Two main inherited syndromes can lead to colorectal cancer:
Lynch syndrome, also called HNPCC (hereditary nonpolyposis colorectal cancer)
Familial adenomatous polyposis (FAP)
But other, far less common inherited syndromes are linked with colorectal cancer, too. These include:
People with this rare disorder have a lot of polyps, which increases their risk for colon cancer. They also have a higher risk for brain tumors. Changes (mutations) in a few different genes are linked to this syndrome. These include the genes linked to both FAP and 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. There might be dark spots on the hands and feet, too. They may fade by adulthood.
Many polyps in the gastrointestinal (GI) tract, often the small intestine. Polyps might also be found in the stomach, large intestine, as well as other parts of the body, such as the lungs, nose, and bladder. These may be not cancer (benign) at first, but can become cancer over time.
Increased risk for noncancer tumors of the ovaries or testicles
Increased risk for cancers of the stomach, small intestine, colon, breast, ovaries, uterus, lung, cervix, and pancreas
The abnormal gene in PJS is often inherited from a parent, with each child having a 1 in 2 chance of getting the abnormal gene. In some cases, the abnormal gene is not inherited, but is a new gene mutation.
Juvenile polyposis syndrome (JPS)
This is a rare inherited disease that mostly appears before age 20. People with this syndrome have many noncancer polyps throughout the GI tract. But there’s a chance that these polyps can become cancer.
JPS 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 their family to have this disease. But it’s possible to inherit it from a parent who has the abnormal gene, but no symptoms.
MAP or MUTYH-associated polyposis
Mutations in the MUTYH gene raise the risk for colorectal polyps and 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.
MAP symptoms are a lot like those of both FAP and another form of that disorder called AFAP (attenuated FAP). Genetic testing for mutations in the MUTYH gene can be done. It 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.