Huntington’s Disease — Discovery and Treatment
Huntington’s Disease (HD) is a rare, progressive neurodegenerative disorder which can manifest its effects in adulthood. First described by George Huntington among East Hampton residents in 1872, it wasn’t until 1983 when the Huntingtin (HTT) gene was molecularly mapped to a human chromosome. It was further understood that a section of the HTT gene contained several repeated triplet nucleotides — CAG — and the number of repeats within this gene determined an individual’s risk level for developing HD. People with 6 to 35 CAG repeats are not affected, those with 36–39 are at greater risk, and if 40 or more CAG repeats are present then symptoms of the disease will occur. Located on one of the 23 chromosomes that hold genetic information, HD is caused by a single flawed gene found on chromosome 4.
A precise risk assessment for Huntington’s disease can be determined via molecular genetics, yet unfortunately, there is no cure or successful treatment to reverse the condition. However, there are several medical and lifestyle approaches available to help manage symptoms and improve quality of life. Research is ongoing in attempts to identify more effective management solutions. To understand the cause of this affliction, scientists have examined the concept of a defective huntingtin protein, where the gene codes for this protein are identified as the source of HD. While scientists continue their research into the normal function of huntingtin, it has been determined that a defective version causes abnormal movements, progressive decline in cognitive skills, and mental health issues such as depression and irritability.
Involuntary movements of the limbs typically characterize HD and upper body, along with memory loss, concentration problems, poor judgment and planning skills, reduced reasoning capacity, and changes in mood, particularly depression, anxiety, and irritability. It can manifest as early as age two or as late as eighty and can also cause an individual to exhibit obsessive-compulsive behavior such as asking the same questions or performing the same activities multiple times.
The following treatments have been recommended by international experts as first-line strategies for three of HD’s most troubling symptoms:
· Tetrabenazine, a drug recently approved by the Food and Drug Administration (FDA) for Huntington’s, is another medication used by some healthcare providers.
· For less severe, nonthreatening irritability, it is recommended to try selective serotonin reuptake inhibitors (SSRIs), an antidepressant.
· SSRIs are recommended by experts as a standard treatment for obsessive-compulsive thoughts and behaviors.
Generally accepted guidelines should also be followed for anxiety, depression, and insomnia in addition to treating Huntington’s symptoms. It is important for people with Huntington’s to keep all their medical appointments and not get discouraged when it takes a while to find the right medications and dosages.
New drugs being delivered directly to the brain and gene therapy and other approaches based on the underlying genetic defect may alleviate some of the symptoms of HD.
As well as studying the development and progression of Huntington’s disease, researchers are also studying lifestyle choices and environmental factors. Researchers study diet, exercise, and stress to determine how to improve the quality of life of people with Huntington’s disease and their families. The goal of Huntington’s disease research is to develop effective treatments and ultimately find a cure.
Research is also focusing on how a few extra sequences in huntingtin protein cause Huntington’s symptoms and the normal function of the protein. If successful, this may lead to a greater understanding of an array of other brain pathologies, such as Alzheimer’s, Parkinson’s, and amyotrophic lateral sclerosis (ALS).
Written By: Lawrence D. Jones, Ph.D.
