Huntington's disease (HD) was described by George Huntington (1850-1916) who was born in Long Island, New York. He described this disorder in his only known written article called 'on chorea'. Huntington's disease is a genetic disorder (inherited due to a faulty gene) which usually affects people in their 40s and 50s. It primarily affects the brain, with a gradual loss of control of movement, memory and mental ability. HD is also associated with personality changes and depression as well as other mental illnesses. There is currently no cure for HD, although many strategies may be used to improve the quality of life for sufferers and their carers.

HD affects a wide range of brain activities and symptoms gradually become apparent in middle age. Changes in personality or mood may be the earliest signs of the disease, followed by problems with memory and abnormal uncontrollable movements. Personality change may occur as much as 10 years before abnormal movements are noticed. Most symptoms become progressively worse, although some people have fewer involuntary movements later in the course of the disease. Death usually occurs 15-20 years after the first symptoms, as a result of a general decline in health, or of more specific causes such as difficulty swallowing which leads to choking on food.

Movement disorders

The abnormal movements, which gave HD its former name of Huntington's chorea (chorea is a Greek word meaning dance), are typically rapid, jerking movements over which the person has no control. These movements can involve all four limbs and the trunk and specific movements of the face and head can also occur. Other abnormal movements that may develop throughout the course of the disease include slower, writhing movements of the arms and legs (known as athetosis), strange postures due to muscle spasm (dystonia) and slowing of voluntary movements in a manner similar to Parkinson's disease. Sudden jerking movements of the limbs or trunk, known as myoclonus may occur. HD Patients may also find themselves more unstable and prone to falls when standing. Chorea may involve speech function and walking which has a peculiar 'lurching' appearance. This can lead to unsteadiness and falls.

Eye movement

Rapid movements of the eyes are also affected, particularly on looking up and down. People with Huntington's disease can have difficulty in looking sideways too and may have to move their head to achieve full lateral vision. This is known as oculomotor apraxia.

Parkinsonism

'Parkinsonism' means the features of Parkinson's disease but due to other conditions. Many patients develop signs suggestive of parkinsonism with slowness of movement and increased muscle tone (rigidity). This usually occurs later in the disease. In juvenile-onset HD, and rarely in older patients, the condition may present with parkinsonism rather than chorea.

Memory and other neurological symptoms

Affected persons experience forgetfulness, which gradually worsens throughout the illness. They may also find difficulty with concentration, planning, and carrying out tasks that involve sequences of events. Thinking and thought processes appear to be slower in general but the ability to talk and understand language is preserved even in the later stages of the illness. People may also experience sensory symptoms such as numbness or pain.

Psychiatric symptoms

Many factors contribute to the psychiatric problems faced by patients with HD; stress and concern about the nature of the condition, family relationships and social support as well as the disease process in the brain itself.

Depression is a major problem in HD, affecting up to half of all sufferers. This may appear before other symptoms and may also occur in non-HD members of the family as knowing the disease affects someone in the family is a significant strain for them. Common 'biological' symptoms of depression include difficulty sleeping, and loss of appetite and weight.

Personality change also occurs early in the illness, and can appear as a lack of will and interest in life or as increased anger and irritability. This may be closely followed by changes in behaviour such as impulsive actions or violence, placing additional strain on the patient and the family. Disinhibition may cause the HD sufferer to respond unexpectedly to social situations. Antisocial personality disorder may also occur. Schizophrenia is also more common in HD than in the general population (5-10 per cent versus 1 per cent). Patients may complain of hearing or feeling things, or other hallucinations, and may develop unusual or paranoid beliefs.

HD may also be associated with alcoholism and sexual promiscuity. Suicide is also more common in HD. Another condition known as 'intermittent explosive disorder', which includes irritability, can occur.