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Lynch Syndrome
Introduction
Lynch syndrome is a rare disorder also known as hereditary nonpolyposis colorectal cancer (HNPCC) syndrome. Though not a cancer in its own right, Lynch syndrome strongly predisposes people who have this inherited defect to develop colorectal cancer as well as several other types of cancer. The condition is named after Henry Lynch, a doctor and authority on inherited cancers.
Lynch syndrome is caused by mutations or alterations of particular genes. People with Lynch syndrome have more than an 80 percent chance of developing colorectal cancer during their lifetime. Colorectal cancer is relatively common, but only about 3 percent to 4 percent of all colon cancer cases are attributable to Lynch syndrome.
When colorectal cancer is associated with lynch syndrome, it tends to occur at a younger age than in most other colorectal cancer cases. If your family history suggests that Lynch syndrome may be present, genetic testing can determine if you have Lynch syndrome so that you can consider steps to either prevent the development of colon cancer or at least detect it at an earlier, more treatable, stage.
Signs and symptoms
Although the term "nonpolyposis" appears in the name "hereditary nonpolyposis colorectal cancer," people with Lynch syndrome actually do have polyps, mushroom-like growths of tissue, in the lining of the colon or rectum. However, these polyps tend to be fewer in number compared with the number present in other forms of inherited colorectal cancers such as familial adenomatous polyposis (FAP).
When cancer does occur in people with Lynch syndrome, most cases arise in the right side of the colon. Colorectal cancer associated with Lynch syndrome tends to occur in people at a younger age than for people with the more common nonhereditary forms of colorectal cancer.
In addition to the presence of early polyps, the colorectal cancers associated with Lynch syndrome share many of the same signs and symptoms as other types of colorectal cancer. Although these cancers are often "silent" or symptom-free in their early stages, the following signs and symptoms may be present as the cancer becomes more advanced:
- Changes in bowel habits — for example, constipation or diarrhea that persists for longer than several days.
- Visible blood in the stool, which may indicate rectal bleeding.
- Black, tarry stool, which may represent bleeding above the rectum.
- Iron deficiency without another identifiable cause.
- Abdominal cramps or pain.
- Feelings of fatigue or weakness.
- A decline in appetite.
- Unexplained weight loss.
Lynch syndrome runs in families. You can inherit it from either parent in an autosomal dominant inheritance pattern. If you have this condition, there's a 50 percent risk of passing the mutated gene to your children.
The defective gene inherited in Lynch syndrome is responsible for correcting mistakes that may occur when DNA replicates in normal cells. DNA is the genetic material that contains instructions for every chemical process in the body. When our normal cells grow and divide, they must first make a new copy of their entire DNA. It's not uncommon for some minor mistakes to be made during this process, but normal cells have repair mechanisms to recognize when a mistake has been made, and to repair that mistake before a cell divides to form two new cells. However, people who inherit the abnormal gene associated with Lynch syndrome lack the ability to repair these minor mistakes. An accumulation of these mistakes leads to increasing genetic damage within cells and eventually can lead to the cells becoming cancerous.
Treatment
When polyps associated with Lynch syndrome are present, doctors remove them during a colonoscopy. If colorectal cancer is already present, treatment is the same as for other forms of colorectal cancer.
Surgery
When colorectal cancer is detected during a colonoscopy in people with Lynch syndrome, doctors typically advise an operation to make sure all of the cancer has been removed. You should also discuss with your doctor an operation to remove the entire colon (colectomy), but not necessarily the rectum as well.
Surgery may also be an option in people who carry the genetic mutation of Lynch syndrome, even if they don't yet have colorectal cancer. This prophylactic colectomy eliminates the risk of cancer of the colon. Most people with Lynch syndrome choose frequent colonoscopies over prophylactic surgery.
Although colectomies can be performed in a number of ways, a common approach is called total abdominal colectomy with ileorectal anastomosis. This involves the removal of the colon, and then attaching the remaining small bowel to the rectum. Because the rectum remains in place, the person can have normal bowel movements, and thus there is no need for a bag to collect human waste (a colostomy or ileostomy bag).
Other approaches
Additional treatment choices include:
- Chemotherapy, which uses drugs to destroy cancer cells. This approach often follows surgery.
- Radiation therapy, which uses high-energy external beam X-rays after surgery to kill remaining cancer cells.
Prevention
In addition to the regular use of colonoscopy, genetic testing is an important preventive tool. In major medical centers, genetic counselors who specialize in cancer-related mutations can help you determine your risk of Lynch syndrome, and can provide guidance on ways to prevent or detect colorectal cancer at its earliest stages.
These counselors or your doctor may recommend that you and other family members be tested for the presence of genetic mutations. Testing involves drawing a blood sample and sending it to the lab for analysis. When test results are available, a genetic counselor can explain what the findings mean.
Another good approach is to follow the general recommendations of the American Cancer Society for preventing colorectal cancer, which include:
- Stop smoking.
- Keep your body weight at normal levels.
- Limit the high fat foods in your diet.
- Consume plenty of vegetables, fruits and whole grain foods.
- Exercise regularly.
Information obtained from National Institute of Health