Huntington’s disease is a devastating inherited neurodegenerative disease characterised by progressive motor, cognitive, and psychiatric symptoms. Patients may present with any of these symptoms, and familiarity with the phenotype is therefore important. Chorea and loss of balance are early symptoms that patients notice, although families often notice cognitive or personality changes before this.

The disease occurs in all racial groups but is most common in people of northern European origin. Its prevalence in the Western hemisphere is 7-10/100 000.^w1 The mean age of onset of symptoms is 40 years, but juvenile onset (<20 years) and older onset (>70 years) forms are well recognised. The Huntington’s Disease Association (HDA) has records of 6161 adults with symptomatic Huntington’s disease and 541 children with juvenile Huntington’s disease (in England and Wales) at the time of writing. This is a conservative estimate of prevalence because it includes only those people in contact with the HDA, and it suggests that the true prevalence of the disease is higher than previously thought.1

Although relatively uncommon, Huntington’s disease can be devastating for patients and their families. People who are at risk of developing the disease because of a family history face difficult decisions about genetic testing. We review …