Increased study of Jew-netics

DENA DAWSON

It's hard to open any publication lately without reading about discoveries in genetic research. Investigators are looking into why some people are more generous than others, and some are investigating whether Jews are smarter than the general population. Other studies have focused on Jews' origins and how Judaism's oral history measures up to the findings of genetic science. Then, there are the important links between genes and health.

Genes change over time. Genetic disorders occur when one or both copies of a specific gene undergo an alteration or a mutation. That mutation is then inherited in offspring.

Jewish genetic disorders are a group of conditions that are common among Ashkenazi Jews. These diseases also affect non-Jews, but Ashkenazi Jews are affected 20-100 times more often. Sephardi Jews are also affected by genetic disorders, but their list contains only four such diseases – quite small compared to the Ashkenazi list of 14-17.

One of the most common "Jewish diseases" is Tay-Sachs. The occurrence is quite frequent: one in 30 Ashkenazim is a carrier. Babies with Tay-Sachs seem to be fine for the first six months of life, but later undergo a serious decline. The child becomes blind and deaf and can't swallow. Paralysis is next, followed by death at around the age of four or five. The adult version of the disease, however, is not fatal.

In the 1970s, Jewish communities were successful in diagnosing Tay-Sachs. Before 1970, about 50-70 infants a year were affected. Now, the disease has essentially been eliminated, thanks to mass screening and genetic counselling.

Ashkenazim are also more susceptible to Crohn's disease: they are twice as likely as the general population to develop it. Crohn's is characterized by inflammation of the final section of the small bowels and parts of the colon. It is a long-term condition that typically begins in young adulthood, most often between ages 15 and 40. Symptoms of Crohn's include serious diarrhea, abdominal cramping, blood in the stool, intestinal ulcers, reduced appetite and attendant weight loss and abscesses.

Fortunately, medications are very effective in improving the symptoms of Crohn's. The recent introduction of an injectable drug has revolutionized treatment. Surgery is another possibility, generally involving the removal of a section of the bowel – up to 50 per cent of all Crohn's sufferers will have at least one operation during the course of their disease.

Gaucher's disease, caused by the deficiency of an enzyme, occurs in about one in 1,000 Ashkenazi Jews and one in 12 Jews are carriers. In order for the disease to be transmitted, both parents must be carriers of the identified mutation, in which case, there is a 25 per cent chance that their child will be affected.

The symptoms of Gaucher's disease involve a fatty substance that accumulates in the bone marrow, spleen, liver and other parts of the body, resulting in enlarged organs and skeletal disorders. The disease commonly features anemia, low platelet count, easy bruising and bleeding, bone pain and bone fractures from slight trauma. People affected most seriously may also be more susceptible to infection.

For many patients with Gaucher's disease, frequently injected enzyme replacement treatment can dramatically reduce liver and spleen size and skeletal abnormalities. Blood transfusion may benefit some anemic patients.

Diagnosis of Gaucher's disease is made with genetic testing. Numerous different mutations are involved, so testing sometimes require full sequencing of the gene to confirm diagnosis. Prenatal diagnosis is available and useful when there is a known genetic risk factor appearing in the family history.

Finally, between five to 10 per cent of all breast cancer cases are hereditary, meaning they are due to a genetic mutation that has passed through the family. The cancer itself is not inherited, but an increased predisposition can be passed down to individuals carrying certain genes.

It is estimated that one out of every 50 Ashkenazi Jews carries a mutated copy of genetic markers that predispose to cancer. Most startlingly, women who inherit the mutant form of one of these genes may have up to an 80 per cent risk of contracting breast cancer, compared to 12 per cent in the general population.

Right now, for the first time in Canada, Jewish women are being offered the chance to alter their genetic destiny by taking a free test that will determine if they are at high risk of developing breast cancer. By screening for three inherited breast cancer gene mutations common to those of Ashkenazi descent, the Woman's College Research Institute has an ambitious goal: to prevent the disease before it strikes. If expanding genetic testing to this group proves worthwhile, it could change testing across Canada by recognizing an inherent risk of cancer, simply due to ancestry.

Dena Dawson is a Vancouver freelance writer.

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