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PDF Interprets: A Genetic Link Between PD and Gaucher Disease

People who carry genetic mutations that cause the rare disorder known as Gaucher disease have at least five times the normal risk of developing Parkinson’s disease (PD), according to a report in the October 22, 2009 issue of the New England Journal of Medicine.

Clinicians had long noticed an association between Gaucher disease and PD.  In rare cases, people with Gaucher disease developed PD; more commonly, relatives of people with Gaucher disease had an increased incidence of PD.  These and other observed links between the two diseases prompted lead investigator Ellen Sidransky, M.D., of the National Human Genome Research Institute to study how frequently people with PD carry the genetic mutations known to cause Gaucher disease.

Sidransky organized a consortium of 64 researchers at 16 institutions around the world who were already analyzing the genetics of people with PD.  Gaucher disease develops when there is a change, or mutation, in a gene called GBA, which provides instructions for producing the enzyme glucocerebrosidase.  Normally a person has two working copies of the gene.  When both copies are mutated, Gaucher disease develops. (There are three types of Gaucher disease, each with a wide range of symptoms.)  A mutation in one copy of the gene causes no symptoms and was long thought to be harmless.  However, the new study found that being a carrier--having one mutated copy of GBA gene--increases a person’s risk of developing PD.  Scientists have identified nearly 300 different mutations that can occur in the GBA gene.  About one in 100 Americans carries one of these mutations.  Among Ashkenazi Jews, however, the mutations are more common: one in 15 people is a carrier.

The researchers focused on two common variants of the GBA gene.  In an ethnically diverse group of 5,691 people with PD they found that 3.2 percent had at least one of these variants, compared to 0.6 percent in a similar group of healthy people.  In a subgroup of Ashkenazi Jews, the incidence of one or more of these variants was 15.3 percent in people with PD and 3.4 percent in healthy people.

The newly identified genetic risk factor is the most common one found for PD to date, the researchers report.  Scientists have identified about a dozen genetic mutations known to play a role in PD.  Mutations in the GBA gene most likely increase susceptibility to PD, combining with other factors to result in disease.  The mechanisms by which this happens are not understood.  The researchers also found that people with PD who had mutations in GBA tended to have been diagnosed at a younger age and have a family history of PD, a lower incidence of bradykinesia (slow movement) and resting tremor, and a higher incidence of cognitive changes.


Source Date: Oct 21 2009