Hereditary Colorectal Cancer Syndromes: Less Common Syndromes
Two main inherited syndromes can lead to colorectal cancer:
Lynch syndrome, also known as HNPCC or hereditary non-polyposis colorectal cancer
Familial adenomatous polyposis (FAP)
But other less common inherited syndromes are linked with colorectal cancer as well. These include the following.
People with this rare disorder have a greater risk for polyps that can become cancer, colon cancer, and brain tumors. Changes (mutations) in a few different genes are linked to this syndrome. These include the gene linked to FAP and the genes linked to Lynch syndrome.
PJS (Peutz-Jeghers syndrome)
People with this rare inherited disorder may have:
Dark blue or brown spots or freckles in or around the mouth including the lips. The spots may also be around the eyes, nostrils, and anus. Dark spots may also appear on the fingers. These may fade by adulthood.
Many polyps in the gastrointestinal (GI) tract. These may be benign at first, but can become cancer over time.
Increased risk for noncancerous (benign) tumors of the ovaries or testicles
Increased risk for cancers of the stomach, small intestine, breast, ovaries, colon, lung, cervix, and pancreas
The abnormal gene in PJS is usually inherited from a parent, with each child having a 1 in 2 chance of getting the abnormal gene. In about 1 in 4 cases, the abnormal gene is not inherited, but occurs as a new gene mutation.
Juvenile polyposis syndrome
This is a rare inherited disease that typically appears before age 20. People with this syndrome have many noncancerous polyps throughout the GI tract. But there is a chance that these polyps can become cancer. Other symptoms can include diarrhea, GI bleeding, and an abnormal loss of protein from the GI tract (protein-losing enteropathy). Often it may seem that a child is the first in his or her family to have this disease. But it’s possible to inherit it from one parent who has the abnormal gene, but no symptoms.
MAP or MUTYH-associated polyposis
Mutations in the MUTYH gene raise the risk for multiple colorectal polyps or colorectal cancer. People with MAP may have just a few polyps, or hundreds of polyps. Unlike most colorectal polyp and colorectal cancer disorders, a person with MAP has defects in both copies of their MUTYH gene. The symptoms of MAP are very similar to both FAP and another form of that disorder called AFAP, or attenuated FAP. Genetic testing for mutations in the MUTYH gene is available. Testing should be considered if you may have FAP or AFAP, but don’t have a mutation in the gene linked to those disorders. Experts don’t know if people with only one MUTYH mutation have a higher than average risk for colorectal polyps and cancer.