In collaboration with approximately 8 centers that specialize in iRBD we will recruit a total of 80 individuals for the study. All subjects will be enrolled into a 2-year longitudinal study where skin biopsies will be performed at 3 sites on each patient at 12-month intervals (baseline, year 1, year 2). Plasma blood collection will be performed at 12-month intervals (baseline, year 1, year 2). Detailed quantified examination, cognitive evaluation, medical history, and questionnaires will be performed at each visit. Additional biomarker, imaging and clinical information (if available) will be obtained for the purpose of determining phenoconversion to clinically apparent synucleinopathy.

Subjects enrolled in the study will have baseline evaluations and follow up visits at 12 and 24 months to define any changes to clinical diagnosis (clinical phenoconversion). Skin biopsies will be repeated at the 12- and 24-month follow up visits to determine the rate of P-SYN accumulation over time and the rates of nerve fiber degeneration within punch skin biopsies.

Inclusion Criteria:

1. Males and females age 18-85
2. Subjects will have repeated episodes of sleep related vocalizations and/or complex motor behaviors
3. Sleep-related behaviors/disturbances must be documented by polysomnography to occur during REM sleep
4. Polysomnographic recording is consistent with REM sleep without atonia

Exclusion Criteria:

1. Subjects with MoCA < 19, Hoehn and Yahr score >/=1, contraindications to skin biopsy

2. Diagnosis of Parkinson's disease

3. Diagnosis of dementia of any type

4. Diagnosis of multiple system atrophy

5. REM sleep behaviors/disturbances secondary to another cause (e.g., narcolepsy, dementia, and Parkinson's disease)

6. Contra-indications to skin biopsy:

   1. Clinical evidence of severe vascular disease (history of ulceration, poor wound healing, and vascular claudication)
   2. History of allergic reaction to local anesthesia for skin biopsies
   3. Use of blood thinners (aspirin of Plavix alone is allowed)
   4. Significantly impaired wound healing or history of scarring or keloid formation

Gender at birth

80 subjects diagnosed with iRBD