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Huntington's disease and chorea
Huntington's disease is a dominantly inherited disorder (CAG repeat expansion in the HTT gene) combining chorea, psychiatric disturbance and cognitive decline — and in every new chorea you also search for reversible causes such as drugs, pregnancy, lupus and hyperglycaemia.
Why it matters in the exam
Questions present an adult aged 30 to 50 with involuntary "dancing" movements, irritability, depression and forgetfulness, whose father died of a similar illness; or a girl with chorea after a sore throat (Sydenham's chorea); or an older diabetic woman with one-sided movements (non-ketotic hyperglycaemia). They test inheritance (dominant, with anticipation mainly through paternal transmission), MRI (caudate atrophy), treatment of chorea (VMAT2 inhibitors such as tetrabenazine, with a risk of depression and suicidality), and the rules of predictive genetic testing (adults only, with counselling). A common distractor is testing an asymptomatic child at the parents' request. Remember the suicide risk in Huntington's patients and the need to support the family. The more repeats, the younger the onset, and in the childhood form rigidity and seizures dominate rather than chorea. The disease progresses over many years and no treatment slows it today; care is symptomatic and multidisciplinary, including physiotherapy, nutrition and psychiatric support.
Key points
- Huntington's: dominant, CAG repeats in HTT; 40 or more — full penetrance.
- Chorea, psychiatric disturbance and cognitive decline, with caudate atrophy.
- VMAT2 inhibitors reduce chorea but require monitoring for depression.
- Predictive testing only in adults and with genetic counselling.
- In every new chorea look for reversible causes: drugs, pregnancy, lupus, thyroid and glucose.
Summary table
| Cause | Clues | Treatment or step |
|---|---|---|
| Huntington's disease | Chorea, depression and irritability, executive decline; 40 or more CAG repeats — full penetrance | Tetrabenazine or deutetrabenazine (caution in depression), antipsychotics; genetic counselling |
| Sydenham's chorea | A child after streptococcal infection, part of rheumatic fever | Penicillin for secondary prevention; symptomatic treatment |
| Pregnancy and drugs | Chorea in pregnancy, the pill, levodopa, stimulants, antiseizure drugs | Stop the drug; usually resolves after delivery |
| Systemic and autoimmune | Lupus and antiphospholipid syndrome, hyperthyroidism, polycythaemia | Treat the underlying disease |
| Metabolic and structural | Non-ketotic hyperglycaemia (one-sided chorea, high putamen signal on T1), stroke in the subthalamic nucleus (hemiballismus) | Glucose control; usually improves |
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Sources
- International Guidelines for the Treatment of Huntington's Disease (Bachoud-Lévi et al., Frontiers in Neurology), 2019 — Chorea, psychiatric and cognitive symptoms
- HDSA Genetic Testing Protocol for Huntington's Disease, 2016 — Predictive testing and minors
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.