Is Parkinson's Disease Inherited?

Genetics' role not entirely known in affected families

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Genetics very likely plays a role in all types of Parkinson's disease. However, while having a specific combination of genetics may increase your risk of the disease, it doesn't necessarily mean that you'll get it.

Around 15 to 25 percent of people living with Parkinson's have a family history of the condition, either an immediate or second-degree relation. Having one or more of these relatives will place you at slightly higher risk for Parkinson's, but it's still no guarantee you'll develop the disorder.

Conversely, if you have Parkinson's, it shouldn't suggest that any of your kids or grandkids will get the disease either. It merely indicates that their risk is slightly above those without a family history.

In the end, most cases of Parkinson's don't have any known cause (which we refer to as either having idiopathic or sporadic disease). While there are forms that seem to run in families, these account for a small percentage of cases — roughly five to 10 percent, all told.

Key Gene Mutations Associated With Parkinson's

There are forms of Parkinson's that appear to be influenced by genetic defects that run in families. We tend to see this with early-onset forms of the disease wherein symptoms being to appear far earlier than average onset age of 60.

One type of genetic mutation associated with familial parkinsonism is in the so-called SNCA gene. This is the gene linked with the production of alpha-synuclein protein, a biomolecule which can contribute to abnormalities in nerve cells.

While rare in the general population, the SNCA gene mutation has been identified in around two percent of families affected by Parkinson's.

In 2004, scientists discovered a similar genetic mutation in a number of families in whom multiple members had been affected. The so-called LRRK2 mutation is today linked to about one to two percent of all Parkinson cases, mostly affecting people of Jewish, Ashkenazi, North African Arab-Berber, or Basque origin.

Another mutation involving the GBA gene is already known to cause Gaucher's disease (a hereditary disorder characterized by bruising, fatigue, anemia, and the enlargement of the liver and spleen). Research has since shown that the GBA mutation is present in a significant number of people with Parkinson's, suggesting a causal link between the mutation and the disease.

Genetics and Environmental Factors

Environmental factors are also significant contributors to the development of Parkinson's and may, in some cases, work in tandem with genetics to cause the disorder. A study in 2004 showed that people who had a mutation of the CYP2D6 gene and were exposed to pesticides were twice as likely to develop Parkinson's.

On their own, pesticides, metals, solvents, and other toxicants have each been loosely linked to Parkinson's. But what's interesting is that those who had the CYB2D6 mutation and were not exposed to pesticides were not found to be at any higher risk of developing the disorder.

A Word From Verywell

Although there may be no direct benefit to you at the present time, the results of genetic testing can help further Parkinson’s research by allowing scientists to better understand the disease and develop new treatments.

While the choice to test is a personal one, it may be of benefit if multiple family members have been affected or if you are at high risk based on your ethnicity.

Sources:

Lesage, S. and Brice, A. "Parkinson's disease: from monogenic forms to genetic susceptibility factors.". Human Molecular Genetics. 2009; 18(R1):R48-59.

Stewart, A.; Factor, D.; William J. et al. Parkinson’s Disease: Diagnosis and Clinical Management (2nd edition). New York: Demos Medical Publishing; 2008; ISBN-10: 1933864001.

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