Doctors Unveil Two Gaucher Studies
A broad screening program in Israel for Type 1 Gaucher disease, the most common of the Jewish genetic diseases, is proving controversial, Israeli researchers noted in a September 2007 study in the Journal of the American Medical Association.
Screening programs are encouraged for severe diseases where couples at risk could be identified before giving birth to an affected child — such is the case in the fatal Jewish genetic disease Tay-Sachs — but they are controversial for Gaucher disease because the most common Type 1 mutation is “usually not severe or untreatable, and the test performed does not fully predict disease severity,” the study said.
Of the 83 couples found to be Gaucher carriers, pregnancies were terminated for two of 13 affected fetuses found to have asymptomatic or mild forms of the disease, and for two of three moderately affected fetuses.
“You can’t give the parents the information they need to make an informed decision, and that’s particularly true with the N370S mutation, which is most common in the Jewish population,” said Ernest Beutler of the Scripps Research Institute in La Jolla, Calif. “It creates more problems than it solves.” To accompany the study, Beutler wrote an editorial that argued against screening.
Screening for Gaucher disease is offered worldwide and has been offered in Israel since 1995. But the screening program tests for a number of mild mutations that are the most prevalent, and not for the more severe mutations, which are too rare to warrant screening, said Ari Zimran, director of the Gaucher Clinic at Shaare Zedek Medical Center in Jerusalem.
The study, conducted by master’s degree candidate Shachar Zuckerman under the supervision of Ephrat Levy-Lahad of the Medical Genetics Unit at Shaare Zedek, did find a significant correlation between genetic counseling and pregnancy continuation. Among the couples with affected fetuses, only one of 13 who consulted with a Gaucher expert terminated their pregnancy, compared with three of three who had not. Of those couples predicted to have a child affected by the mild mutation, no pregnancies were terminated when parents consulted with a genetic counselor, and two were terminated with no consultation.
Though Zimran believes that screening causes “a lot of anxiety and unnecessary stress,” he does not believe this study will prompt any change. According to him, there are too many outside factors, including monetary interests from drug companies and genetic centers, keeping Gaucher in the Ashkenazic screening package.
The study suggested that “the main possible benefit of screening was allowing couples at risk to be identified and make an informed choice.”
Ashkenazic Jewish carriers of Gaucher disease, one of the most common of the Jewish genetic diseases, have an increased risk of getting Parkinson’s disease, a new study found.
The study, conducted by researchers at the Tel Aviv Sourasky Medical Center, found that among Ashkenazic Jews, 18% of 420 Parkinson’s patients had mutations for Gaucher disease. In contrast, mutations were seen in only 4.2% of elderly Ashkenazic controls without Parkinson’s disease, and 6.35% of 3,805 young controls.
The study also found that severe mutations of Gaucher disease in the Ashkenazic Jewish population increased the risk of Parkinson’s by 13-fold, compared with a lower risk for those with mild mutations.
“There seems to be something about having a mutation in this gene which increases your risk for developing Parkinsonism, but it’s not predictive,” warned Dr. Ellen Sidransky, senior investigator at the National Human Genome Research Institute of the National Institutes of Health, located in Bethesda, Md. “Most patients with Gaucher disease never develop Parkinson’s.”
Despite the clear correlation, the study does caution that there could be outside factors involved in the risk of developing Parkinson’s. Since the vast majority of Gaucher carriers never develop Parkinson’s, it is likely that the disease risk is influenced by additional genetic modifiers and environmental factors. Those issues, as well as other medical factors that modify the onset of Parkinson’s, must be taken into consideration before meaningful genetic counseling can be offered.
Though this is not the first study to find this correlation, it is the largest study conducted with Jewish subjects. Since Gaucher disease is most common in the Ashkenazic Jewish population (According to the National Gaucher Foundation, one in 15 Ashkenazic Jews is a carrier of Gaucher disease), Ashkenazic patients with Parkinson’s have a higher frequency of Gaucher mutations, but in non-Jewish populations there is still a correlation between Gaucher mutations and Parkinson’s.
In March 2007, researchers found a link in Chinese subjects from Taiwan, and other researchers have seen Gaucher mutations in Parkinson’s patients all over the world. Sidransky said that an ongoing international study about the linkage between the two has thus far shown that Parkinson’s patients are five to six times more likely to have a Gaucher mutation.
Though more research needs to be done, understanding the relationship between Gaucher mutations and Parkinson’s could provide insight into the genetics, pathogenesis and treatment of the disease, Sidransky said. In the future, “we may be able to devise therapies specific for these Parkinson’s patients,” but “it’s early. It’s certainly going to stimulate a lot of research.”