HNPCC - A Hereditary Cancer Syndrome

HNPCC stands for Hereditary Non Polyposis Colon Cancer - HNPCC is a hereditary syndrome that is caused when a person inherits a mutation in one of five different genes. HNPCC is also called Lynch Syndrome, after Dr. Henry Lynch who realized that it was a separate disorder from other hereditary colon cancers. HNPCC is not a form of cancer, rather a syndrome that puts people at high risk for colon cancer. If people born with HNPCC do not undergo regular screening beginning at an early age, they have an 80% chance of developing colon cancer. This type of cancer (HNPCC) accounts for 5-6% of all colon cancers.

How is HNPCC Inherited?

Parents with HNPCC have a 50% chance of passing the HNPCC gene to each of their children. Individuals who do not inherit the gene cannot pass it to their own children. Unfortunately, some individuals with HNPCC do not have an affected parent. These individuals, who are the first to have the condition, are referred to as having a new altered gene mutation. Once they acquire the mutated gene, they can pass this HNPCC gene to their children.

What Causes HNPCC?

The cause of HNPCC is caused by damaged genes. Specifically, there have been genetic markers identified which is reflective of micro satellite instability. The DNA mismatch repair genes have been identified as HMSH2, HMLH1, HPMS1, and HPMS2. If you have been identified as having HNPCC, then one or more of these genes will show micro satellite instability. Patients with HNPCC usually develop colon cancer at an earlier age than the general population. There is a propensity for right-sided lesions.

How is HNPCC Diagnosed?

HNPCC is diagnosed usually after one or more family members develop colon cancer. The family history is examined to see if there is cause and effect. This is usually accomplished by genetic counseling. The primary method that doctors and genetic counselors determine if you have HNPCC is by looking at the types of cancer and age at which cancer developed in you or your family.

If the genetic counselor you or your family does have HNPCC, the next step usually involves looking at tumors from people in your family (if they are available). If the tumors suggest that there is a detectable genetic error predisposing your family to HNPCC, the next step is a genetic test to try to identify the error. If someone in your family is found to have an error in one of the genes associated with HNPCC, then other family members can be tested for the same error to find out if they too have inherited the predisposition to HNPCC.

What Can I Do?

If you suspect you might have HNPCC, the best things you can do are research your family history and then meet with a genetic counselor. An ideal method is to create a flowchart of your family history going back 3 or more generations. List the relatives and determine if any of them had colon cancer, and if they had died from the disease. Then schedule an appointment with a genetic counselor to review the information. She will ask additional questions and determine if a genetic test is recommended. If someone in your family has recently been diagnosed with the cancer, then they are an ideal candidate to have the test performed. They will need to provide a tumor sample.

Colon Cancer Prevention through Screening

If your family has a history of colon cancer or you have the HNPCC gene, then you must get screenings done earlier than the general population, and more frequently. The standard method is colonoscopy. With colonoscopy, the doctor will examine the colon and small bowel with a flexible fiber optic camera. The doctor will search for small growths called polyps. If any are encountered, they will be removed during the procedure and sent for biopsy. Polyps are benign when they first develop but will eventually evolve in cancer if left undisturbed.

Final Thoughts

Depending on your family history, you could have a colonoscopy beginning at age 20. The general population is recommended to have a colonoscopy at age 50 and every 5 years thereafter if no problems or family history of cancel is evident. The frequency and age to start will need to be decided with consultation with your family and your doctor. If you have any symptoms such as dark purple colored stool, blood in the stool or rectal bleeding, consult your doctor immediately. It could mean the difference between life and death.

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