Test Details: SCA3 (Machado-Joseph disease) is an autosomal dominant ataxia being one of the most common among majority of populations. It is classified into 3 types namely- Type I (Amyotrophic lateral sclerosis-Parkinsonism-Dystonia type); Type II (Ataxic type) & Type III (Ataxic-Amyotrophic type). Mean age of onset of SCA3 is 25 years and patients have severe debilitation by 15 years from the age of onset in types I & II. In SCA 3 there is an expansion in CAG trinucleotide repeat in chromosome 14q which results in abnormal Ataxin-3 protein production.