RESUMO
The authors present a historical review of spinocerebellar ataxia type 3/Machado-Joseph disease (SCA3/MJD), the most common form of spinocerebellar ataxia in Brazil, and consider the high frequency of cases in families from Itajaí, a city on the coast of the state of Santa Catarina with a large population of Portuguese/Azorean descent.
Assuntos
Doença de Machado-Joseph/história , Brasil/etnologia , Família , História do Século XVIII , História do Século XX , Humanos , Doença de Machado-Joseph/etnologiaRESUMO
ABSTRACT The authors present a historical review of spinocerebellar ataxia type 3/Machado-Joseph disease (SCA3/MJD), the most common form of spinocerebellar ataxia in Brazil, and consider the high frequency of cases in families from Itajaí, a city on the coast of the state of Santa Catarina with a large population of Portuguese/Azorean descent.
RESUMO Os autores apresentam uma revisão histórica sobre a ataxia spinocerebelar tipo 3/doença de Machado-Joseph (SCA3/DMJ), que representa a forma de SCA mais comum em nosso país, considerando a alta frequência de casos oriundos de famílias da cidade de Itajaí, no litoral de Santa Catarina, cidade com ascendência portuguesa-açoriana.
Assuntos
Humanos , História do Século XVIII , História do Século XX , Doença de Machado-Joseph/história , Brasil/etnologia , Família , Doença de Machado-Joseph/etnologiaRESUMO
Spinocerebellar ataxia type 3 is the most common form of autosomal dominant cerebellar ataxia. It is a severe progressive neurological disorder caused by an expansion of an exonic CAG repeat of the MJD1 gene. The repeated sequence is polymorphic among both normal individuals and patients. In general, expanded alleles are paternally inherited and the disorder exhibits anticipation. We performed a PCR-based study to determine polymorphisms of the number of CAG repeats of the MJD1 gene in an anonymous sample of normal Brazilian individuals. We also analyzed DNA samples from 9 patients with ataxia. We identified 29 different allele sizes ranging from 12 to 40 CAG repeats, with heterozygosity of 79%. The distribution of allele sizes showed two major peaks of 16 (7%) and 26 (10.1%) CAG repeats. When grouping normal alleles by size, we observed that the distribution varies between males and females, and a significant deviation from the Hardy-Weinberg equilibrium was observed with an excess of normal large alleles among males. We also detected expanded alleles with 68-73 CAG repeats in 3 out of 9 ataxic patients.