Huntington's disease

Inherited progressive chorea and dementia in middle life (CAG repeats)

Prevalence

• 5:100000

Aetiology

• Autosomal dominance with full penetrance
• Children of an affected parent have a 50% chance of inheriting the mutation on chromosome 4

Pathology

• Cerebral atrophy
• Loss of neurones in caudate nucleus and putamen
• Depletion of gamma-aminobutyric (GABA), angiotensin-converting enzyme (ACE) and met-enkephalin in substantia nigra

Clinical features

• Chorea (Sudden involuntary jerky semi-purposeful movements, flitting from one part of the body to another)
• Progressive dementia

Investigations

• MRI or CT shows atrophy or caudate nucleus

Management

• Phenothiazines may reduce chorea

Prognosis

• Death 10-20 years after onset

Screening

• Mutation analysis is available for presymptomatic screening in families but no effective treamtent is known to alter disease progression

Other causes of chorea

• Sydenham's chorea (rheumatic fever)
• Drugs, e.g. phenytoin
• Thyrotoxicosis
• Stroke
• Systemic lupus erythematosus (SLE)