Phenotype and genotype features of 187 patients with spinocerebellar ataxia type 3

Objective To discuss the genotype and phenotype features of 187 patients with spinocerebellar ataxia type 3 (SCA3) and analyze their genotype-phenotype relationship. Methods A total of 187 patients genetically diagnosed as having SCA3 from 160 families were enrolled from our hospital from 2005 to 2015. Detailed medical histories were collected. SPSS 22.0 was conducted to statistically analyze the genotypes and pathogenic CAG expansions of ATXN3 gene in the patients. Results One hundred males and 87 females suffered SCA3. Mean age at onset was 35.43±11.17 years. The ranges of pathogenic CAG expansion were 65-86 repeats, with mean pathogenic CAG expansion of 74.11±3.56 repeats. A negative correlation was found between number of CAG repeats and age of onset (r=-0.815, P=0.000). Frequencies of the patients with tendon hyporeflexia were 28.9% and 6.0%, respectively, in the smaller pathogenic CAG expansion group (≤74) and larger pathogenic CAG expansion group (>74), with significant difference (P<0.05). Frequencies of patients with rigidity were 27.8% and 49.4%, respectively, in the smaller pathogenic CAG expansion group and larger pathogenic CAG expansion group, with significant difference (P<0.05). Conclusions SCA3 is neurodegenerative disorder with high clinical and genetical heterogeneity. There are distinct correlations between number of pathogenic CAG expansion and age of onset, frequency of hyporeflexia and rigidity. Key words: Spinocerebellar ataxia type 3; ATXN3 gene; Phenotype; Genotype-phenotype relationship