ATXN3 and Parkinson disease: The most common SCA types include SCA1, SCA2, SCA3, and SCA6, caused by CAG tandem repeats in the ATXN1, ATXN2, ATXN3, and CACNA1A genes, respectively.1 SCAs involve damage to the cerebellum and cerebellar pathways.1 These structures have a regulatory role in motor activity,2 and their disruption leads to ataxia (movement incoordination) in SCA, a characteristic feature amongst other symptoms which implicate various functions and body systems (e.g. sleep disorder, vestibular dysfunction, parkinsonism, tremor, and fatigue)3-6.