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Foundation Sciences · Genetics

Huntington Disease

⏱️ 30 mins read 📖 Genetics 🎯 MLA Relevance: High

Huntington disease is an autosomal dominant neurodegenerative disorder caused by CAG repeat expansion in the HTT gene, presenting in mid-adulthood with chorea, cognitive decline and psychiatric features.

📌 Learning Objectives

  • Describe the underlying mechanism of Huntington Disease.
  • Identify the key clinical features and complications of Huntington Disease.
  • Outline the appropriate investigations and management of Huntington Disease.
  • Discuss the implications for patients and families of Huntington Disease.
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Curriculum Mapped
UK MLA Curriculum

📋 Overview

Onset typically age 30–50; full penetrance with ≥40 CAG repeats. Treatment is symptomatic (e.g. tetrabenazine for chorea).

🔬 Basic Science

Onset typically age 30–50; full penetrance with ≥40 CAG repeats. Treatment is symptomatic (e.g. tetrabenazine for chorea).

🏥 Clinical Relevance

Anticipation occurs particularly with paternal transmission.

🧪 Investigations

Investigation depends on clinical context: relevant blood tests, imaging, and specific genetic or histopathological tests as appropriate. Refer to specialist services where indicated.

💊 Management

Management is condition-specific and typically multidisciplinary, combining medical therapy, surgical intervention where appropriate, supportive care, and family/genetic counselling.

Revision Resources – expand the sections below for high-yield notes, exam pearls, key facts and further reading.

🎯 MLA High-Yield Notes & Quick Revision ⌄
Common SBA themes: recognising the underlying mechanism, identifying classic clinical features, and choosing the first-line investigation or management step. Watch for inheritance pattern and characteristic associations.
huntington cag repeat htt chorea anticipation
  • Huntington disease is autosomal dominant due to CAG repeat expansion in HTT.
  • ≥40 CAG repeats produce fully penetrant disease.
  • Onset usually between 30 and 50 years.
  • Triad: chorea, cognitive decline and psychiatric features.
  • Predictive testing follows a structured counselling protocol.
⭐ Exam Pearls ⌄
⭐ High Yield
Huntington disease is autosomal dominant due to CAG repeat expansion in HTT.
≥40 CAG repeats produce fully penetrant disease.
Onset usually between 30 and 50 years.
Triad: chorea, cognitive decline and psychiatric features.
Predictive testing follows a structured counselling protocol.
💡 Clinical Pearl
Huntington: Anticipation occurs particularly with paternal transmission.
⚠️ Exam Tip — Common Mistakes
Confusing the mechanism of Huntington Disease with related conditions.
Missing classic clinical features of Huntington Disease in SBA stems.
Failing to consider Huntington Disease in the differential diagnosis.
🔑 Key Facts ⌄
Huntington disease is autosomal dominant due to CAG repeat expansion in HTT.
≥40 CAG repeats produce fully penetrant disease.
Onset usually between 30 and 50 years.
Triad: chorea, cognitive decline and psychiatric features.
Predictive testing follows a structured counselling protocol.
🔗 Related Topics ⌄
🔬 Trinucleotide Repeat Disorders Foundation Sciences → 🔬 Autosomal Dominant Disorders Foundation Sciences → 📚 Movement Disorders
📚 References ⌄
  1. GMC MLA Content Map
  2. NICE Clinical Knowledge Summaries
  3. BMJ Best Practice

Further Resources

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