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Huntington ’s chorea
Intro:
Huntington’s disease, also known as Huntington’s chorea, is an inherited neurodegenerative
disease which leads to nerve cell degeneration in the brain. Although it is typically first observed
around the ages of 35-44, it can affect individuals at any stage in their lives. HD affects muscle
coordination, has behavioral symptoms, and ultimately leads to cognitive decline.
Symptoms:
Onset of Huntington’s symptoms typically occurs between the ages of 35-44, but can occur at
much earlier or later stages of life. The first symptoms include personality, cognitive and
physical skill changes. The typical characteristic physical signs are unintentionally initiated
motions, restlessness, lack of coordination, and slowed eye movements. As the disease
progresses, psychomotor functions decline and muscle control is severely affected. Patients have
trouble chewing, swallowing, and even talking. Some people have also reported issues with
apathy, psychosis, irritability, aggression, compulsive behaviors, cognitive thinking, trouble
planning, and even memory loss. Many people also experience anxiety and depression, at times
even leading to suicide. In the later stages it affects other brain regions and leads to severe
cognitive decline and dementia. Other related complications often arise such as pneumonia, heart
problems, or physical injuries leading to death. Life expectancy is on average 20 years from
onset of symptoms, but varies with age of onset and disease severity.
Genetics:
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Huntington’s disease is one of several tri-nucleotide repeat disorders and is an autosomal
dominant disease with 100% penetrance. The disease is caused by the Huntingtin gene which
codes for the Huntingtin protein. A CAG triplet repeat expansion within the Huntington gene
causes a mutant form of the wild type protein, and a person with 40 or more mutations is
considered a fully penetrant individual. Additionally, this person’s children will have a 50%
chance of expressing the disease. This triplet repeat mutation results in permanent damages to the
brain which is still not thoroughly understood and is still being studied.
Neurological Process:
Huntington’s disease is caused by degeneration in the basal ganglia. The striatum, the largest part
of the basal ganglia, is associated with movement control and addiction. In this disease,
