The Real Life of Ataxia Patients Without a Vertical Family History: a Twenty-year Experience in South Brazil

Studies of hereditary ataxias (HA) without vertical family history are necessary for designing diagnostic protocols. We described the 20 years' experience of a Brazilian reference service with these cases through a retrospective cohort study of subjects evaluated from 2002 to 2020 in a university hospital. Tests for Friedreich ataxia, alpha-fetoprotein, common dominant ataxias, and brain imaging were the first steps, whereas ataxia Sanger panel, exome or genome sequencings (NGS) were the last ones. The outcomes were: diagnosis; no diagnosis after NGS; or incomplete diagnostic investigation. Diagnoses and diagnostic yields were also presented. 174 subjects started investigation and 120 came to the second visit: 45/120 received a diagnosis, 12/120 finished their investigation without a diagnosis, and 63/120 were incompletely investigated. Higher-than-expected proportions of white subjects and of people coming from small communities were found. Most common diagnoses were Friedreich ataxia, ataxia-telangiectasia, Coenzyme Q10 deficiency, Niemann-Pick type C, ataxia with oculoapraxia type 2, and spinocerebellar ataxia type 2. Thirty-two subjects were investigated by NGS; among them, 5/7 ataxia Sanger panels, 9/17 exome and 1/7 genome sequencings got a molecular diagnosis, with diagnostic yields of 71.4%, 52.9% and 14%, respectively. The high proportion of patients lost to follow-up, cases with incomplete investigation and white individuals suggest problems in the access to healthcare. Exome and Sanger panels were the most efficient methods for reaching a diagnosis. The fact they are not easily available in the public health system is an important barrier to overcome, hopefully soon.