Genetic tests offer knowledge, not wisdom

First success

The proliferation of screening tests was largely driven by the success of carrier screening for Tay-Sachs disease, another condition with high incidence among Ashkenazi Jews, or those of Eastern European descent.

Children with Tay-Sachs are unable to process a fatty substances, which builds up in the body and leads to blindness, deafness, paralysis and death by age 4. Since screening for Tay-Sachs carriers began in the early 1970s, the number of cases has dropped by 90%.

Other diseases that Ashkenazi Jews are frequently screened for include Canavan disease and Niemann-Pick disease, which lead to death in early childhood, and debilitating conditions like cystic fibrosis.

Dr. Ephrat Levy-Lahad, director of the Medical Genetics Unit at Shaare Zedek Medical Center in Jerusalem, and colleagues wondered how screening for a relatively mild condition like Gaucher affected couples' family planning decisions.

Gaucher disease is the most common genetic disease among Ashkenazi Jews. Scientists estimate that 6% to 10% of Ashkenazi Jews are carriers of at least one mutation that can lead to the disorder. Roughly 60% of eligible couples in Israel take the screening test, Levy-Lahad said.

But among the eight to 14 Jewish genetic diseases commonly screened for, it is also the most controversial, Grinzaid said. Even knowing which mutations are in a fetus' genes, she said, "we're still not able to predict what's going to be wrong with the child. It can be anywhere from something that presents in childhood, which is treatable, to something that can never present. . . What do you do with that?"

Among children who inherit two faulty genes, the most common result is Type 1 Gaucher. Half will become symptomatic at some point in their lives, when harmful amounts of glucocerebroside build up in the spleen, liver, lungs and bone marrow.

Patients can experience pain and suffer from fatigue, although the symptoms can be treated with biweekly infusions of the enzyme that their bodies fail to produce in sufficient quantities. The intravenous infusions take an hour or two at home and cost $100,000 to $400,000 a year.

The researchers surveyed all 10 centers in Israel that screen for Gaucher disease mutations. Between 1995 and 2003, the centers tested about 28,900 people and identified 83 couples where both partners had a mutation.