Spinocerebellar ataxia type 3 (SCA3), commonly known as Machado–Joseph disease, is an autosomal dominant neurodegenerative ataxia initiated by expanded cytosine–adenine–guanidine (CAG) triplet repeats in the coding region of ATXN3, specifically located at chromosome 14q32.1 [1]. The gene discussed is ATXN3; the disease is Machado-Joseph disease.