Genetics of Huntington’s disease and special considerations for pre-symptomatic genetic testing

Huntington’s disease is a fatal and progressive neurodegenerative disease characterised by a shrinkage of the brain, movement abnormalities and cognitive decline. It is an autosomal dominant disease caused by a DNA mutation in the huntingtin gene located on chromosome 4. Children with one parent affected by Huntington’s disease have a 50% risk of inheriting the faulty gene. Genetic testing for Huntington’s disease has been available for more than 20 years and can be used for pre-symptomatic or confirmatory testing. Healthcare professionals across a variety of specialties and settings, including primary care, may encounter patients who ask to be genetically tested for Huntington’s disease.This article explains the genetics of Huntington’s disease, describes its clinical diagnosis, identifies some of the implications of pre-symptomatic genetic testing and discusses situations that require special consideration before the decision to conduct genetic testing is made. The article is written from a US perspective, but the implications and challenges discussed are highly relevant in the UK.