People with Friedreich’s ataxia (FA) in South Brazil exhibited clinical symptoms similar to patients in Europe, although FA has a much lower prevalence in Brazil, according to researchers.
Their study, “Friedreich Ataxia: Diagnostic Yield and Minimal Frequency in South Brazil,” was published in the journal The Cerebellum.
Friedreich’s ataxia is a genetic disease that’s caused by mutations in the FXN gene, generally due to long repeats of the DNA sequence GAA.
The characteristic symptoms of FA, which start before the onset of puberty, include ataxia (lack of voluntary coordination of muscle movements), areflexia (absent reflexes), and Babinski sign (a normal reflex that occurs after the sole of the foot has been firmly stroked).
The prevalence of FA can range from between 1 in 50,000 to 0.13 in 100,000 in populations from Europe or in people with European ancestry. But in countries in Asia or Latin America, the prevalence is much lower. In fact, the estimated prevalence of Friedreich’s ataxia in Cuba is only 0.045 in 100,000.
So far, there have been no published reports that estimate the frequency of Friedreich’s ataxia in Brazil.
Researchers conducted a study to determine the prevalence of FA among ataxia patients in Rio Grande do Sul, South Brazil. Researchers set out to report the clinical findings, as well as to estimate the minimal prevalence of FA in this region.
Patients who were evaluated by molecular analysis for FA at the Hospital de Clínicas de Porto Alegre were identified, and then the patients’ clinical manifestations and symptoms were described and compared.
Since 1997, Friedreich’s ataxia was suspected in 156 cases, which were submitted for genetic analysis (GAA repeats in the FXN gene). Among this group, only 27 were confirmed as having FA, giving a diagnostic yield of 17.3%.
Patients in this study had a similar proportion of all symptoms — including classic, late-onset, and retained reflexes — compared to those described in other studies.
Additionally, the minimum prevalence was estimated to be 0.20 in 100,000 inhabitants.
“We verified that this [FA] population displayed the usual clinical characteristics, but with a lower period prevalence than those obtained in populations from Europe,” researchers wrote.
They said the diverse prevalence is likely due to the fact that the GAA expansion is carried mostly by individuals of European ancestry.
But they added that additional studies “on ancestral origins of FXN [gene copies] in South Brazil are required to clarify the reasons for these differences. Those studies will probably help to confirm the low frequency of [Friedreich’s ataxia] in this population.”