Parkinson’s disease and Huntington’s disease both involve the central nervous system. As a result, they affect how brain cells work, leading to symptoms such as tremors, limb stiffness, difficulty walking or talking, and cognitive or thinking problems.

The medical profession classifies both conditions as neurodegenerative diseases, which is the term for conditions in which an individual’s brain or nerve cells gradually deteriorate.

However, although Parkinson’s disease and Huntington’s disease may cause similar symptoms, there are differences between them.

Huntington’s disease is an inherited condition resulting from genetic changes that pass down from parent to child. Conversely, experts believe that a combination of environmental and genetic factors contributes to Parkinson’s disease.

This article looks at the similarities and differences between Parkinson’s disease and Huntington’s disease and considers how both conditions compare with Alzheimer’s disease.

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Parkinson’s disease and Huntington’s disease both involve the central nervous system and are neurodegenerative, meaning that they cause the gradual death of nerve cells.

They both involve a brain structure known as the basal ganglia and can affect an individual’s movement, mental health, and cognitive or thinking abilities.

Common motor symptoms include rigidity and involuntary movements. Rigidity refers to stiffness in the limbs, which makes it challenging to move. The resulting inactivity can cause an individual to experience pain in their muscles and joints. Meanwhile, involuntary movements present as tremors in Parkinson’s and chorea in Huntington’s. Chorea is the term for involuntary, unpredictable, dance-like movements.

There is no cure for either condition, and no currently available drugs can modify the disease courses. Therefore, treatment options aim to provide relief from the symptoms.

Although both Huntington’s disease and Parkinson’s disease involve the basal ganglia, the causes of each disease are different.

Parkinson’s disease results from losing dopaminergic neurons in a particular part of the brain called the substantia nigra. These neurons are specialized cells that produce dopamine, a type of neurotransmitter that helps nerves communicate. Experts think that a combination of genetic and environmental factors causes Parkinson’s disease.

Huntington’s disease is genetic, involving the Huntingtin (HTT) gene. The affected gene produces abnormal protein. It is the expansion of the cytosine-adenine-guanine (CAG) trinucleotide in the HTT gene that leads to the production of abnormal protein. The higher the number of CAG repeats, the earlier the age of onset and the greater the severity of the disease.

Furthermore, Huntington’s disease is an autosomal dominant disorder, meaning that a change in only one of the two copies of the HTT gene can cause the disease. When someone with Huntington’s disease has children, each child has a 1 in 2 chance of inheriting the mutated gene and developing the condition. Most people with Huntington’s disease have an affected parent.

Parkinson’s disease affects a part of the brain’s basal ganglia known as the substantia nigra. The substantia nigra creates dopamine, a neurotransmitter that maintains communication between the nerves.

Dopamine and another neurotransmitter, acetylcholine, are involved in movement. In Parkinson’s disease, the progressive death of cells in the substantia nigra leads to lowered dopamine production. Doctors do not know why this happens.

The reduced level of dopamine creates an imbalance between dopamine and acetylcholine. This imbalance disrupts healthy communication between nerves and leads to uncontrolled motor symptoms.

Sometimes, overstimulation can also happen in the motor cortex, causing irregular, jerky movements known as chorea.

Both Huntington’s disease and Parkinson’s disease cause symptoms that can severely affect an individual’s life, but there are some differences between the two conditions.

Huntington’s disease

Huntington’s disease can cause movement problems, including chorea, which refers to unusual jerking and writhing movements.

Someone with Huntington’s disease will eventually have cognitive changes and behavioral and mental health symptoms. They might have difficulties with:

  • organization
  • impulse control
  • self-awareness
  • thought and word processing
  • learning

Additionally, mood problems may manifest as:

Individuals may also develop obsessive-compulsive disorder (OCD), bipolar disorder, and mania.

Parkinson’s disease

Individuals with Parkinson’s disease may initially develop a tremor in their chin or in one hand. The tremor typically affects one side of the body first, but later in the disease, it may affect both sides.

The way an individual writes can also change, and their handwriting may become small or crowded together.

People may also experience other symptoms, such as:

  • loss of smell
  • hunching over
  • rigidity
  • bradykinesia, which is slow or difficult movement
  • hypophonia, or a soft voice
  • sleep abnormalities, such as REM sleep behavior disorder, restless leg syndrome, daytime sleepiness, and sleep attacks

Bradykinesia can manifest in various ways. An individual may have difficulty starting an action, such as getting out of bed. Any physical activity can also become slow, making it difficult for those with Parkinson’s disease to perform daily tasks.

As there is currently no cure for either Huntington’s disease or Parkinson’s disease, treatments aim to relieve the individual’s symptoms and help them maintain the best possible quality of life.

Huntington’s disease

A person’s symptoms will determine how they manage their Huntington’s disease. The American Academy of Neurology (AAN) guidelines suggest using tetrabenazine (Xenazine), amantadine (Gocovri), or riluzole (Rilutek) to treat chorea.

If the individual is experiencing mental health problems, such as anxiety, depression, or OCD, doctors may prescribe selective serotonin reuptake inhibitors (SSRIs) or tricyclic antidepressants (TCAs).

Parkinson’s disease

There is no single standard treatment for Parkinson’s disease and none that can reverse the effects of the disease. Instead, doctors base their recommendations on an individual’s symptoms.

There are many medications that doctors may use to ease symptoms, and levodopa (Sinemet) is the primary treatment. Other medications called dopamine agonists may delay the onset of motor complications, and doctors may also prescribe monoamine oxidase-B inhibitors.

As with Huntington’s disease and Parkinson’s disease, Alzheimer’s disease is a neurodegenerative condition affecting the brain. All three diseases can cause debilitating effects and impact an individual’s daily life.

However, Alzheimer’s disease primarily affects an individual’s memory, thoughts, and behavior and does not affect movement as markedly as Huntington’s disease and Parkinson’s disease.

Like Alzheimer’s disease, Huntington’s disease can also cause severe cognitive issues, which is not a primary feature of Parkinson’s disease.

No, it is not possible to prevent these conditions.

Huntington’s disease is a hereditary disorder that involves a mutation in an individual’s DNA. As doctors cannot alter a person’s genetic makeup, they cannot prevent the disease. Additionally, no therapies are currently available that can stop or slow the progression of Huntington’s disease.

Experts think that Parkinson’s disease may also have a genetic component. However, because certain environmental factors can affect an individual’s likelihood of developing the condition, lifestyle adjustments may reduce the risk. These may include:

  • avoiding toxins
  • avoiding pesticides
  • avoiding exposure to metals
  • protecting against traumatic brain injuries

Individuals should also consider getting regular physical exercise as, according to a 2018 review, this healthy habit may help maintain the brain’s dopamine levels.

Parkinson’s disease and Huntington’s disease are neurodegenerative conditions involving the basal ganglia area of the brain.

Huntington’s disease is genetic and results from a mutated gene that a person usually inherits from a parent. In contrast, Parkinson’s disease can occur due to a variety of genetic and environmental factors.

Both conditions involve involuntary motor symptoms. In Parkinson’s disease, people may experience rigidity and slowed movements, while in Huntington’s disease, individuals may also experience cognitive and psychological symptoms.

There are no cures for either disease, and treatment focuses primarily on helping ease symptoms and treating mental health problems that may occur, particularly with Huntington’s disease.