Spinocerebellar ataxia type 3 (SCA3), also known as Machado-Joseph disease, is the most common SCA subtype worldwide and is caused by abnormal CAG trinucleotide repeats (52–86) in ATXN3 gene encoding for the Ataxin3 protein [9, 27]. The gene discussed is ATXN3; the disease is Machado-Joseph disease.