Huntington's Disease

Overview

Huntington's disease is a genetic disorder that affects the brain, leading to the appearance of various physical, mental, and emotional symptoms. It appears commonly in adults around 30-50 years old, but can also affect children in rare cases. The two types of this progressive condition include adult-onset Huntington’s disease and juvenile Huntington's disease.

Symptoms include trouble with movement, memory, and mood. There is no permanent cure for the condition. However, treatment plans such as medication and therapy can help manage the symptoms and improve the quality of life of affected individuals.

What is Huntington's Disease?

Huntington's disease is an inherited disorder that causes slow functioning of the neurons (brain cells), leading to their destruction and death. This condition also affects the cells in part of the brain cortex, which is responsible for memory and regulating voluntary movement. Symptoms commonly include changes in behaviour, personality, thinking and uncontrollable movements. The symptoms eventually worsen with time.

Types of Huntington's Disease

The 2 subtypes of Huntington's disease are outlined below:

Adult-onset Huntington's Disease

The most common type that affects people in their mid-40s and 50s. Individuals in their mid or late 30s may also experience symptoms.

Juvenile Huntington's Disease

Children and teenagers develop this disease rarely. Children affected with Huntington's disease often exhibit symptoms similar to Parkinson's disease. This may make it difficult for them to attend school work effectively.

Symptoms of Huntington's Disease

Huntington's disease affects an individual mentally and physically. The symptoms one may experience mentally include difficulty learning new information, trouble reasoning or making decisions, issues with focusing, multitasking or retention. Emotional changes may include irritability, depression and mood swings.

One may experience physical symptoms such as loss of coordination (ataxia), slurred speech, difficulty walking, dysphagia difficulty swallowing and uncontrolled twitching or jerking (chorea). These physical symptoms may start with difficulty holding a pen or maintaining body balance, which eventually gets worse with time. Some other symptoms of Huntington's disease include obsessive-compulsive disorder, bipolar disorder, mania and seizures.

Causes of Huntington's Disease

Huntington’s disease is caused by a mutation in HTT genes (produces Huntingtin protein which helps neurons function) that is passed down from a carrier parent. This disease follows an autosomal dominant inheritance pattern.

A patient with this disease determines that their DNA does not have the necessary information or produce Huntingtin protein, causing abnormal growth of proteins in malignant shape. This destroys the function of neurons in the basal ganglia affecting the brain cortex and leading to the symptoms of Huntington's disease.

An individual with a parent or a family history of Huntington's disease is at an elevated risk of developing the disease themselves. Such children have a 50% chance of having genetic mutations that cause Huntington's.

Diagnosis of Huntington's Disease

A physical exam helps a neurologist understand the symptoms of the condition that has affected an individual's movements. In the process, the doctor may also ask about a family medical history of a similar disease. Following physical examination, the doctor may run some tests including blood tests and genetic testing for diagnosis. Imaging tests such as MRI and CT scans can also help with the diagnosis.

The following are the different stages of the progressive condition:

Early Stage: Individuals experience mild symptoms where they may feel moody, clumsy or struggle with complex thinking. One may continue with their daily tasks but have small uncontrollable movements.

Middle Stage: One experiences physical and mental changes, making it difficult to drive, work or do household work. They may also have problems with swallowing, speaking or eating meals. One may also lose balance, increasing their risk of falling.

End Stage: Completing everyday tasks by oneself is difficult in this stage. Proper care is required in this stage to do basic tasks such as bathing or eating.

Treatment for Huntington's Disease

Huntington's disease medication and treatment plans focus on helping an individual feel comfortable with the symptoms. While testament plans cannot stop, slow or prevent symptoms, they can help manage the severity of physical, emotional and mental symptoms.

These include medications, counselling, speech therapy, physical therapy and occupational therapy. A doctor may recommend Tetrabenazine (Xenazine®), Deutetrabenazine (Austedo®), and Haloperidol (Haldol®) to treat chorea.

Emotional symptoms can be managed with medicines such as antidepressants (fluoxetine and sertraline), antipsychotic medicines (olanzapine and risperidone), and mood-stabilising medicines (lithium).

Prevention of Huntington's Disease

One cannot prevent or reduce the risk of developing Huntington's disease. However, talking to a genetic counsellor may help if one is planning to conceive. Genetic testing can help to understand the parents’ chances of passing down the genetic mutations to their child. A doctor may also recommend in vitro fertilisation (IVF) along with genetic testing to ensure a parent does not pass the genetic mutation on to their future children.

Myths and Facts Related to Huntington's Disease

Myths and facts related to Huntington's disease are outlined below:

Myth 1: Huntington's disease is always inherited from the father
Fact: Either of the parents can pass down the faulty genes of HD to the child. However, in juvenile Huntington's disease, the father is more likely to pass down the disease to his children.

Myth 2: If a sibling has Huntington's disease, the other child may also develop the same
Fact: Children have a 50% chance of inheriting the disease from the carrier parent. Hence, another child may not inherit the disease if their sibling has it.

Myth 3: Huntington's disease is a mental disorder
Fact: While HD causes mental symptoms, it is an inherited condition that affects the brain.