Repeat Expansions in a Chilean Cohort with Adult-Onset Cerebellar Ataxia

The diagnosis of hereditary ataxias caused by repeat expansions continue to present unique methodological challenges, especially for developing countries where genomic medicine services are not well established. The purpose of this work is to present a cohort of patients who presented with adult-onset ataxia of suspected genetic etiology, but had remained undiagnosed until now. They were analyzed for a set of repeat expansions including the genes causing the more recently identified types, SCA27BandRFC1-related CANVAS. Patients with a possible diagnosis of hereditary cerebellar ataxia with adult onset underwent genetic testing to detect a set of repeat expansions known to cause autosomal dominant ataxia. In selected cases, a complete vestibular function evaluation and brain magnetic resonance imaging was acquired. In 17 of the 56 studied cases (including 11 of 43 index cases) we established a genetic diagnosis, which demonstrates that this is a promising approach to adult-onset ataxias in a population that remains underrepresented in worldwide genomic studies. We identified 9 individuals with SCA27B and 7 with CANVAS, highlighting the epidemiological relevance of these newly recognized etiologies, an information useful for planning the allocation of resources towards improving the access to genomic medicine in in our region.