How Parkinson’s disease is inherited is unclear. The majority of people who are diagnosed with Parkinson’s have no family history of the disease. Only in rare cases does Parkinson’s disease run in families. The Parkinson’s Disease Society estimates that five percent of Parkinson’s cases are hereditary, while the U.S. National Library of Medicine estimates the number to be much higher at 15 percent.
Certain genes that contain mutations have been identified in Parkinson’s patients who have a familial history of the disease, which are believed to make a patient more susceptible to getting Parkinson’s. Presence of the genes does not guarantee that a person will get the disease; instead, the genes present a susceptibility to developing Parkinson’s. The National Human Genome Research Institute lists seven genes that have been identified to have mutations in hereditary cases of Parkinson’s: SNCA (PARK1), UCHL1 (PARK 5), LRRK2 (PARK8), (PARK3), PARK2 (PARK2), PARK7 (PARK7) and PINK1 (PARK6). Some of the mutated Parkinson’s genes are passed down in an autosomal dominant pattern, meaning only one copy of the gene needs to be inherited. Other genes are passed in an autosomal recessive pattern, meaning two copies of the mutated genes must be inherited.
Originally, Parkinson’s disease was thought to be purely caused by environmental factors. In cases where there is no family history of the disease, environmental factors alone may be responsible for Parkinson’s. When mutated Parkinson’s genes are present, environmental factors are thought to play at least a partial role in the onset of the disease. Exposure to pesticides and insecticides, deficiencies in folate, head traumas, neck traumas and low estrogen levels in women are believed to increase the risk of Parkinson’s. It is important to remember that exposure to these environmental factors does not mean a person will get Parkinson’s disease.
There is some evidence that antioxidants may help prevent the onset of Parkinson’s disease in high-risk people and reduce the progression of Parkinson’s in people who have the disease. Some of the antioxidants being researched for Parkinson’s are coenzyme Q10, choline, L-tyrosine, Omega-3 fatty acids, creatine and vitamins, B, C, D and E.
Genetic testing can detect some types of mutated Parkinson's genes. The benefits of genetic testing for Parkinson's are limited. Having the genes does not necessarily mean that a person will get Parkinson's, and not having the genes does not mean that person will not get Parkinson's.