Parkinson's disease -

Parkinson's disease is a neurodegenerative disorder, which leads to progressive deterioration of motor function due to loss of dopamine-producing brain cells. The cause of Parkinson’s Disease is unknown, but researchers speculate that both genetic and environmental factors are involved. Some genes have been linked to the disease.

Primary symptoms include -
Tremor
Stiffness
Slowness
Impaired balance and later on a shuffling gait

Some secondary symptoms include -
Anxiety
Depression, and dementia.
Most individuals with Parkinson's disease are diagnosed when they are 60 years old or older, but early-onset Parkinson's disease also occurs.