene.

MAP can result when a mutated gene copy is inherited from both parents, or one is inherited and a normal gene copy mutates (called an acquired or de novo mutation) early in development.

People with only one mutated copy of the MUTYH gene are called carriers and do not have symptoms. This means people with MAP may not have a family history of the condition, even if it was caused by inherited gene changes.

How common is MUTYH-associated polyposis (MAP)?

MAP is a rare disease and affects approximately 1 in 20,000 to 40,000 people.

How is MUTYH-associated polyposis (MAP) diagnosed?

MAP is diagnosed with exams, such as a colonoscopy, and genetic testing (usually a blood test).

Different types of polyps on a colonoscopy or endoscopy may raise concern for MAP. MAP may be suspected when:

• A person age 60 or younger has 10 or more colorectal adenomas
• A person of any age with 20 or more colorectal adenomas, hyperplastic polyps and/or sessile serrated polyps
• A person has at least 5 serrated polyps in the early portion of the colon with two or more larger than a centimeter, or more than 20 serrated polyps anywhere in the colon (sessile serrated polyposis syndrome)
• A person has a duodenal polyp or cancer
• Specific gene changes are found in a colorectal cancer sample, such as KRAS
• A person has a family history of polyps or colorectal cancer similar to people diagnosed with MUTYH-associated polyposis

Genetic testing must be done to diagnose MUTYH-associated polyposis. Both copies of the MUTYH gene must be mutated to cause MAP.

Gene testing may be a single gene test or a multigene panel that includes MUTYH as well as other genes, such as APC, that have been found in people with many polyps or a family history of polyps or cancer.

If someone in your family has MAP, you might want to ask your doctor about testing.

Does MUTYH-associated polyposis (MAP) increase a person’s cancer risk?

Yes, MAP increases a person’s risk of several types of cancer. Colorectal cancer is the most common cancer, affecting more than half of people with MAP by age 60.  However, it causes less than 1% of all colon cancers.  Without surveillance testing to remove polyps and monitor colon health, it is estimated that more than 80% of people with MAP would have colorectal cancer over their lifetime.

MAP is also associated with a few other types of cancer:

• Duodenal (small intestine) cancer
• Ovarian cancer 
• Bladder cancer

Other cancers, such as breast, endometrial, stomach, pancreas, thyroid and skin cancers, have been seen in people with MAP but it is not known if people with MAP are at an increased risk for developing these cancers.

How is MUTYH-associated polyposis (MAP) managed and treated?

There is no cure for MAP.  However, regular cancer surveillance tests can monitor and remove polyps before they become cancer or catch it earlier, when treatment could be more successful.

Management of MAP

Colorectal cancer surveillance

People with MAP often begin colorectal cancer surveillance between ages 25 to 30 with a colonoscopy.

A colonoscopy is a test where a doctor uses a small, flexible tube with a camera on the end to look at the inside of the colon. The tube is placed in the colon through the anus. You will often be given medication to help you relax for the procedure.

During the test, doctors will look at the number, size, and location of polyps. They may biopsy or remove polyps to check for cancer during the procedure. For many people with MAP, regular colonoscopies with removal of polyps keep colorectal cancer from developing. This test will be repeated every 1 to 2 years.

Upper GI tract cancer surveillance

People with MAP often begin tests to look for polyps or cancer in the small intestine between ages 30 to 35 with an upper endoscopy with side-viewing duodenoscopy.

For an upper endoscopy, a doctor uses a small, flexible tube with a camera on the end to look inside the stomach and small intestine. The tube is put into the stomach through the mouth. You will often be given medication to help you relax for the procedure.

This test will be done regularly, every few months to years, based on the results of the first test.

Other testing

Because thyroid nodules and cancer have been found in some people with MAP, doctors may recommend a thyroid ultrasound. Similarly, people with MAP may consider seeing a dermatologist, a skin expert, once a year to detect skin cancers early when they may be easier to treat.

Talk with your doctor about the tests that are best for you.

Treatment of MAP

Polyps found by surveillance endoscopy or colonoscopy are often removed. If colorectal polyps cannot be removed because of their size or number, then surgery to remove the colon, called a colectomy, may be recommended.

If cancer is found, the cancer is treated similarly to treatment for a person without MAP. The goal of regular testing is to prevent cancer or detect it early, when treatment is more likely to be successful.

Questions to ask your doctor

If you or a family member has MAP, consider asking your doctor:

• What is my risk of colorectal cancer?
• Does my family history increase my risk of getting colorectal cancer? Should I consider genetic testing?
• What cancer screening tests should I have?
• How many colon polyps have I had? What type were they?
• What can I do to reduce my risk of cancer?