[Huntington's chorea: clinical aspects, genetics and current diagnosis]

Area of Science:

• Neurogenetics
• Molecular Biology

Context:

• Huntington's disease is a late-onset, autosomal dominant neurodegenerative disorder.
• Characterized by motor, cognitive, and psychiatric symptoms.
• The genetic mutation involves an unstable trinucleotide [CAG] repeat expansion in the Huntington gene.

Purpose:

• To discuss the identification and implications of the Huntington gene mutation.
• To highlight the role of genetic testing in diagnosis and risk assessment.
• To explore the correlation between CAG repeat size and age of onset.

Summary:

• The mutation is an expanded CAG trinucleotide repeat in the Huntington gene, detectable by standard methods.
• Genetic testing is available for diagnosing questionable cases and screening at-risk individuals.
• A correlation exists between expanded CAG repeat size and age of onset, though predictive value is limited.
• Expanded repeats show instability, particularly in male meiosis, potentially explaining anticipation and juvenile cases.

Impact:

• Accurate genetic testing can now be offered to presymptomatic individuals.
• Understanding repeat instability sheds light on disease anticipation and new mutations.
• Provides a basis for future research into Huntington's disease mechanisms and potential therapies.