Meyahealth
HomeGeneticsConditionMUTYH-associated polyposis
Back to Condition
MUTYH-associated polyposis
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Condition

MUTYH-associated polyposis

MUTYH-associated polyposis (MAP) is an inherited disorder characterized by a significantly increased risk of colorectal cancer and the development of multiple noncancerous polyps in the colon.

Overview

Most individuals with MAP develop ten to hundreds of benign polyps in the colon by age 50. Polyps may also occur in the small intestine or the stomach. Without monitoring and prompt follow-up, affected individuals have an 80 to 90 percent lifetime risk of developing colorectal cancer. Notably, individuals with MAP can develop cancer even in the absence of polyps.

While colorectal cancer is the most common malignancy associated with this condition, cancer can also develop in other areas, including:

  • The small intestine
  • The breasts
  • The lining of the uterus
  • The bladder

Frequency

The prevalence of MAP is estimated to be between 1 in 20,000 and 1 in 60,000 individuals worldwide. It accounts for nearly 1 percent of all colorectal cancer cases.

Causes

MAP is caused by germline variants (mutations) in the MUTYH gene. This gene provides instructions for producing an enzyme essential for base excision repair, a process that corrects DNA errors made during replication.

When MUTYH variants result in a non-functional or poorly functioning enzyme, DNA mismatch errors accumulate. If these errors occur in genes controlling cell growth, it can lead to uncontrollable cell division, resulting in polyps and cancer. For example, many colorectal cancers in MAP patients involve an acquired variant in the KRAS gene, which occurs because the MUTYH gene is not functioning properly.

Inheritance

MAP is inherited in an autosomal recessive pattern, meaning both copies of the gene in each cell must have a variant to cause the disorder. Parents of an affected individual each carry one copy of the altered gene. Individuals with only one altered copy may have a slightly increased risk of colorectal cancer compared to the general population, though the risk for other cancers remains unclear.

Frequently Asked Questions

Guidelines recommend starting colonoscopy at age 20‑25, or 10 years earlier than the youngest age of colorectal cancer in the family, whichever comes first. Surveillance is typically repeated every 1‑2 years because polyps can develop rapidly.
MAP is autosomal recessive, so each child has a 50 % chance of inheriting one mutated allele (becoming a carrier) and a 0 % chance of being affected if the other parent is not a carrier. If your partner is also a carrier, there is a 25 % chance the child will have MAP. Carrier testing for the partner can clarify risk.
high‑fiber, low‑red‑meat diet, regular physical activity, and maintaining a healthy weight are associated with reduced colorectal cancer risk. Some clinicians consider low‑dose aspirin or other chemopreventive agents, but evidence in MAP is limited; discuss any chemoprevention with your gastroenterologist.
Yes—MAP patients can develop cancer without a large polyp burden because microscopic dysplasia may be present. Ongoing colonoscopic surveillance with careful inspection, chromoendoscopy, or virtual colonoscopy, combined with biopsies of any suspicious mucosa, is essential even when no polyps are seen.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

Meyahealth

Ⓒ 2026. All rights reserved by MEYA

About UsTerms & PolicyFAQ