Abstract
Objective: To evaluate the clinical and genetic characteristics of a large group of people affected by spinocerebellar ataxia type 3 (SCA3), also known as Machado-Joseph disease (MJD). Methods: 211 SCA3/MJD patients were characterized according to sex, age of disease onset, number of CAG repeats in the expanded allele, subtype, sex of the parent from whom the disease was inherited, anticipation of signs and symptoms and percentage of affected offspring. Results: We observed that larger CAG expansions, subtype 1 of the disorder and the patient’s gender influence the earlier onset of the disease. Male developed the signs and symptoms of SCA3/MJD four years earlier than female. The mean age at onset in patients was 4.84 years earlier than the mean age at onset of their parents, indicating anticipation. In addition, it was observed that the paternal anticipation was 7.19 years while the maternal was 3.57 years. Conclusion: This SCA3/MJD population shows some peculiarities, especially in relation to the different ages of onset between male and female. The recognition of factors that modify the age of onset of the disease and the way they interfere in the affected population can contribute to the future management of this condition.