Huntington Disease (HD) is an autosomal dominant disorder of the CNS, characterised by involuntary movements, impaired motor co-ordination and dementia. HD is caused by dynamic mutations of the (CAG)n tract in exon 1 of the Huntingtin gene (HTT) on chromosome 4p.16.3. Abnormally expanded CAG repeats in this region is thought to acquire a novel deleterious function which results in neuronal dysfunction and neurodegeneration. Age of onset is inversely correlated with number of CAG repeats.
Diagnostic tests are ONLY accepted from Neurologists, Psychiatrists or Clinical Geneticists referring patients with definite motor signs of HD. A signed consent form is required (forms are available from www.mangen.org.uk). Pre-symptomatic testing is only offered in the context of the internationally agreed counselling protocol, and predictive test samples can ONLY from be accepted from Clinical Geneticists. Requests for prenatal diagnosis requests should also be referred through the Clinical Genetics Service.
Price & reporting times
NHS referrals to this service are paid for where there is an existing specialist commissioning contract for genetic testing. In other cases please contact the lab for prices.
|Test||NHS Price (£ )||Non NHS Price (£)||TRT|
|Mutation diagnostic test||POA||POA||28 cd|
|Prenatal diagnosis||POA||POA||3 cd|
Test validation & quality assurance - information for users
On testing for CAG repeat size most individuals fall clearly into the normal range or the expanded range consistent with HD neuropathy. Less than 1% of tested individuals fall into an intermediate category and are reported as such.
Pre-natal: amniotic fluid (minimum 15ml)/chorionic villus biopsy (CVB) (minimum 10mg) sample plus 4ml EDTA maternal blood sample
Post-natal: 2 x 4ml EDTA blood samples (please note: any post-natal test requests must be accompanied by a HD consent form)
Please see our referral guidelines for more information.
OMIM Number(s) - 143100
Gene(s) - Huntingtin (HTT)