Huntington disease is an autosomal dominant inherited disease with its onset occurring most often in adult life i.e. its symptoms begin at age 30 to 40 years. Death usually occurs after 15 to 20 years after onset of this disease.
The cause of this disease has been traced to a single gene defect on chromosome 4. This gene contains a protein huntingtin, the function of this protein is still unknown and how this protein causes the disease is also unknown. The codon CAG that encodes glutamine is repeated many times than normal. Huntington disease affects men and women with equal frequency and unfortunately reveals itself only after they have had their children.
Signs and Symptoms
Patients of this disease show following signs and symptoms.
Choreiform Movements: These are flicking and involuntary movements in individual muscles of extremities as well as there is twitching of the face and facial grimacing is present. In the late case, more muscle groups get involved, which make the patient immobile and unable to speak or swallow.
Reason: These abnormal movements in this disease is believed to be caused by loss of cell bodies of the gamma amino butyric acid (GABA) secreting neurons present in the caudate nucleus and putamen along with acetylcholine-secreting neurons in many parts of the brain. The terminals of the axons of the GABA neurons normally inhibit portions of the globus pallidus and substania nigra. As a result of this loss of inhibition, the spontaneous outburst of globus pallidus and substania nigra activity occur and this results in distortional movements.
Progressive Dementia: This occurs with the loss of memory and intellectual capacity on an individual with this disease. This dementia is not result from the loss of GABA neurons but from the loss of acetylcholine secreting neurons especially in the thinking areas of the cerebral cortex.
In children this disease show rapid progression, chorea and the rigidity are the dominant symptoms. There are complaints of anxiety and depression along with aggression and irritability with this disease.
It is made on the basis of history and physical examination. On CT scan, there are enlarged lateral ventricles seen which are due to degeneration of the caudate nuclei. Now a days genetic testing can be done on an embryo to confirm this disease. MRI and PET are also considered best in determining the brain changes which can give the results before the symptoms of the disease arise.
Although there is no perfect medical cure of this disease but with the help of certain medicines, many symptoms can be treated to some extent. For example by the use of antipsychotics or neuroleptics, tetrabenzanine and benzodiazepines a relief from chorea can be achieved. Anti depressant are also found useful in these patients. They can provide them with calm mind and remove depression and anxiety. They also enhance their good mood. These drugs result in increase levels of serotonin and norepinehphrine in the brain which are essential for normal moods. The rehabilitation has not seen so successful but it can give little improvement in these patients’ walk and speech.