Huntington’s disease is considered one of the most common genetic brain disorders, affecting 300,000 Americans annually and placing another 200,000 at risk. The disease progresses slowly over a ten to twenty year period and eventually robs the affected individual of the ability to walk, talk and think. The disease usually manifests itself between the ages of 30 and 50. Both the basal ganglia, which control coordination, and the brain cortex, which serves as the center for thought, perception and memory are affected.

Symptoms

Involuntary jerking movements of the limbs, torso and facial muscles are the most recognizable symptoms. These are often accompanied by mood swings, depression, irritability, slurred speech and clumsiness. Other symptoms become common as the disease progresses. These include difficulty swallowing, unsteady gait, loss of balance, impaired reasoning and memory loss. Eventually, the affected person becomes totally dependent on others for care. Death is often the result of pneumonia, heart failure or another complication.

Diagnosis

A detailed clinical examination and family history are very important for an accurate diagnosis. Brain scans could also prove helpful. Genetic testing, which can be used to help confirm a diagnosis, has been simplified by the discovery of the gene that causes Huntington’s disease in 1993.

HD researchers and genetic counselors have developed specific protocols for predictive testing to ensure that the emotional and psychological consequences of a positive result are fully understood. This type of predictive testing is only available for adults, although children under 18 may be tested to confirm a diagnosis of juvenile-onset HD. Prenatal testing can be considered.

It is important to consider the ethical implications of testing, and to adequately inform the tested individual, as there is, at present, no cure or treatment for this condition.

Genetics and the Quest for a Cure

The HD mutation is an expanded triplet repeat in the HD gene. This abnormal gene codes for an abnormal protein called huntingtin. At present, the normal function of this protein is still unknown, but it is widely distributed in the brain and seems to be associated with proteins involved in transcription, protein turnover and energy production. The cause of HD, however, involves an new and toxic function.

Cell and transgenic animal models can replicate many features of the disease and are now being used to test new theories and therapies. Clinical and observational trials are being conducted. These could hopefully yield effective treatments that can delay the progression of the disease or delay the onset of the disease while researcher continue their quest for a cure.