What is the difference between Parkinson's disease and parkinsonism?

Parkinsonism is a generic term for a group of symptoms that can be seen in someone with Parkinson's disease such as tremor, stiffness, and slowness of movement. There are several conditions other than Parkinson's disease which can cause these symptoms. Parkinson disease is a specific disease process leading to these symptoms. A neurologist determines the cause of parkinsonism by taking a careful history, performing an examination, and sometimes by ordering blood tests or imaging procedures such as MRI.