Background: Adult onset dominant cerebellar ataxias (ADCAs) are a group of clinically and genetically heterogeneous, adult onset, autosomal dominant disorders, involving cerebellum or its connection and are clinically characterized by progressive cerebellar ataxia. Since phenotypic and genotypic diversity in ADCAs exist in a multiethnic country like India, genetic testing is necessary in order to find out the precise variety prevailing in a certain ethnic population.
Aim: To study the clinical features and genetic pattern of ADCAs in ethnic Bengalees of Eastern India.
Results: Clinical evaluation and genetic studies were carried out on 35 individuals belonging to 12 families consisting of 12 patients and 23 members of the families. There was overlap of clinical features amongst different ADCAs, as well as in phenotypic variations with the same genotype and repeat length within a family. Slow saccadic eye movements and peripheral neuropathy, found generally in genetically proven spinocerebellar ataxia (SCA) type 2, were also observed in SCA1 and SCA3 cases. No clinical feature could be found as exclusive to the different genotypes of SCA and we found that it was not possible to predict the genotype from studying the clinical profile.
Conclusion: Because of significant overlapping of clinical features among different genotypes of ADCAs, phenotypic expression is not a reliable marker for predicting the genotype. Genetic studies revealed that cases belonging to the SCA3 variety outnumber the other varieties of SCA, prevalent in India.