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Huntington disease And other Chorea

What is Huntington disease?

  • HD is a progressive neurological condition caused from a genetic mutation in a particular segment of the Huntington (HTT) protein.The abnormal triple repeat mutation leads to an excessively long protein which causes many areas of dysfunction.

  • The mutation is passed on an autosomal dominant fashion which means that there is a 50/50 chance that the child will have the disease if he or she inherits one copy of the mutation.  If the child has not inherited this expanded gene, he or she will never develop the disease and cannot pass it on to their children.

  • In general, the disorder appears more severe the higher the number of repeats and with each generation (anticipation).

  • While great research is being performed for a cure for HD, there is no such cure at this time.

What are some of the symptoms of Huntington disease?

  • Affected individuals may have abnormal movements that appear dance-like and flow from one body part to the next (chorea).  Chorea can occur in the mouth, face, head, arms, legs, and trunk.

  • While chorea is the main movement that occurs, other movements such as stiffness (rigidity), slow movements (bradykinesia), sustained muscle contractions (dystonia), and sudden jerks (myoclonus) can also occur.  

  • Mood dysfunction (anxiety or depression) and personality changes

  • Cognitive dysfunction (impaired judgement, forgetfulness)

  • Weight loss

  • Hallucinations

  • Difficulty swallowing (dysphagia)

  • Gait/balance abnormalities

How is HD diagnosed?

  • After seeing your movement disorder specialist (MDS), a careful exam and history may reveal abnormal findings as above.

  • The patient is counseled about the risk of the disease and the risks of knowing whether or not the patient is affected.  

  • The patient's blood is then sent for genetic conformation for HD and number of repeats present in the mutated gene.  

How is HD treated?

  • In general, it truly takes a whole team to treat this disorder.

  • If patients have bothersome and excessive movements (such as chorea), then patients will often times take medications that deplete or block dopamine (tetrabenazine or an atypical anti-psychotic.)

  • Every medication has the potential for side effects and should further be discussed with the movement disorder specialist (MDS.)  

  • Medications such as melatonin and others can be given for sleep.  

  • Additional medications such as donepezil or memantine are given for cognitive dysfunction.  

  • The extent of the cognitive dysfunction may be evaluated by a neuropsychologist (a specially trained professional with extensive training on cognitive testing and interpretation.)

  • Physical therapy, occupational therapy, and speech therapy may all be utilized to treat the patient.  

  • Patients will often visit with the social worker to help easy caregiver burden and learn about resources available to the patient and the caregiver.  

What are other types of chorea?

  • Tardive chorea (choreiform movements that come on after prolonged exposure to metoclopramide or other agents that may block dopamine (such as some anti-depressants and anti-psychotics)

  • Infection-induced (ex: Sydenham's chorea)

  • Auto-immune (ex: rheumatoid arthritis, mixed connective tissue disease, lupus or SLE, anti-NMDA related movements)

  • Medication induced (ex: carbidopa/levodopa in Parkinson disease)

  • Cerebral palsy and other structural lesions of the brain

  • Neurodenerative diseases (ex: Wilson's disease, benign hereditary chorea, inherited ataxias or spinocerebellar ataxias)

How are these types treated?

  • Chorea is treated much the same as chorea in Huntington disease is treated, by depleting or blocking dopamine (tetrabenazine or neuroleptics such as risperidone.)

  • Depending on the cause of the chorea, other medications may be indicated such as immunosuppressing agents such as IVIG, steroids, or plasma exchange.  

  • If the chorea is drug-induced, stopping or weaning the offending agent is often the treatment of choice.

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