Observational StudyColonic Tissue Biopsy Detection of Phosphorylated Alpha-synuclein for Parkinson's Diagnosis or REM Sleep Behavior Disorder

Inclusion Criteria:

1. Relatively healthy men and women ≥40-99 years of age
2. Patients with a diagnosis of

1. Clinically confirmed PD or
2. Clinically confirmed RBD with no diagnosis of PD, DLB or MSA
3. Patients must have agreed to undergo a routine colonoscopy as part of their screening or surveillance for colon cancer or for diagnostic purposes for the exclusion of other GI diseases

Exclusion Criteria:

1. Use of anticoagulants (Plavix or aspirin alone is allowed)
2. Under active treatment for colon cancer; 30-day post anti-cancer treatment allowed
3. Current, ongoing gastrointestinal illness
4. Recent intrabdominal surgery
5. Pregnant or planning to become pregnant before the scheduled colonoscopy
6. Significant cognitive impairment, as determined by study investigators