Huntington Disease

Genetic, autosomal dominant — mutant gene on the short arm of chromosome 4 (one genetic mutation accounts for the vast majority of cases). Each child of an affected parent has a 50% risk.

Murtagh’s triad: chorea + abnormal behaviour + dementia + family history.

Presentation

Onset of symptoms age 35–50; progressive over time; death 15–20 years after diagnosis. Starts with chorea and motor symptoms — flicking arm movements, facial grimacing, lilting gait, ataxia, dystonia — followed by progressive intellectual deterioration/dementia, impulsiveness, and sometimes psychotic symptoms with delusions.

Investigations

Genetic testing confirms the diagnosis — refer the family to a clinical geneticist.

Management

Refer to neurology if suspected; more advanced disease needs neuropsychiatry input. VMAT2 inhibitors (tetrabenazine, or the better-tolerated once/twice-daily deutetrabenazine) are established symptomatic treatments for chorea. Gene-silencing (antisense oligonucleotide) disease-modifying therapies have been trialled but have so far failed to show benefit. There is no disease-modifying cure — treatment is otherwise supportive.