Huntington’s disease

Huntington disease (HD) is a rare neurodegenerative disorder of the central nervous system characterized by unwanted choreatic movements, behavioral and psychiatric disturbances and dementia. It is genetically transmitted as an autosomal dominant trait with complete penetrance and thus has an equal likelihood of affecting males and females.

About 30,000 Americans — one in every 10,000 — have Huntington’s. More than 200,000 individuals are known to be at risk because they have a parent with the disease.

The first description by Waters, of a patient with what we now call Huntington’s chorea, dates from 1842. But it was not until 1872, after the lecture and description of the disease by George Huntington, that it became known as Huntington’s chorea.

Huntington's disease is associated with both involuntary and voluntary movement disorder which progressively worsens over the course of the disease. Characteristic abnormal involuntary movements involve limb choreoathetosis, most conspicuous in the upper extremities and appearing as a random jerky movement or a slow and sinuous writhing.

Huntington’s also causes a decline in thinking and reasoning skills, including memory, concentration, judgment and ability to plan and organize.

HD symptoms do not usually start until adulthood – 30’s and 40’s is most common. Some people with the HD gene expansion develop mood or cognitive changes first, and then later develop chorea and movement symptoms.

HD is an autosomal dominant inherited disease caused by an elongated CAG repeat (36 repeats or more) on the short arm of chromosome 4p16.3 in the Huntingtine gene. This defect is “dominant,” meaning that anyone who inherits it from a parent with Huntington’s will eventually develop the disease.
Huntington’s disease

Notes:
CAG (cytosine (C), adenine (A), and guanine (G)), is a trinucleotide, the building stone of DNA.