What is MUTYH-associated polyposis?

MUTYH-associated polyposis (MAP) is a hereditary disease that greatly increases the risk that intestinal polyps and colon cancer will occur. Both manifestations generally do not occur until adulthood. In addition, there is also an increased risk of developing polyps and malignant tumors of the duodenum. Manifestations outside of the gastrointestinal tract are possible as well.

How is MUTYH-associated polyposis diagnosed?

Suspected Diagnosis

MUTYH-associated polyposis is suspected with the following clinical findings:

  • Colon adenomas and/or colon polyps numbering:

    • 1-10 (at < 40 years of age)
    • 10 (at 40-60 years of age)
    • > 20 (at > 60 years of age)
  • 20 to hundreds of colon adenomas and/or colon polyps

  • Polyposis coli (z.B. >100 Dickdarmpolypen) ohne APC-Keimbahnmutation

  • Colon cancer at < 40 years of age

  • Frequent incidence of colon cancer in the family (± polyps)

Genetic Diagnostics

The diagnosis of “MUTYH-associated polyposis” is confirmed by detection of a mutation – or genetic change – in the MUTYH gene. Both copies of the gene need to be affected.

What is the risk of cancer?

With MAP, polyps generally do not occur until adulthood and are limited to between ten and a few hundred in number. These polyps have a tendency to progress, which can allow colon cancer to develop. However, it is also possible to suffer from colon cancer without polyps having developed beforehand. Without surveillance measures for early detection, the lifetime risk of developing colon cancer lies between 43% and 100%.

Nearly one fourth of MAP patients also have polyps in the duodenum. It is possible for malignant tumors to develop here as well, the lifetime risk of duodenal carcinoma is around 4%.

Furthermore, the following – at times malignant – manifestations can occur outside of the gastrointestinal tract:

  • Ovarian, bladder, breast, and uterine cancer.

  • Skin: benign and malignant tumors of the sebaceous glands, melanoma, squamous epithelial carcinoma, basal cell carcinoma, benign skin tumors

  • Thyroid: thyroid cancer, nodular goiter, singular thyroid nodules

  • Cysts in the jaw

What causes MUTYH-associated polyposis?

MUTYH-associated adenomatous polyposis is caused by a mutation – or genetic change – in the MUTYH gene. This gene encodes for the MUTYH protein, which repairs damage to the DNA that carries our genetic information. Now if the MUTYH gene is altered, the protein will no longer be able to function properly, meaning that it will not be possible for damage in the DNA to be repaired. This leads to the development of polyps and tumors.

Since MUTYH-associated polyposis involves a genetic disease, the gene mutation is passed on from one generation to the next. If two mutated genes come together in one individual, this person is homozygous with respect to this change, and the disease will appear. This kind of heredity is called autosomal-recessive heredity.

Is there a treatment?

Conspicuous colon polyps should always be removed. If it is not possible to remove individual polyps (polypectomy) due to the large number or high density of polyps, it should be considered whether the affected section of the colon should be removed. The complete surgical removal of the colon (colectomy) is recommended as soon as adenomas (benign tumors that are regarded as a preliminary stage of cancer) occur; however, this measure may be delayed depending on the size, histology, and number of adenomatous polyps. If colon cancer is diagnosed, a colectomy is inevitable.

Surveillance Recommendations for the Early Detection of Cancer

Surveillance Recommendations

No surveillance measures are recommended for children and adolescents.

The following recommendations apply for adults:

  • A colonoscopy every 2 years starting at the age of 18

  • A gastroscopy from 25-30 years of age

If someone with a MUTYH mutation wants to have children, conducting a genetic examination on his or her partner is worth considering before conceiving. This is advisable, since MUTYH-associated polyposis can only manifest if both parents pass on a mutated gene to the child (autosomal-recessive heredity).

Self-Care and Support

What should I pay special attention to?

People with this tendency to develop colon cancer should be cared for at a center that provides surveillance screening.

Regardless of any surveillance examinations, you should see a doctor as soon as you develop symptoms in the gastrointestinal tract. They may involve blood or mucous in the stool, stool abnormalities such as diarrhea or constipation, flatulence, or pain. Even non-specific signs such as weight loss should be paid attention to and reported to a doctor so that he or she can check whether you have colon cancer.

You should also see a doctor right away if you notice any other newly occurring abnormalities or symptoms, such as difficulty swallowing, skin lesions, or (lower) abdominal pain.

Support Groups and Additional Information