Many people affected by Parkinson’s disease (PD) want to know whether it can be passed down from one generation to the next. Only about 10 to 15 percent of all cases of Parkinson’s are thought to be genetic forms of the disease (monogenetic). The other 85 to 90 percent of cases are classified as sporadic (or occasional).
Recent studies have begun to demonstrate an important influence of genetic factors on the clinical aspects of the more common sporadic disease.
Whether it is you or your loved one who is living with Parkinson’s, you may be wondering how the new genetic discoveries will affect you and what they mean for your own risk or that of your children. Having first degree relative with Parkinson’s disease increases your risk of having the disease. In the long run, scientists hope to define methods of distinguishing subtypes of Parkinson’s at the earliest stages and implement disease modifying strategies specific to the subtype.
Understanding the Genetics Behind Familial Parkinson’s
Familial Parkinson’s disease types include:
- Autosomal dominant: the presence of one altered copy of this gene is sufficient to cause the disease. This kind of genetic Parkinson’s is rare, (one to two percent of people with PD). Examples include: A protein in the human brain that is associated with the development of Parkinson’s. It is the main component of Lewy bodies. (SNCA) and Mutations in this gene are the most common cause of inherited Parkinson’s. Researchers have identified more than 100 LRRK2 gene mutations that increase the risk of developing PD. It is particularly common in people of Ashkenazi Jewish, North African Arab Berber and Basque descent, and variants have also been found in Chinese and Japanese populations. This gene is also known as PARK8, denoting its link to Parkinson’s disease and the order in which it was found to have a connection to PD (8th). (common in certain ethnic groups, such as North African Arabs).
- Autosomal recessive: the presence of two altered copies of this gene is required to cause the disease. Examples include: PARK7, PINK1, PRKN.
- Risk factor modifiers genes: genes that modify the risk of developing Parkinson’s in some families. Examples include: GBA (makes the enzyme glucocerebrosidase).
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 PD 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 disease. Usually genetic testing is done for research purposes only.
The hope is that discoveries from research studies may open the door to new therapeutic targets for Parkinson’s 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 we encourage you to consult with a neurologist and a genetic specialist before you decide to proceed with any genetic testing for Parkinson’s disease.
Page reviewed by Dr. Ahmad Elkouzi, Movement Disorders Fellow at the University of Florida, a Parkinson’s Foundation Center of Excellence.