Huntington’s Disease (HD) is a rare, hereditary neurodegenerative condition. Symptoms include movement, mood and cognitive disturbances, which in the majority of cases appear in a persons mid-adult life - between 30 and 50 years of age. Approximately 5-10% of people have symptom onset before the age of 20 (Juvenile HD) and 10% have onset after age 60. The symptoms of HD may vary in severity, age of onset and rate of progression from individual to individual and between members of the same family. There are currently no therapies that effectively treat the underlying causes of HD, however there are treatments that can alleviate some symptoms and improve quality of life for those living with HD.
The exact time of HD symptom onset is usually difficult to determine. Some individuals may have very obvious movement changes, but relatively mild behavioural symptoms and cognitive impairment initially, while others may experience significant emotional changes or cognitive difficulties for many years before showing any changes to motor function. HD is characterised by a combination of motor, cognitive and emotional symptoms.
Motor symptoms - Changes in function affect posture, balance and gait. Speech and swallowing difficulties and weight loss are also common. Early referrals to rehabilitative therapies including physiotherapy, speech and language, occupational therapy and dietetics help to maintain function.
Emotional symptoms - Changes commonly include anxiety, apathy, depression, irritability, impulsiveness, sleep disturbance and social withdrawal. More rarely, mania and delusional thoughts can occur. Individuals may also experience suicidal thoughts, especially in the early stages of HD. Most people with HD and their families perceive the behavioural symptoms to be more distressing than other symptoms. Psychological and psychiatric supports are important in managing emotional changes.
Cognitive symptoms - HD is characterised by the gradual impairment of comprehension, reasoning and judgement. Symptoms include slower thinking , reduced self-awareness and difficulties organising, planning, making decisions and problem solving. Maintaining routines, reducing distractions and using prompts and good communication strategies can help to reduce the impact of cognitive impairments.
HD is caused by an expansion in the IT-15, or huntingtin gene, on chromosome 4. Each child of a parent with the HD gene has a 50% chance of developing HD.
A diagnostic test is used to confirm the diagnosis of HD in a person showing symptoms of the disease. The test is carried out to confirm a clinical likelihood that a person already has HD.
A predictive test for HD is available to a healthy person over 18 years, who has no symptoms, but who has a family history of HD. Not everyone at risk of HD wishes to pursue a predictive genetic HD test, and having the test remains an individual choice.
Genetic counselling and information on pre-symptomatic genetic testing is available from the Genetic Centre - Tel: (01) 409 6739, Website: www.genetics.ie
Treatment and Care
There are currently no therapies to effectively treat the underlying causes of HD but symptoms can be managed with timely multidisciplinary support including: neurology, genetic services, neuropsychiatry, neuropsychology, neuro-rehabilitative therapies (physiotherapy, speech & language, dietetics, occupational therapy) and specialist care. Much can be done to improve the quality of life of a person with HD and their family members.
Maintaining a healthy body weight is essential because people who are under weight lose muscle mass and therefore feel weaker, become more apathetic or depressed and are more prone to catching infections. Exercise, social and psychological support can help manage a persons physical and mental well-being. Medication should be reviewed regularly to ensure it remains effective in treating symptoms over the course of the illness. For more information see the HD Handbooks on the Information page.
Standards of Care
The European Huntington’s Disease Network (EHDN) have formed a number of working groups to encourage new collaborative work in the care of HD with the aim of developing evidence based guidelines for best practice. The standard of Care working group comprises of clinicians and allied health professionals from various disciplines, from Europe and the USA. All contributed their wealth of expertise and knowledge gained through working with HD patients and their families. A special edition issue of the Journal of Neurodegenerative Disease Management focuses on Standards of Care for the clinical management of HD. Please follow the link for open access to this series of articles which is kindly supported by CHDI Foundation: A standard of care for Huntington’s disease.
Prevalence of HD
Professor Patrick Morrison conducted a survey in Northern Ireland in 2001 which estimated the prevalence of 10-16 people per 100,000 (Lancet Neurology). His analysis of more recent data suggests a prevalence of 14-16 per 100,000. Based on the Republic of Ireland population of 4,670,976 (July 2011) this would indicate approximately 700 people with HD and a further 3000 at risk.
How does the disease get its name?
The disease is named after Dr. George Huntington, an American physician, who was the first to publish a precise description of the symptoms and course of the disease in an article written in 1872.