Comprehensive COLARIS AP®
POSITIVE FOR TWO COPIES OF AN MYH MUTATION
 This test result means that the test detected deleterious mutations in both of the MYH genes, indicating a diagnosis of MYH-associated polyposis (MAP). This syndrome is associated with an increased risk of colorectal adenomas and cancer. Cancer risks for MAP are currently unknown, although the association with multiple adenomas is thought to increase the risk of colon cancer significantly.
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COLARIS AP® Positive for Two Copies of an MYH Mutation
This result allows you to personalize your patient's medical management, as the diagnosis of MAP is genetically confirmed. It also enables other family members to determine whether they also inherited both of the mutations and the associated cancer susceptibility.
Medical Management Recommendations
It has been recommended that the medical management of individuals who have biallelic MYH mutations be similar to individuals known to carry a germline APC mutation, depending on the patient's adenoma burden. This medical management should include regular colonoscopies and upper GI screening for duodenal polyps.
The following are medical management recommendations for patients with germline APC mutations and can be adapted for patients with biallelic MYH mutations:
COLORECTAL CANCER
Increased Surveillance
 Familial Adenomatous Polyposis (FAP)
- Flexible sigmoidoscopy annually, beginning at age 10-12
- Esophagogastroduodenoscopy (EGD) every 1-3 years (depending on adenoma burden) beginning at age 20-25
Attenuated FAP (AFAP)
- Colonoscopy every 1-3 years, beginning during the late teens to early twenties
- Esophagogastroduodenoscopy (EGD) every 1-3 years (depending on adenoma burden) beginning at age 20-25
Prophylactic Surgery
FAP
- Colectomy following the development of adenomas
AFAP
- For patients diagnosed with AFAP, prophylactic colectomy may not be necessary; surgery should be considered on an individual case-by-case basis
Post Colectomy
- Flexible sigmoidoscopy (following prophylactic subtotal colectomy) of the remaining ileal pouch and rectal epithelium every 6 months to 3 years, depending on the number of adenomas found during the previous exam
* Optional post-surgical chemopreventive agents if surgery is rectum sparing
EXTRA-COLONIC CANCER
Surveillance
- Screening for other FAP/AFAP cancers (thyroid, brain, pancreatic, hepatoblastoma, etc.) may be considered
Implications for Family Members
Once biallelic MYH mutations have been detected in a family, other family members can be tested for the specific family mutations. Most importantly, since mutations in this gene are inherited in an autosomal recessive pattern, siblings are at 25% risk to carry the same two MYH mutations. Siblings testing positive for the known mutations are managed more aggressively in order to allow for early cancer/adenoma detection and sometimes even cancer prevention. By contrast, siblings who did not inherit the family mutations are not at increased risk for cancer/adenomas and may adhere to general population screening guidelines.
Aside from siblings, other family members may also be at risk to have one or both of the gene mutations found in your patient. For example, his or her children will definitely be carriers of one MYH mutation. If the patient's partner is of European descent, there is a 2% chance that he/she will also carry a single MYH mutation. If this partner is truly a carrier, the patient's children will have a 50% risk to carry biallelic MYH mutations, one from their parent who is affected with MAP and one from the parent who is a carrier of a single MYH mutation. There are currently no recommendations with regards to carrier genetic testing in partners of patients with biallelic MYH mutations.
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