The Syn-D Study will be evaluating α-synuclein in patients with suspected MCI-AD and MCI-DLB. Using a simple diagnostic test will improve clinical accuracy in diagnosing, earlier diagnosis, and distinguish between neurodegenerative diseases.

In collaboration with approximately 10 centers that specialize in DLB and dementia we will recruit a total of 80 individuals for the study: 40 subjects with suspected MCI-DLB and 40 with suspected MCI-AD will be recruited. All subjects will be enrolled into a 12 month longitudinal study where skin biopsies will be performed at 3 sites on each patients at 12 month intervals (baseline and 1 year). Detailed quantified examination, cognitive evaluation, history, and questionnaires will be performed at each visit and will be reviewed by a central panel of disease experts to confirm the diagnosis.

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

Inclusion Criteria:

1. Men and women 50 to 85 years of age
2. Clinical diagnosis of mild cognitive impairment, and a presumed etiology of DLB or AD at enrollment

Exclusion Criteria:

1. Clinical evidence of severe peripheral vascular disease (Fazekas score of ≥ 3, or a large vessel stroke of ≥ 2 cm, history of ulceration, poor wound healing, vascular claudication)
2. Clinically active coronary artery or cerebrovascular disease
3. Current smoker or alcoholism
4. History of allergic reaction to local anesthesia (for biopsy collection)
5. Use of anticoagulants (aspirin or Plavix alone is allowed)
6. Significantly impaired wound healing or history of scarring or keloid formation

Sex is determined by gender at birth.

The subjects evaluated in the protocol will have a diagnosis of mild dementia with Lewy bodies (MCI-DLB) or mild Alzheimer's disease (MCI-AD). Patients will be evaluated at Baseline and 12 months. A total of 80 individuals will be enrolled, 40 with MCI-DLB and 40 with MCD-AD, with roughly equal representation of men and women.

All subjects will undergo screening evaluation that includes a thorough medical history, physical and neurologic examination and review of available medical records, laboratory studies, neuroimaging and sleep laboratory studies.

IPD will be shared with researchers that are involved in the study.