Huntington's Disease

HD can be of three subtypes based on the age of onset:

1. Adult-onset HD: This is the most common type of HD. Symptoms usually appear in people between the ages of 30 and 50.[3]

2. Juvenile HD: This rare form of HD is seen in children and teenagers. The symptoms are similar to Parkinson's disease. Common signs of juvenile HD include:[3]

• a rapid worsening of school performance
• changes in handwriting
• slow and stiff movements
• tremors
• muscle twitching
• fits (seizures)

3. Late-onset HD: This type of HD develops in persons above 60 years of age. Chorea is the main symptom seen in people with late-onset HD.[4]

HD is caused by an alteration (also known as mutation) in the Huntingtin (HTT) gene .[5] This 

gene mutation leads to the formation of a toxic, unwanted mutant protein known as mHTT.[1] 

In HD, having one copy of the altered HTT gene is sufficient to cause the disease (autosomal 

dominance).[5]

When a person with HD has a child, there is a 50% chance that they will pass the defective 

gene to their child.[1,2,3] If the child inherits the mutated gene, they will have a high 

likelihood of developing HD at some point in their life.

On the other hand, if the child does not inherit the defective gene from their affected parent, 

they will not develop HD and cannot pass it on to their future generations.[1,2,3] When HD 

occurs without a family history, it is known as sporadic HD.[1]

If your doctor thinks that you might have HD, they will ask you about your symptoms and medical history in addition to physical examination, running certain lab tests, brain scans, and genetic testing.

• Physical examination: This may include assessment of reflexes, balance, movement, muscle tone, hearing, and walking ability.[1]
• Brain imaging: Your doctor may recommend imaging of the brain, such as computed tomography (CT) or magnetic resonance imaging (MRI). These scans usually reveal shrinkage of certain areas and enlargement of fluid-filled cavities within the brain called ventricles.[1] However, there may not be any specific changes visible on the brain scan in early stages of the disease.[3]
• Genetic testing: Genetic testing helps in predicting if you will develop HD, using DNA taken from a blood sample.[1,3] In persons showing signs of HD and who do not have a family history, a genetic test may rule out or confirm this disease.
• Prenatal testing: If there is a family history of HD, it is possible to test for the presence of faulty HTT gene already at 11 weeks of pregnancy.[3]

The course of HD can be divided into ‘premanifest’ and ‘manifest’ periods.[6]

1. Premanifest period: The period before diagnosable signs and symptoms of HD appear is called ‘premanifest’. It can be further subdivided into presymptomatic and prodromal periods.

a. Presymptomatic stage: No signs or symptoms are present.

b. Prodromal stage: It is characterized by subtle motor, cognitive and behavioural changes.

2. Manifest period: It is characterized by slow progression of motor and cognitive signs and symptoms. Fine motor skills get impaired steadily. This phase can be subdivided into three broad stages.

a. Early stage: Most areas of functioning, including working or driving can be actively performed.

b. Moderate stage: Complex functions such as working, driving or shopping independently cannot be performed, but activities of daily living and simple household tasks can be taken care of.

c. Late stage: Activities of daily living cannot be performed without help.

At the moment, there are no treatments that can cure or slow the progression of HD. The treatments currently available are used to relieve symptoms in order to improve the quality of life. The main treatments used for HD are:

Medications: While medications can help relieve some of the symptoms caused by HD, they cannot stop or slow down the disease. They include:

• Antidepressants can be used for improving mood swings and depression.[2,3]
• Mood stabilizers can help in easing mood swings and irritability.[2,3]
• Antipsychotic medications may help in managing delusions and violent outbursts, but they can cause side effects.[1,3] These drugs may also suppress involuntary movements.[1,2,3]

Always speak to your doctor about the various treatment options available and their associated side effects.

Supportive care such as assistance in performing day-to-day activities may be required.[2,3]

• Speech and language therapy - To improve communication skills and memory.
• Dietician - To work out an appropriate diet plan to prevent weight loss and prevent choking.
• Occupational therapy - To adapt your home and equipment to make life easier, such as, providing wheelchair access, installing grab rails, stairlift, using electric toothbrushes, voice-controlled devices, etc.
• Physical therapy - To help with mobility and balance.

Clinical trials (which can also be called ‘research studies’) are designed to look at how safe experimental drugs are and the mechanisms involved in slowing or potentially stopping the progression of the disease. Researchers are working hard to learn more about HD, and the cellular and molecular mechanisms involved.

Several clinical trials are underway to look at potential new treatments.

If you would like to know more about Roche sponsored clinical trials or are interested in taking part in a clinical trial, speak to your doctor or visit the Roche ForPatients clinical trials page https://forpatients.roche.com/