The SCA3 is an autosomal dominant heterogeneous neurodegenerative disorder characterized with gait ataxia, dysarthria and parkinsonism. Is the most common SCA worldwide, however only few cases were reported in Africa.

To clinically characterize families with SCA3 and identify the underlying genetic defect.

Patients with ataxia were examined in our Neurogenetics Clinic. DNA was collected from probands for genetic analysis. Brain imaging and blood chemistries were performed to exclude common causes.

287 families with a wide range of neurodegenerative were enrolled, and 177 patients presented with autosomal dominant ataxia. The gene panel testing showed CAG repeats in the ATXN3 gene in 4 probands. The mean age of onset was 29 years ranging from 10 to 59, anticipation has been noted in all families. The mean age at diagnosis was 43 years. For the genetic testing the average of CAG was 73 repeats, the four probands had cerebellar atrophy on the brain imaging.

We found a positive correlation between age of onset and CAG repeat numbers. Studying families with high number of affected sibs will allow refine or consolidate the natural history of these diseases. The haplotype studies may establish the origin of these mutations. We identified a penetrance in the different families, a very few cases (2) of non-penetrance are known, the MJD is considered fully penetrant.

We identified three families with SCA3; confirming that this disease is not uncommon in sub-Saharan Africa. Studying families with high number of affected sibs will allow refine or consolidate the natural history of these diseases.

This study was funded by the NIH through H3Africa project. There was no conflict of interest in this study.