Relationship Between Immunosuppressive Treatment Status and Clinical Course of Parkinson's Disease

The goal of this observational study is to learn if immunosuppressive drug treatment influences the clinical course of Parkinson's disease. Recent research suggests that Parkinson's disease may have an inflammatory background. Numerous studies have identified elevated levels of pro-inflammatory markers in people with Parkinson's disease. Therefore, immunosuppressive drugs may potentially affect the course of this disease. The investigators will recruit people with Parkinson's disease, who receive long-term immunosuppressive treatment for other chronic illnesses, into the study group. The study will also recruit people with Parkinson's disease with no history of immunosuppressive drug treatment into the control group. The main question this study aims to answer is: \> Does immunosuppressive drug treatment slow down the onset and/or progression of Parkinson's disease? Researchers will compare Parkinson's disease progression rates and serum inflammatory marker levels between the study and control group, to see if immunosuppressive drug treatment influences the course of Parkinson's disease. The study requires each participant to attend one hospital appointment. This appointment will be approximately one hour long, and will involve: 1. clinical Parkinson's disease motor assessments conducted by the research team -\> participants will be evaluated in the OFF state, meaning they will not have taken their Parkinson's disease medication the day of the assessment; 2. completion of Parkinson's disease symptom scales; 3. a one-time serum sample collection; 4. detailed medical history obtainment from the participant by the research team, with a primary focus on the patient's immunosuppressive treatment history and individual clinical course of Parkinson's disease.