Huntington Disease

Huntington's disease is a progressive brain disorder that causes a breakdown of nerve cells in the brain. It is a genetic disease that causes physical, emotional, and cognitive problems.

Alternate Name

• Huntington chorea
• Huntington chronic progressive hereditary chorea

Associated Anatomy

Nerve cells in the brain

Epidemiology

About 3 to 7 per 100,000 people of European ancestry are likely to be affected by Huntington's disease. The disorder is less common in other populations of African, Chinese, and Japanese descent.

Symptoms of Huntington's Disease

• Personality and mood changes
• Depression
• Sudden weight loss
• Difficulty in speaking
• Unable to swallow food
• Loss of memory
• Involuntary body movements
• Loss of focus
• Abnormal eye movements
• A decline in cognitive abilities
• Hallucination
• Poor coordination
• Muscle rigidity
• Loss of decision-making abilities
• Difficulty in walking
• Uncontrollable twitching movements, called chorea
• Confusion
• Inability in understanding new information

Huntington's Disease Causes

Gene mutation

Mutation of a gene producing huntingtin, a protein, on chromosome number 4 results in Huntington's disease. Excess of huntingtin protein is toxic and damages certain brain cells.

The offspring (child) inherits the abnormal or defective gene from either of its parents leading to Huntington's disease in later stages of life.

Additional Type

Huntington's disease starts affecting the patient after the age of 30- 40 years. However, when it affects at a younger age, it is known as juvenile Huntington's disease. Juvenile Huntington's disease progresses faster than its adult onset. While adult Huntington's disease causes death after 10 to 30 years, juvenile Huntington's disease leads to death in 10 years.

Typical Tests Required for Huntington's Disease

The doctors diagnose Huntington's disease by inquiring about the patient's medical history, signs, symptoms, and physical examination, followed by some imaging tests.

Various diagnostic tests include

• Genetic testing - As Hungtington's disease is a genetic disorder, genetic testing is advised by doctors to confirm its presence.
• Brain function and imaging tests - Doctors may sometimes also recommend a CT scan or MRI scan to rule out other disorders.
• Neurological tests - to understand the effect of the disease on various neurological functions like reflexes, coordination, hearing, vision, etc.
• Psychiatric tests - to evaluate a patient's emotional state, coping skills, and behavioural patterns

Huntington's Disease Treatment

Huntington's disease can be managed using various treatment methods but is incurable.

Possible Treatment options are:

Medications

• Tetrabenazine and antipsychotic drugs for involuntary movements
• Diazepam for muscle rigidity and involuntary muscle contractions
• Antidepressants and mood-stabilizing drugs for depression and mood swings

Therapy

Different types of therapies that can help in slowing down the symptoms are

• Speech therapy
• Physical and occupational therapy
• Psychotherapy
• Physiotherapy

Risk Factors Associated with Huntington's Disease

• Family history of Huntington's disease

If either parents or grandparents have Huntington's disease, children are likely to inherit it.

Possible Complications of Huntington's Disease

Huntington's disease leads to physical, emotional, and cognitive inabilities. They lead to complications like:

• Suicides - frustration and depression increase suicidal tendency.
• Weaken immune system - sudden weight loss and difficulty swallowing food leads to immune deficiency, making the patient vulnerable to pneumonia and other infections.
• Fall injuries - poor coordination and involuntary movements lead to frequent falls and related injuries.

Huntington's Disease Prevention

• In-vitro fertilization

If any of the parents have a gene mutation or genetic history of having Huntington's disease, they can opt for in-vitro fertilization.

During in-vitro fertilization, the mother's egg is fertilized with the father's sperm in a laboratory. Then, the embryo is genetically tested and implanted in the mother's womb only if it does not have a gene mutation.

Expected Prognosis

When diagnosed with Huntington's disease, medications and other treatment options help manage the disease. They decrease the pace of symptom evolution. However, over a period of 10 to 30 years, Huntington's disease leads to loss of physical, emotional, and cognitive abilities, gradually leading to death. The condition has no cure.

Pathophysiology

In Huntington's disease, degeneration of the medium spiny neurons is seen in the corpus striatum, a part of the brain. Mutation of the HTT gene causes abnormal repetition of DNA sequence CAG. As a result, the toxic protein (large huntingtin protein) accumulates in the neurons. The number of times CAG repeats, protein accumulation in neurons increases, thus increasing the severity of the disease.