Spinocerebellar Ataxia type 3 is rare in the Peruvian Population

Abstract Spinocerebellar ataxia type 3 or Machado-Joseph Disease (MJD/SCA3) is the most prevalent autosomal dominant cerebellar ataxia worldwide, but its frequency varies by geographic region. We describe MJD/SCA3 patients diagnosed in a tertiary healthcare institution in Peru. In a cohort of 341 individuals with clinical ataxia diagnosis, seven MJD/SCA3 probands were identified and their pedigrees extended, detecting a total of 18(5%) MJD/SCA3 cases. Out of 682 alleles from this cohort, the 23-CAG repeat was the most common ATXN3allele (32.1%), followed by the 14-CAG repeat allele (26%). Normal alleles ranged from 12 to 38 repeats while pathogenic alleles ranged from 61-75 repeats. We identified 101 large normal (LN) alleles (14.8%). Five out of seven families declared an affected family member traced back to foreign countries (England, Japan, China, and Trinidad and Tobago). MJD/SCA3 patients showed ataxia, accompanied by pyramidal signs, dysarthria and dysphagia as well as abnormal oculomotor movements. In conclusion, ATXN3 allelic distribution in non-MJD/SCA3 patients with ataxia is similar to the distribution in normal individuals around the world, whereas LN allele frequency reinforces no correlation with the frequency of MJD/SCA3. Evidence of an abnormal MJD/SCA3 phenotype was not found. Further haplotypes are required to confirm the foreign origin of MJD/SCA3 in the Peruvian population.