Parkinson’s disease (PD) is a that affects predominately dopamine-producing (“dopaminergic”) neurons in a specific area of the brain called the basal ganglia, where cells produce dopamine.

Symptoms generally develop slowly over years. The progression of symptoms is often a bit different from one person to another due to the diversity of the disease. People with PD may experience:

• Involuntary shaking of the hands, arms, legs, jaw or tongue. The typical Parkinson’s tremor is “pill-rolling” – it looks like holding a pill between thumb and forefinger and continuously rolling it around. Some people report an internal tremor, a shaking sensation inside the chest, abdomen or limbs that cannot be seen. Most Parkinson’s tremor is “resting tremor,” which lessens during sleep and when the body part is actively in use, mainly at rest and described as pill rolling tremor in hands. Other forms of tremor are possible
• Slowness of movement
• In Parkinson’s, stiffness of the arms or legs beyond what would result from normal aging or arthritis. Some people call it “tightness” in their limbs
• Gait and balance problems

The cause remains largely unknown. Although there is no cure, treatment options vary and include medications and surgery. While Parkinson’s itself is not fatal, disease complications can be serious.

(From: https://www.parkinson.org/understanding-parkinsons/what-is-parkinsons)