What is it?
Huntington’s disease is a genetic and hereditary neurodegenerative disease. By destroying neurons in certain areas of the brain, it causes serious motor and psychiatric disorders and can lead to a total loss of autonomy and death. The gene whose alteration causes the disease was identified in the 1990s, but Huntington’s disease remains incurable to this day. It affects one in 10,000 people in France, which represents about 6,000 patients.
Symptoms of Huntington’s disease
It is sometimes still called “Huntington’s chorea” because the most characteristic symptom of the disease is the involuntary (so-called choreic) movements it causes. However, some patients do not have choreic disorders and the symptoms of the disease are broader: to these psychomotor disorders are often added psychiatric and behavioral disorders. These psychiatric disorders that occur frequently at the beginning of the illness (and sometimes occur before motor disorders) can lead to dementia and suicide. Symptoms usually appear around 40-50 years, but early and late forms of the disease are observed. Note that all carriers of the mutated gene declare the disease one day.
The origins of the disease
The American doctor George Huntington described Huntington’s disease in 1872, but it was not until 1993 that the causative gene was identified. It was located on the short arm of chromosome 4 and named IT15. The disease is caused by the mutation of this gene that drives the production of huntingtin protein. The precise function of this protein is still unknown, but we know that the genetic mutation makes it toxic: it causes deposits in the middle of the brain, more precisely in the nucleus of the neurons of the caudate nucleus, then of the cerebral cortex. However, it should be emphasized that Huntington’s disease is not systematically related to IT15 and may be caused by mutation of other genes.
Risk factors for Huntington’s disease
Huntington’s disease can be transmitted from generation to generation (it is called “autosomal dominant”) and the risk of transmission to offspring is one in two.
Prevention and treatment of Huntington’s disease
Genetic testing of the disease in people at risk (with a family history) is possible, but much framed by the medical profession, because the result of the test is not without psychological consequences.
A prenatal diagnosis is also feasible, but it is strictly regulated by law, because it raises questions of bioethics. However, a mother who is considering an abortion in the event that her fetus carries the altered gene has the right to request this prenatal diagnosis.
To date, there is no curative treatment and only the treatment of symptoms can relieve the sick person and slow down its physical and psychological deterioration: psychotropic drugs to alleviate psychiatric disorders and episodes of depression that are often associated with the disease ; neuroleptic drugs to reduce choreic movements; rehabilitation by physiotherapy and speech therapy.
The search for future therapies is moving towards the transplantation of fetal neurons in order to stabilize the motor functions of the brain. In 2008, researchers from the Institut Pasteur and the CNRS proved the brain’s ability to repair it by identifying a new source of neuron production. This discovery raises new hopes for the treatment of Huntington’s disease and other neurodegenerative diseases, such as Parkinson’s disease.
Gene therapy trials are also underway in several countries and are moving in several directions, one of which is to block expression of the mutated huntingtin gene.