Individuals who have MYH-associated polyposis syndrome (MAP) usually have between 15 and 100 colon polyps develop throughout their lifetime. If untreated, there is an 80 percent lifetime risk for colon cancer and 5 percent increased risk for duodenal cancer.
Other characteristics of MAP include polyps of the upper gastrointestinal system, CHRPE (areas of increased pigmentation in the eye), osteomas (benign bone tumors), extra or impacted teeth, and non-cancerous tumors of the hair follicle.
Once someone is identified as having MAP, it is possible to take steps to reduce the risk of cancer. For people who have cancer already, they will need to be monitored for other cancers.
MAP is not inherited in the same way as other hereditary cancer syndromes. MAP is much more likely to skip generations, and occurs when people have two mutations in the MYH gene.
The brother or sister of anyone with MAP has a one in four chance of also having MAP. The parents and children of anyone who has MAP have a low risk of also having MAP, but they may be at increased risk to develop colon cancer.
Our cancer genetic counselors can discuss your personal risk in more detail. They also can offer genetic testing to help clarify who in the family has MAP, and who may be at increased risk for colon cancer.