Clinical features: An inherited disorder of the central nervous system, early symptoms are subtle and include clumsiness, lack of concentration, short-term memory lapses, depression and mood swings. The condition is progressive and later in the illness affected people may experience involuntary movements (chorea), weight loss, difficulty in speech and swallowing and continuing emotional and psychiatric disturbances. Although there is currently no cure for Huntington disease, treatment is available to alleviate some of the symptoms. In the final stages of the illness full nursing care will be needed. The mean age of onset of symptoms is 35 to 44 years and the median survival time is 15 to 18 years after onset. 25% of gene carriers develop first symptoms and signs after the age of 50 years. Between 7 and 10% of individuals with HD have an onset before 20 years of age (This is called juvenile HD see below). HD shows full penetrance.
Incidence: In Western Europe the prevalence of Huntington disease is about 5 per 100,000.
Inheritance : Autosomal dominant.
Gene: Huntington disease is caused by a mutation in the Huntington gene (HD) on chromosome 4. The mutation is an amplified, unstable CAG triplet (trinucleotide) repeat and the age of onset is inversely correlated with the CAG repeat length - the larger the number of repeats, the earlier the onset of the condition. In affected individuals there are more than 36 repeat copies. In individuals with adult-onset HD there are usually 40 ? 55 repeats, whereas those with the juvenile onset have 50 or more copies. The age of onset in the repeat range of 36 ? 39 is less certain. The CAG repeat number usually increases from one generation to the next (amplification); but the increase in the number of repeats is greater when a father passes on the 50 copies (Juvenile HD) have usually inherited the condition from their father.
Prenatal diagnosis: Yes. Please refer to your local clinical genetics service prior to a pregnancy. This ensures family members are offered appropriate advice and investigations, to confirm whether or not prenatal diagnosis is possible.
UK Support Group: Huntington's Disease Association Neurosupport Centre Norton Street Liverpool L3 8LR
Telephone: 01279 507656
Web: www.hda.org.uk
If you would like further information on Huntington disease please go to either:-
The Least You Need to Know Coffee Break Summary Pitfalls to Avoid Find Out More Clinical Scenarios at Genepool - Huntington disease
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