Huntington’s disease (HD) is an inherited progressive disorder of the brain that leads to uncontrolled movements, emotional instability, and loss of intellectual faculties.
HD results from degeneration of brain cells. Specifically affected early in the disease are cells of the basal ganglia, a structure deep in the center of the brain where movement is coordinated. Later, cells of the brain’s outer surface - or cortex, which control the functions of thought, perception, and memory - are attacked.
Today, HD directly affects a total of about 25,000 people in the U.S., and at least 100,000 of their blood relatives live with constant uncertainty as they look for signs indicating that they, too, may have inherited the gene that will cause progressive disability and eventual death.
The prevalence rate is probably understated because of misdiagnosis, and the number of deaths caused by HD is likely to be under-reported.
HD is inherited in an autosomal dominant manner. The gene responsible for the disease has been located on chromosome number 4.
An affected parent can pass HD along to his or her offspring, and each child has a 50 percent chance of inheriting the HD gene and developing the disease.
HD occurs throughout the world in all ethnic groups. Clinical onset is usually between 30 and 50 years of age.
The first signs of HD may be subtle - a tic here, a twitch there, unexplained fluctuations of mood, an awareness of becoming more clumsy, depressed, or irritable than usual. There is a slurring and slowing of speech. Diagnosis at this early stage, however, is particularly difficult, since symptoms may be indistinguishable from normal variations in mood and behavior or from changes induced by other causes.
The effects of the disease are grim. As the disease progresses, the brain-cell death that is the basis of symptoms continues. As symptoms worsen, patients develop slurred speech, writhing movements known as chorea, and later, dementia.
Eventually, HD patients have difficulty communicating and are confined to a wheelchair or bed. Death usually occurs 15 to 20 years after the first symptoms appear, and is often caused by factors indirectly related to the disease, such as choking, head traumas, or infection.
The medical history (including symptoms and family history) as well as the physical examination are important. Genetic testing permits presymptomatic detection and definitive diagnosis of the disease.
There is at present no known means of altering the disease process or the fatal outcome. The choreic movements can be controlled by the use of neuroleptic agents, including dopamine receptor blockers such as haloperidol and perphenazine, and presynaptic dopamine depletors such as reserpine. Behavioral disturbances may respond to clozapine.
Using these drugs combined with supervision of the patient’s daily activities allows for management at home during the early stages of the disorder.
What tests need to be done to diagnose Huntington’s or to rule out any other cause?
What type of treatment do you recommend?
Will you be prescribing any medications? What are the side effects?
How rapid does this disease progress? And what should be expected?
If a test shows the presence of a gene before any symptoms are present, does this definitely indicate the disease will develop?
Should a genetics counselor be consulted?
Genetic testing for HD remains a personal decision which should be considered very carefully. Although the test may now be technically less complex, the personal implications remain the same and are substantial.
Anyone seeking genetic testing should do so only through programs in which protocols for testing have been submitted to the Huntington’s Disease Society of America, and which are known to have reputable pre-test and post-test counseling programs.