Research Into the Expression of the csgA-gene and How it Changes in Patients With Parkinson's Disease

Inclusion Criteria: * Between 18-80 years of age at ICF signing (inclusive) * A diagnosis of PD within 10 years from the time of ICF signing * Current or history of gastrointestinal (GI) dysfunction or constipation based on screening assessment * All participants must understand and provide written informed consent prior to any study specific procedures * Able to speak, read, and understand study procedures in Dutch sufficiently to allow completion of all study assessments Exclusion Criteria: * Any known GI disorder if deemed clinically significant by the investigator. GI disorders may include, but are not limited to: Crohn's disease, ulcerative colitis, celiac disease, irritable bowel syndrome, or lactose intolerance * Recent GI infection in the past 3 months if deemed clinically significant by the investigator. * Major GI surgery (excluding appendectomy/cholecystectomy), such as bariatric surgery, gastrectomy, esophagectomy, vagotomy, small intestine surgeries, any type of colectomy, colostomy and anorectal surgeries if deemed clinically significant by the investigator * Any known current or past eating disorder if deemed clinically significant by the investigator * Use of systemic antibiotics within 6 months prior to enrollment