Huntington’s Disease: Causes, Symptoms, and Research Advances

What Is Huntington’s Disease?

Huntington’s disease can be devastating. The illness reduces your ability to control your body’s movements and can also give rise to problems with thinking and memory. It’s caused by changes in one gene, and those changes are passed down from generation to generation. Symptoms worsen over time, and the disease is eventually fatal.

Genetic Cause

The disease is caused by a gene that makes a protein called huntingtin. Certain DNA repeat expansions in the huntingtin gene lead to a defective protein that has toxic effects in brain cells, causing them to die—especially in the areas that control voluntary movements.

Symptoms and Progression

  • Chorea: Uncontrollable, irregular movements.
  • Akinesia: Body stiffness and trouble moving.
  • Swallowing and eating difficulties.
  • Cognitive decline and memory problems.
  • Emotional disturbances, including hallucinations and delusions.
  • Impaired posture, speech difficulties, and eventual loss of ability to walk or care for oneself.

Inheritance and Genetic Testing

Each person inherits two copies of the huntingtin gene—one from each parent. A single copy with too many CAG repeats is sufficient to cause the disease.

Repeat ranges:

  • Fewer than 27 repeats: Normal, not associated with disease.
  • 27–35 repeats: Not likely to develop the disease but may pass an expanded gene to offspring.
  • 36 or more repeats: Associated with Huntington’s disease; higher repeat counts lead to earlier onset, which in rare cases can occur in childhood.

A genetic test can determine the number of repeats in your huntingtin genes, but a formal diagnosis requires a clinical exam and characteristic movement symptoms.

Current Research and Future Therapies

Scientists are studying ways to lessen the effects of the defective huntingtin gene, including:

  • Altering the gene or lowering levels of the defective protein.
  • Investigating other genes that influence repeat expansion and toxicity.
  • Using animal models that mimic human repeat expansion to test interventions.
  • Screening for molecules that can turn off genes involved in repeat expansion.

Managing Symptoms

While there is no therapy to prevent or stop the disease, treatments can improve quality of life by:

  • Decreasing uncontrolled movements.
  • Reducing hallucinations and delusions.
  • Alleviating emotional symptoms.

Identifying the disease early may make these treatments more effective.

Reference

Distinct mismatch-repair complex genes set neuronal CAG-repeat expansion rate to drive selective pathogenesis in HD mice. Wang N, Zhang S, Langfelder P, Ramanathan L, Gao F, Plascencia M, Vaca R, Gu X, Deng L, Dionisio LE, Vu H, Maciejewski E, Ernst J, Prasad BC, Vogt TF, Horvath S, Aaronson JS, Rosinski J, Yang XW. Cell. 2025 Mar 20;188(6):1524-1544.e22. doi:10.1016/j.cell.2025.01.031. PMID: 39938516.

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