Question: What is (are) MYH-associated polyposis ?
Answer: MYH-associated polyposis is an inherited condition characterized by the development of multiple adenomatous colon polyps and an increased risk of colorectal cancer. This condition, a milder form of familial adenomatous polyposis (FAP), is sometimes called autosomal recessive familial adenomatous polyposis because it is inherited in an autosomal recessive manner. People with this condition have fewer polyps than those with the classic type of FAP; fewer than 100 polyps typically develop, rather than hundreds or thousands. They may also be at increased risk for upper gastrointestinal polyps. MYH-associated polyposis is caused by mutations in the MYH gene.
Source: GARD

Question: What causes MYH-associated polyposis ?
Answer: What causes MYH-associated polyposis? Mutations in the MYH gene cause MYH-associated polyposis. Mutations in this gene prevent cells from correcting mistakes that are made when DNA is copied (DNA replication) in preparation for cell division. As these mistakes build up in a person's DNA, the likelihood of cell overgrowth increases, leading to colon polyps and the possibility of colon cancer.
Source: GARD