Background

Huntington disease (HD) is an autosomal dominant neurodegenerative disease caused by a cytosine–adenine– guanine (CAG) expansion in the huntingtin gene (HTT) that codes for an abnormal polyglutamine tract. In carriers of the HD mutation, the disease manifests as an adult-onset disease but is preceded by an asymptomatic stage when cellular dysfunction and progressive neurodegeneration are already occurring in the brain. Therapeutic approaches targeting the cause of HD are currently in clinical development but may prove more effective if intervention is initiated prior to clinical onset. However, current methods of predicting age-of-onset are inaccurate (e.g. CAG repeat length in HTT has been correlated with age-of-onset yet it only accounts for 50–60% of the variability with other genetic and environmental factors