Gene Mutation Linked to Cause of Parkinson's Disease

A change in just one gene may affect the risk of Parkinson’s disease (search). That could lead to genetic testing for Parkinson’s, say scientists.

The gene in question is the LRRK2 gene. It’s the topic of three studies in the Jan. 18 online edition of The Lancet (search).

A single mutation in the LRRK2 g (search)ene occurs in about 5 percent of inherited Parkinson’s cases and 2 percent of isolated cases, experts report in The Lancet. The mutation was seen in familial Parkinson's disease as well as in patients without a family history of the disease.

In Parkinson’s disease, the brain’s movement signals to the rest of the body are garbled. That can cause tremors and trouble with movement and balance, although symptoms vary greatly from person to person.

Parkinson’s usually strikes after age 50, although it’s sometimes seen in people as young as 30. It occurs in more than 1 percent of people age 55 or older and 3 percent of those older than 75. Of the age-related nerve degenerative conditions, only Alzheimer’s disease is more common.

Several abnormal genes have been linked to Parkinson’s development but haven’t been flagged as a cause of the disease. Most researchers believe that both genetics and the environment play a role in the development of the disease. However, the role of genetics is not clear.

In the studies, researchers found that screening for the mutation will probably become a key component of genetic testing for susceptibility for Parkinson in the future.

Genetic Link to Parkinson's

The studies are from Italy, England, the U.S., Portugal, and Brazil. Two studies tracked the LRRK2 gene in patients with familial Parkinson’s disease. For comparison, one of those projects also looked at the DNA of healthy people. The third study focused on people with Parkinson’s disease without a family history of the disease.

All three studies suggest that the LRRK2 gene mutation affects Parkinson’s disease risk.

“Our results suggest that a single LRRK2 mutation causes Parkinson’s disease in 5 percent of individuals with family disease,” say William Nichols, PhD, of Cincinnati Children’s Hospital, and colleagues.

Likewise, another study linked the mutation to Parkinson’s disease in four out of 61 families with the disease from Italy, Portugal, and Brazil. That’s a little less than 7 percent of the families studied. The third study spotted the mutation in nearly 2 percent of isolated Parkinson’s cases.

The discoveries could eventually lead to genetic testing. “Screening for this mutation should be a component of genetic testing for Parkinson’s disease,” say Nichols and colleagues.

Genetic screening may also be a touchy topic, since a cure for Parkinson’s disease hasn’t been found yet. More studies are needed to see how frequently the mutation occurs, say the researchers.

By Miranda Hitti, reviewed by Brunilda Nazario, MD

SOURCES: Nichols, W. The Lancet, Jan. 18, 2005; online edition. Di Fonzo, A. The Lancet, Jan. 18, 2005; online edition. Gilks, W. The Lancet, Jan. 18, 2005; online edition. WebMD Medical Reference from Healthwise: “Parkinson’s Disease: What Happens.” WebMD Medical Reference from Healthwise: “Parkinson’s Disease: Topic Overview.” News release, The Lancet.