A 60 year old male presents with features of atypical parkinsonism in conjunction with cerebellar signs and early and prominent autonomic dysfunction, usually ohostatic hypotension is MOST likely suffering from:

Multiple-system atrophy (MSA) manifests as a combination of parkinsonian, cerebellar, and autonomic features. Clinically, MSA is suspected when a patient presents with atypical parkinsonism with cerebellar signs and early autonomic dysfunction, usually ohostatic hypotension. Ref: Harrisons Principles of Internal Medicine, 18th Edition, Page 3318