Genetics and Parkinson’s Disease
Many people affected by Parkinson’s disease want to know whether it can be passed down from one generation to the next. Directly inheriting the disease is quite rare. About 10 to 15 percent of all cases of Parkinson’s are thought to be genetic forms of the disease. The other 85 to 90 percent of cases are classified as idiopathic, meaning the exact cause is unknown.
Some research shows that having a first-degree relative with Parkinson’s disease, such as a mother, father or sibling, increases your risk of Parkinson’s twofold. People with an affected first-degree relative have about a three percent lifetime risk, as compared to people in the general population who have a 1 to 1.5 percent lifetime risk. So even if Parkinson’s runs in your family, the chance of you going on to develop the disease is still very low.
To date, abnormalities in particular genes have been linked to an elevated risk of Parkinson’s disease. The three most common genes related to Parkinson’s are the following:
- PARK2 (parkin)
- LRRK2 (leucine-rich repeat kinase 2)
- Glucocerebrosidase (GBA)
Mutations in the GBA gene are most common in the general population. And mutations in the LLRK2 gene are most common in certain ethnic groups, accounting for about 30 to 40 percent of Parkinson’s cases in North African Arabs and about 15 percent of Parkinson’s cases in people of Ashkenazi Jewish descent.
Even if you carry a gene mutation, it doesn’t mean you will be diagnosed with the disease. It’s not simply a mutation in one gene that matters. Experts believe that Parkinson’s disease is caused by a complex interaction of genetic and non-genetic factors.
The percentage of people with Parkinson’s who have a known gene mutation is very low, so genetic testing is not offered to every person with Parkinson’s. Usually genetic testing is done for research purposes only. The hope is that discoveries from research studies may open the door to new drug targets for Parkinson’s, or lead to tests that will determine who is at risk of developing the disease.
If Parkinson’s runs in your family and you want to get genetically tested, you should consult with a genetic counselor first. It’s a good idea to discuss the reasons for doing the testing and the impact it may have on you and your family. There are commercial companies offering genetic testing for Parkinson’s disease, but testing should be carried out by a neurologist and a counselor who specialize in genetic forms of Parkinsonism.