What is chorea?

Choreic movements are involuntary movements, often sudden, anarchic, non-stereotyped and unpredictable, which can affect all the muscles of the body. They are a symptom whose causes may be genetic (Huntington’s disease or chorea, for example) or acquired: thyroid disorders, drug causes, etc.

Huntington’s chorea: a rare genetic disease

A hereditary neurodegenerative disease, Huntington’s chorea (or Huntington’s disease) is a rare disease caused by a mutation in an HD gene (coding for a protein called huntingtin). The genetic mutation was identified in the 1990s. This rare disease affects the central nervous system and affects 18,000 people in Europe, i.e. 5 cases per 100,000 people. Men and women are affected with equal frequency. “It is an autosomal dominant disease, that is to say that a person affected by this disease has a 50% risk of transmitting the disease to their child and 50% of not transmitting it.underlines Pr Christine Tranchant, neurologist at the University Hospital of Strasbourg.

In so-called autosomal dominant diseases, it is enough for one copy of the gene out of the two that we have (one inherited from the father, the other inherited from the mother), to be pathological to develop the disease. In this context, genetic counseling is essential for all family members who are at risk of carrying an HD gene mutation, even before the onset of symptoms. “It is very important to explain the mode of transmission and to communicate with the different members of the family to explain to them their risk of developing the disease”, continues the neurologist. A pre-symptomatic diagnosis can thus be considered in some adults.

It is possible to be a carrier of the HD gene mutation and still have children knowing that they will not be carriers of the genetic abnormality. “This is possible through prenatal diagnosis or through preimplantation diagnosis.” continues the specialist.

Huntington’s chorea: three groups of symptoms

This disease brings together different types of symptoms that can appear in random order and vary in their intensity depending on the individual expression of the patient.

Motor, cognitive and psychiatric disorders

Huntington’s disease is manifested in particular by motor symptoms. These are involuntary movements most often choreic. “Initially, these movements are not necessarily bothersome. Those around you notice that the person is constantly moving a part of the body. This can simply be interpreted as nervousness at the very beginning”, explains Professor Christine Tranchant. However, over time, these involuntary movements will gradually interfere with voluntary movements and become a source of clumsiness, walking, balance, speech and swallowing disorders until inducing a loss of autonomy. increasingly noticeable. In some cases, we can observe rather a muscular rigidity or a certain slowness of the movements.

Cognitive disorders characterized by difficulties of organization, abstraction, attention and concentration, even, secondarily, of memorization, can reveal the disease or appear during its evolution. Frequently there is great apathy. “It becomes difficult to do several things at the same time and to plan actions. These symptoms will also lead to a loss of autonomy.explains the neurologist.

Psychiatric disorders also occur during the evolution of Huntington’s chorea: depression, behavioral disorders, anxiety and even psychotic states, especially in young patients.

Finally, Huntington’s disease can also be associated with weight loss (despite unchanged calorie intake), sleep disorders or circadian rhythm.

It is important to remember that even if a subject is a carrier of the genetic anomaly, he is only considered to have the disease when he develops the first clinical signs. Evolving from the appearance of the first symptoms, the disease worsens over fifteen or even twenty years. The first signs can appear in young people, in their twenties, or appear much later, at 60, 70 or even 80 years old. “All the symptoms do not settle at the same time, nor with the same intensity. The evolution profile will be different from one person to another, including within the same family.details the specialist.

Diagnosis of the disease is established through genetic study (testing of the HD gene by a blood test) in dedicated centres. “The mutation corresponds to the presence of an abnormally increased number of triplets of the CAG nucleotide sequence in the HD gene”explains the specialist.

Multidisciplinary care

The management of Huntington’s disease is based on treatments aimed at relieving symptoms and improving the quality of life of patients. For motor symptoms, neuroleptic treatments and anti-psychotics are usually prescribed. Physiotherapy and speech therapy are also recommended. “There is currently no treatment to slow down the progression of this disease, but therapeutic trials are regularly offered. summarizes the neurologist.

The medical follow-up of these patients involves several specialists: general practitioner, neurologist, psychiatrist, physiotherapist, speech therapist… At an advanced stage of the disease, social support is also established (professional reclassification, request for social aid in connection with the loss of autonomy, etc.).

Sydenham’s chorea and other forms of chorea

Consecutive to a streptococcal infection not treated with an antibiotic, Sydenham’s chorea (found under the term “Saint Vitus dance” is also manifested by choreic movements. “A production of antibodies supposed to protect against streptococcus will, by an autoimmune mechanism, reach the central nervous system., explains Professor Christine Tranchant. The arrival of antibiotics has gradually made this form of chorea disappear.

Other forms of chorea may be caused by metabolic disorders (hypo or hyperglycemia), thyroid dysfunction, or other rarer genetic diseases than Huntington’s disease. In addition, taking certain medications can also cause chorea. Finally, paraneoplastic chorea is observed in the presence of cancer.

The medical management of these particular choreas can be symptomatic or relate to the treatment of the cause.