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July 6, 1998
History of Huntington's Disease
Huntington's disease (also known as Huntington's chorea) is a debilitating neurological disorder that causes progressive degeneration of neurons in the basal ganglia. It is very much a familial disorder, both because of its inherited nature, and also because of the toll it takes, not only on the patient, but on the family that endures their slow decline from this fatal genetic disease.
In this feature, I will give some background on the disease, and what is known about its etiology. I will also discuss some of the history of the disease, especially its early descriptions.
Features of the Disease
Throughout Europe and North America, the incidence of HD is approximately five to eight per 100,000. About 30,000 Americans have Huntington's Disease symptoms and another 150,000 have a 50% risk of carrying the gene that is responsible for the disease. All of those who carry the gene are likely to show signs of the disease by the third or forth decade of life.
Most Huntinton's patients present with a movement disorder known as a chorea consisting of facial twitching or a twitching or restlessness of the distal extremities. As the disease progresses over 10 to 25 years, the movement disorder becomes more generalized eventually impairing gait. Rigidity and dystonia predominate in later stages of the disease. Many patients, especially late in the course of the disease will have some form of mental deterioration, or even psychotic symptoms, and depression in these patients is also common. A minority of patients will first present with psychiatric symptoms, perhaps experiencing mood swings or becoming uncharacteristically irritable, apathetic, passive, depressed, or angry.
The Cause of Huntington's Disease
Huntington's Disease is inherited as an autosomal dominant disorder with complete penetrance resulting from a mutation on chromosome 4. The nature of the mutation is an expansion of CAG repeats at the end of the gene. Although the nature of the gene product (the protein huntintin) is not fully understood, it is known to be expressed ubiquitously and needed for normal cell survival. The expansion of the CAG repeats causes a region of polyglutamine on the huntintin protein that enhances the function of a cysteiene protease called apopain. Since this protease is known to play a role in apoptosis (a type of programed cell death), it is thought that the huntinin mutation leads to inappropriate apoptosis, and destruction of cells. Why this cell destruction is differentially targeted to the basal ganglia and cerebral cortex is not understood.
History
The word chorea comes to us from the Greek, by way of Latin and means dance. It's application to the class of movement disorders involving destruction of the basal ganglia describe the rhythmic, writhing movements that are, for the most part, uncontrollable by the afflicted individual. It was Paracelsus (1493-1541) who first used the term to define these movement disorders. He described three choreas one of which was chorea naturalis - where patients "only felt an involuntary impulse to ally the internal disquietude." It is thought by some researchers that this may have been the same as HD.
The first very thorough treatment of chorea was presented by Thomas Sydenham (1624-1689), a British physician. A childhood chorea, distinct from Huntington's disease and associated with rheumatic fever bares his name (Sydenham chorea, also known as St. Vitus' dance.)
Huntington's Disease (or Huntington's Chorea as it is also known) was both concisely and succinctly described as a specific disease entity in 1872 by George Huntington, an American physician. Huntington's Disease had been recognized as a disease entity before this point. Several reports before 1872 describe movement disorders that later authors attribute to Huntington's disease. These reports include letters, medical reports from physicians, and even a now-lost PhD thesis (see ref #3) However, the disease now bares Huntington's name in large part because of the clarity with which he presented the distinguishing features and identified the hereditary nature of the disease in his brief paper. While chorea movement disorders had been well documented, Huntington believed that the distinguishing features of this disorder, namely the late onset and hereditary nature, set it apart from previously-described chorea. Ironically, because he had no evidence of the disease beyond the Long Island families in which he encountered it, he suggested in his report that it might be confined solely to these families, and therefore might be considered "merely as a medical curiosity."
Dr. Huntington's Background
George Huntington came from a long line of physicians and both his father and grandfather practiced medicine on Long Island, New York. As a boy, Huntington often accompanied his father on medical rounds and witnessed with an indelible horror the destruction of "that disorder" (as it was referred to in the families that it struck.) In addition to his own observations, Huntington was able to draw from almost eighty years worth of observations made by his father and grandfather of patients with chorea and their families on Long Island. These factors contributed to Huntington being able to produce his seminal paper at the age of twenty two, about a year after completing his medical degree at Columbia University in New York City. Unlike many other seminal papers (see, for instance, the feature article on the history Alzheimer's Disease), Huntington's paper gained quick attention from the medical and scientific communities.
More Information:
Links to Huntington's Disease Resources
Bibliography:
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Thomas H. Huxley |
http://neuroscience.about.com/library/weekly/aa070698HuntHist.htm
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