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More recently, clinicians have become aware that occasionally some patients, as they age, develop tremors and other Parkinson’s-like symptoms. Intravenous enzyme replacement therapy — which has helped children with Gaucher grow up with minimal symptoms since its introduction in the 1990s — does not impact neurologic symptoms, since the drug does not cross into the brain.
The gene for Gaucher disease is recessive, which means people must have two copies of the defective gene to experience symptoms. Those who inherit just one defective copy are carriers. About one in 100 people in the United States are carriers of the defective Gaucher gene, but the incidence is much higher among Ashkenazi Jews, where about one in 15 are carriers.
It was long assumed that people who were carriers didn’t have to worry about the disease, though some couples choose to get tested for the mutation because they don’t want to risk passing it along to their future children.
Dr. Pramod Mistry, a Gaucher expert and chief of pediatric gastroenterology and hepatology at Yale University School of Medicine, said scientists in both the Parkinson’s field and the Gaucher community were skeptical when reports surfaced in the late 1990s that there might be a connection between the two diseases. Mistry himself had become interested in such a possibility because folk singer Richard Meyer was his patient.
“One day he pulled me aside and said his guitar playing was becoming more clumsy because of tremor and unsteadiness,” Mistry recalled. “When I examined him, he had signs of Parkinson’s disease.”
A major study published in 2009 in the New England Journal of Medicine helped to persuade the naysayers. The international study, led by Sidransky at the NIH, reported that people who have Parkinson’s disease are over five times more likely to carry the mutated gene for Gaucher (GBA). Her team came to that conclusion after comparing the genetic profile of nearly 5,700 people with Parkinson’s (including 780 Ashkenazi Jews) with nearly 4,900 controls (387 of them Ashkenazi Jews).
Unlike Gaucher, which is a single-gene disease, multiple genes have been identified with Parkinson’s, though the mutations in the GBA gene are more common than the other genes. Still, “the vast majority of people with Gaucher disease never develop Parkinson’s,” Sidranksy said. Likewise, being a Gaucher carrier does not mean that Parkinson’s is in a person’s future. “It is not a predictive gene. It’s a risk factor,” he said.