One in six people who develop Parkinson's disease early (before age 40 or 50) carry a genetic mutation known to be associated with the neurological disorder, new research suggests.
And people of Jewish or Hispanic ancestry, as well as those who develop the disease very early, are more likely to carry one of these gene mutations, as are people who have a close relative with Parkinson's disease, the study found.
The findings don't mean that people should go out and get tested for the mutations if they don't have Parkinson's, Dr. Roy N. Alcalay of Columbia University in New York City told Reuters Health; however, he added, genetic counseling could be useful to people with the disease. Right now, the researcher pointed out, there's really no way to prevent Parkinson's in individuals at risk.
Alcalay and his colleagues at 13 centers across the United States tested 953 patients with early-onset Parkinson's disease for mutations in six genes known to be associated with the illness; 77 of them were of Hispanic ancestry, and 139 were of Jewish ancestry. In this study, early onset meant the patients developed the illness before age 51.
Overall, 158 participants (nearly 17 percent) had mutations in one of the six genes, the researchers found.
Among people who developed Parkinson's at age 30 or younger, nearly 41 percent carried a mutation, compared to about 15 percent of those who first developed symptoms between 31 and 50 years of age.
Nearly a third of the participants with Jewish ancestry carried a mutation, compared to 14 percent of those with no Jewish heritage. Sixteen percent of Hispanic patients had mutations in the Parkin gene, compared to 6 percent of non-Hispanics.
Among people with a parent, sibling or other first-degree relative with Parkinson's, 24 percent carried a mutation associated with early-onset disease, compared to 15 percent of people without a close relative with the disease.
Parkinson's is a complex condition, Alcalay noted, involving a number of environmental factors as well as several different genes. The new findings illustrate how much progress has been made in understanding the disease, he added, given that just 11 or 12 years ago there were no known genes associated with the illness. In that sense it's very exciting, he said.
Based on the findings, the researcher said, people with early-onset Parkinson's disease who are of Jewish or Hispanic ancestry, as well as individuals who developed the disease at 30 or earlier, might benefit from meeting with a genetic counselor to talk about their risk of carrying one of these mutations, and discuss whether or not they want to get tested for it. People with a first-degree relative with Parkinson's might also benefit from genetic counseling, he added.
The probability that someone who carries one of these genes will actually develop early-onset Parkinson's is unknown, Alcalay and his colleagues emphasize in their report.
For this reason, they say, there is little or no role at present for prenatal testing for these mutations, or for using genetic testing for the genes in family planning or to predict a person's risk of the illness.