What is (are) Parkinson disease ?
Parkinson disease belongs to a group of conditions called movement disorders. The four main symptoms are tremor, or trembling in hands, arms, legs, jaw, or head; rigidity, or stiffness of the limbs and trunk; bradykinesia, or slowness of movement; and postural instability, or impaired balance. These symptoms usually begin gradually and worsen with time.  As they become more pronounced, patients may have difficulty walking, talking, or completing other simple tasks.  Not everyone with one or more of these symptoms has Parkinson disease, as the symptoms sometimes appear in other diseases as well. Parkinson disease affects about 1 to 2 percent of people over the age of 60 years and the chance of developing Parkinson disease increases as we age. Although some Parkinson disease cases appear to be hereditary most cases are sporadic and occur in people with no apparent history of the disorder in their family. When three or more people are affected in a family, especially if they are diagnosed at an early age (under 50 years)  there may be a gene making this family more likely to develop the condition. Currently, seven genes that cause some form of Parkinson's disease have been identified. Mutations (changes) in three known genes called SNCA (PARK1),UCHL1 (PARK 5), and LRRK2 (PARK8) and another mapped gene (PARK3) have been reported in families with dominant inheritance. Mutations in three known genes, PARK2 (PARK2), PARK7 (PARK7), and PINK1 (PARK6) have been found in affected individuals who had siblings with the condition but whose parents did not have Parkinson's disease (recessive inheritance). There is some research to suggest that these genes are also involved in early-onset Parkinson's disease (diagnosed before the age of 30) or in dominantly inherited Parkinson's disease but it is too early yet to be certain. However, in most cases inheriting a mutation will not cause someone to develop Parkinson's disease because there may be additional genes and environmental factors determining who will get the condition, when they get it and how it affects them.