[Direct genetic diagnosis in Huntington's chorea].

Huntington's disease is a late manifesting autosomal dominant neurodegenerative disorder. It is characterized by motor disturbance, loss of cognitive functions and psychiatric manifestations. Recently, the disease causing mutation, an unstable DNA sequence in the coding region of the Huntington gene on chromosome 4p, has been identified. A trinucleotide (CAG) repeat is expanded over the normal range and can easily be detected by standard laboratory methods. Accurate genetic testing can now be offered in clinically questionable cases and to subjects at risk for Huntington's disease. Furthermore, there seems to be a correlation between the size of the expanded CAG repeat and the age of onset in affected individuals. We have investigated more than 130 individuals from different affected families and illustrate the advantages and the clinical application of the new method.