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Updated: May 5 2022

Huntington Disease

  • Snapshot
    • A 20-year-old man presents with a two-year history of motor restlessness that has progressed to uncontrollable choreiform movements. He has moderate dementia with a severe gait disturbance as well as agitation and problems with his mood. CT scan of the brain shows atrophy of the cerebral cortex and caudate nucleus.
  • Introduction
    • An autosomal dominant disorder characterized by
      • choreiform movements
      • progressive intellectual deterioration
      • exhibits genetic anticipation
    • Epidemiology
      • demographics
        • symptoms usually begin to appear in the 3rd-5th decade of life
        • both sexes are affected equally
      • incidence
        • 0.38 cases per 100,000 per year
    • Genetic
      • inheritance
        • autosomal dominant
      • mutation
        • CAG triplet repeat expansion in huntingtin gene (chromosome 4)
          • HUNT 4 an animal, put it in a CAGe
        • demonstrates anticipation
        • mutation leads to atrophy of striatum (especially caudate nucleus) with neuronal loss and gliosis
        • decrease in the levels of GABA and ACh
    • Pathophysiology
      • changes in neurotransmitters with Huntington's disease
        • ↑ dopamine (in ventral tegmentum and substantia nigra) and ↓ GABA (in nucleus accumbens) and ACh (in basal nucleus of Meynert)
          • high dopamine can act on the nigro-striatal pathway to result in hyperkinesis
          • high dopamine can act on the meso-limbic pathway to result in psychotic symptoms
  • Presentation
    • Symptoms
      • progressive choreiform movements of all limbs
      • ataxic gait
      • dementia
      • depression
      • grimacing
  • Evaluation
    • MRI
      • shows atrophy of caudate
  • Treatment
    • Pharmacologic
      • no known cure
      • medications used to treat Huntington's disease include
        • amine-depleting agents (inhibit VMAT, involved in monoamine transport)
          • reserpine
            • ↓ release of amines (dopamine)
          • tetrabenazine
            • ↑ degradation of amines (dopamine)
        • antipsychotics
          • haloperidol
            • dopamine receptor antagonist
            • ↓ effect of excess dopamine resulting in psychotic symptoms
            • antipsychotics
        • muscle relaxants
          • benzodiazepines
  • Prognosis, Prevention, and Complications
    • Death inevitable
    • Suicide common cause of death
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