American Board of Internal Medicine (ABIM) Certification Practice Exam

MYH-associated polyposis is what type of genetic disorder?

1. Autosomal dominant

2. Autosomal recessive

3. X-linked

4. Multifactorial

The correct answer is: Autosomal recessive

MYH-associated polyposis is classified as an autosomal recessive genetic disorder. This means that an individual must inherit two mutated copies of the MYH gene, one from each parent, to develop the condition. In autosomal recessive disorders, carriers—those with only one mutated copy—do not typically exhibit symptoms of the disease, as the presence of one normal copy of the gene is usually sufficient for normal function. MYH-associated polyposis is characterized by the development of multiple adenomatous polyps in the colon and an increased risk of colorectal cancer. The specific mutations in the MYH gene lead to a failure in the base excision repair pathway, resulting in an accumulation of mutations in the colorectal epithelium. In this context, other genetic disorder types can be differentiated based on inheritance patterns: - Autosomal dominant disorders require only one copy of the mutated gene to manifest the disease phenotype, which is not the case for MYH-associated polyposis. - X-linked disorders are linked to genes on the X chromosome and typically affect males more severely due to their single X chromosome, which doesn't apply to this condition. - Multifactorial traits involve a combination of genetic and environmental factors, rather than being attributed to a single gene