Parkinson's disease affects about 500,000 Americans, with 50,000 new cases diagnosed each year, according to the National Institute of Neurologic Disorders and Stroke. Parkinson's disease occurs when nerves in the portion of the brain known as the substantia nigra become damaged and no longer produce a necessary chemical called dopamine. Loss of dopamine causes abnormal nerve signaling, resulting in the characteristic symptoms of tremors, difficulty walking, balance problems and muscle rigidity. Doctors often cannot pinpoint the exact cause of the disease because many factors contribute to its onset.
Lewy Bodies
A Lewy body describes an abnormal clump of proteins. Many patients with Parkinson's disease have Lewy bodies in their brain cells. Although the reason why Lewy bodies form remains unclear, their presence interferes with brain cell functioning and contributes to the development of Parkinson's disease, as described by the National Institute of Neurologic Disorders and Stroke.
Genetic Mutations
A genetic disease occurs when a gene--a segment of deoxyribose nucleic acid, or DNA--containing a mutation passes from parent to child. Although scientists have identified 13 genes associated with Parkinson's disease as of 2010, according to the Parkinson's Disease Foundation, only approximately 5 percent of patients with Parkinson's have the inherited form of the disease. The presence of certain genetic mutations, however, may only make a person more susceptible to the disease, which will still require an environmental trigger in order to develop.
Environmental Factors
Exposure to environmental toxins, such as a synthetic narcotic agent known as MPTP, may trigger the development of Parkinson's disease. MPTP, a common chemical found in herbicides and pesticides, can damage cells when ingested into the body. The Parkinson's Disease Foundation reports that rural living and drinking well water increases the exposure to pesticides, which in turn increases the risk of developing Parkinson's disease.
Viral Infections
Contracting some types of viral infections may also contribute to the onset of Parkinson's disease. Viruses trigger the cells of the immune system to react, resulting in inflammation. As the virus travels through the bloodstream, it can affect cells throughout the body, including the cells in the brain. Inflammation of the brain cells may cause them to die or change their programming that will make them susceptible to additional environmental factors that can later result in the onset of Parkinson's disease, as described by the Collaborative on Health and the Environment.
