Prospective Multicenter Registry Study of Multiple System Atrophy in China

Inclusion Criteria 1. Patients with clinically established or clinically probable multiple system atrophy according to the 2022 Movement Disorder Society diagnostic criteria; or 2. Patients with clinically established or clinically probable Parkinson disease according to the Movement Disorder Society diagnostic criteria; or 3. Healthy controls or controls without hereditary or neurodegenerative diseases who voluntarily agree to participate. 4. Age between 40 and 75 years. 5. Ability to provide informed consent or availability of a legally authorized representative when applicable. Exclusion Criteria 1. Parkinsonism that cannot be classified as Parkinson disease or multiple system atrophy at the time of evaluation. 2. Clinical suspicion or diagnosis of other atypical parkinsonian syndromes, including progressive supranuclear palsy, dementia with Lewy bodies, or corticobasal syndrome. 3. Secondary parkinsonism due to intracranial space-occupying lesions, normal pressure hydrocephalus, drug-induced parkinsonism, or other identifiable causes. 4. Comorbid diseases that may substantially affect autonomic function, such as diabetic peripheral neuropathy or amyloidosis. 5. Refusal to participate in the study or refusal to undergo routine clinical evaluations for parkinsonian syndromes. 6. Psychiatric or behavioral abnormalities that preclude reliable clinical data collection or scale-based assessment.