Causes of Huntington's Disease

Why do one in 10,000 people get Huntington's disease? While the exact Huntington's disease causes are not fully understood, it is known that Huntington's disease is hereditary.

There are approximately 30,000 known cases of Huntington's disease in the United States. That means about 150,000 Americans have the potential to inherit Huntington's disease from a parent. Here you'll find an overview of what is known about Huntington's disease causes, and how it is inherited through generations.

Huntington's disease is a dominant inherited disease. That means that a person only needs to inherit one copy of a mutated gene to get HD. Therefore, people who have Huntington's disease have a fifty percent chance of passing Huntington's disease on to their children.

 

Huntington's stems from an inherited gene that is just slightly larger than normal. This gene has been named the huntingtin gene. This gene is the result of an abnormal expansion of a repeated section in the DNA sequence of the gene. The affected section in the sequence is the area that encodes the amino acid glutamine.

 

A normal, healthy person has a string of between 9 and 39 glutamines. Because of the abnormal expansion of the huntingtin gene, Huntington's patients have between 36 and 121 glutamines. The large size of this section makes the huntingtin protein more unstable, which in turn creates an abnormal shape. How can this abnormal shape cause the uncontrolled movements, emotional disturbances and mental deterioration classic of Huntington's?

Huntington's disease causes neuron death in three parts of the brain: the striatum, the substantia nigra and the thalamus. While the mutated gene coding is certainly the cause, exactly how the mutation results in the death of nerve cells is not fully understood.

 

Research has shown that the abnormal huntingtin protein may interact with a large number of other proteins, and can perhaps interfere with their normal functioning. Research has also indicated that the mutated huntingtin protein forms clumps inside the neurons of people with Huntington's disease. Whether these clumps actually cause the death of nerve cells is uncertain. These clumps may simply be a by product of the mutated protein.

 

Mayo Clinic. (2003, August 14). Huntington's disease [DS00401].