Phosphorylated α-synuclein pathology in the diagnosis of synucleinopathies through qualitative and quantitative measurements of cutaneous phosphorylated α-synuclein in patients with Parkinson's disease, Multiple System Atrophy, Dementia with Lewy bodies and Pure Autonomic Failure. An effective tissue biomarker will provide an accurate diagnosis of α-synuclein in clinical practice, will differentiate between synucleinopathies, enable assessment of target engagement in the development of disease modifying and neuroprotective therapies and accelerate the development of neuroprotective and disease modifying therapies.