Is Parkinson disease inherited ?
Is Parkinson disease inherited? Most cases of Parkinson disease are classified as sporadic and occur in people with no apparent history of the disorder in their family. Although the cause of these cases remains unclear, sporadic cases probably result from a complex interaction of environmental and genetic factors. Additionally, certain drugs may cause Parkinson-like symptoms. Approximately 15 percent of people with Parkinson disease have a family history of the disorder. These familial cases are caused by mutations in the LRRK2, PARK2, PARK7, PINK1, or SNCA gene, or by alterations in genes that have not yet been identified. Mutations in some of these genes may also play a role in cases that appear to be sporadic. It is not fully understood how mutations in the LRRK2, PARK2, PARK7, PINK1, or SNCA gene cause Parkinson disease. Some mutations appear to disturb the cell machinery that breaks down (degrades) unwanted proteins. As a result, un-degraded proteins accumulate, leading to the impairment or death of dopamine-producing neurons. Other mutations may involve mitochondria, the energy-producing structures within cells. As a byproduct of energy production, mitochondria make unstable molecules, called free radicals, that can damage the cell. Normally, the cell neutralizes free radicals, but some gene mutations may disrupt this neutralization process. As a result, free radicals may accumulate and impair or kill dopamine-producing neurons. In some families, alterations in the GBA, SNCAIP, or UCHL1 gene appear to modify the risk of developing Parkinson disease. Researchers have identified some genetic changes that may reduce the risk of developing the disease, while other gene alterations seem to increase the risk.