Parkinson's disease is due to the lack of production of a chemical called dopamine, which produces the brain. Dopamine is one of the mood of the people, and also is responsible for controlling the movements of our body. The lack of dopamine causes signs and symptoms that appear progressively. That's why it sometimes is difficult to diagnose the disease at an early stage.
The World Health Organization (who) set April 11 as the World Parkinson day in 1997, and on this day commemorates the day of all those affected by Parkinson's disease.