Peutz-Jeghers Syndrome

The risk for breast and ovarian cancer is increased with Peutz-Jeghers syndrome (PJS), a rare early-onset autosomal dominant disorder, associated with specific physical characteristics in addition to increased cancer risks. The features associated with PJS may include the following:

  • Melanocytic macules (dark blue or brown moles)These moles may be located around and/or in the mouth (including the lips), and around the eyes, nostrils, and anus. Dark moles may also appear on the fingers. These lesions may fade by adulthood.

  • Multiple polyps in the gastrointestinal tract

  • Increased risk of benign (noncancerous) tumors of the ovaries and testes

  • Increased risk of stomach, esophageal, breast, colon, pancreatic, cervical, and ovarian cancers

Peutz-Jeghers syndrome is caused by mutations in a gene on chromosome 19 known as STK11. Genetic testing is available clinically. Mutations in STK11 are identified in nearly all individuals with a positive family history and about 90 percent of individuals with no previous family history. Almost all people with PJS will be diagnosed with one or more of the associated cancers during their lifetime.

The STK11 gene is a tumor suppressor gene, which usually controls cell growth and cell death. Both copies of a tumor suppressor gene must be altered, or mutated, before a person will develop cancer. With PJS, the first mutation is inherited from either the mother or the father and is present from birth in all cells of the body. This is called a germline mutation. Whether a person who has a germline mutation will develop cancer and where the cancer(s) will develop depends on where (which cell type) the second mutation occurs. For example, if the second mutation is in the breast, then breast cancer may develop. If it is in the colon, then colon cancer may develop. The process of tumor development actually requires mutations in multiple growth control genes. Loss of both copies of STK11 is just the first step in the process. What causes these additional mutations is unknown. Possible causes include chemical, physical, or biological environmental exposures or chance errors in cell replication.

Some individuals who have inherited a germline STK11 mutation never develop cancer because they never get the second mutation necessary to knock out the function of the gene and to start the process of tumor formation. This can make the cancer appear to skip generations in a family, when, in reality, the mutation is present. People with a mutation, regardless of whether they develop cancer, have a 50/50 chance to pass the mutation on to each of their children.

It is also important to remember that the STK11 gene is not located on the sex chromosomes. Therefore, mutations can be inherited from the mother's side or the father's side of the family.

Do You Need to Be Tested?

You should consider genetic testing if:

  • You have had a certain kind of polyp called a Peutz-Jeghers polyp
  • You have a family history of Peutz-Jeghers polyps and have freckling in the tongue and lips
  • You have a family history of Peutz-Jeghers syndrome

Why You Want to Know

Knowing if you have a mutation in STK11 can provide you with resources to detect cancers early as well as reduce your risk of developing certain cancers.  Once a mutation is identified in a family, other family members who are at risk can see if they inherited the same mutation.

How You Can Learn More

Ask your doctor if you’re at risk for Peutz-Jeghers or call 1.800.4BAYLOR to learn more about the genetic counseling process.

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