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

Medical professionals classify both conditions as neurodegenerative diseases — conditions in which a person’s brain or nerve cells gradually degrade.

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

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

Parkinson's and Huntington's differences represented by reflection of person walking.Share on Pinterest
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Parkinson’s disease and Huntington’s disease both involve the central nervous system and are neurodegenerative, which means they cause the gradual death of nerve cells.

They both involve a brain structure known as the basal ganglia and can affect a person’s movement, mental health, and cognitive (thinking) ability.

Common motor symptoms include rigidity and involuntary movements.

Rigidity is stiffness in the limbs, which makes movement challenging. The resulting inactivity can lead to pain in the muscles and joints.

Involuntary movements present as tremors in Parkinson’s disease and as chorea in Huntington’s disease. “Chorea” is the term for involuntary, irregular, dance-like movements.

There is no cure for either disease, and no currently available drugs can change the course of either disease. Available treatment options aim to relieve or reduce symptoms.

Although both Huntington’s disease and Parkinson’s disease involve the basal ganglia, the two diseases have different causes.

Parkinson’s disease results from a loss of dopaminergic neurons in a part of the brain called the substantia nigra. These neurons are specialized cells that produce dopamine, a 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 atypical protein. The expansion of the cytosine-adenine-guanine (CAG) trinucleotide in the HTT gene leads to the production of atypical 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. This means that a change in only one of a person’s 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 disease. Most people with Huntington’s disease have an affected parent.

Basal ganglia and its role

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 decreased dopamine production. Doctors do not know why this happens.

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

Sometimes, overstimulation can also happen in the motor cortex, causing chorea.

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

Huntington’s disease

Huntington’s disease can cause involuntary movements such as chorea.

Someone with Huntington’s disease will also develop significant cognitive changes and behavioral and mental health symptoms early in the progression of the disease. These can include mood changes and mental health conditions such as obsessive-compulsive disorder (OCD), bipolar disorder, and mania.

Parkinson’s disease

A person with Parkinson’s disease may first develop a tremor in their chin or in one hand. The tremor typically affects one side of the body at first but may affect both sides later in the course of the disease.

A person’s writing ability can change, and their handwriting may become small or crowded together.

People may also experience other symptoms, such as loss of smell, rigidity, or bradykinesia, which is a slow or difficult movement.

Unlike Huntington’s disease, Parkinson’s disease doesn’t cause cognitive changes until much later in its progression. On average, Parkinson’s disease also develops about 10 years later than Huntington’s disease.

There is currently no cure for either Huntington’s disease or Parkinson’s disease. Treatments aim to relieve symptoms and help people maintain the best possible quality of life.

Huntington’s disease

A person’s symptoms will determine how they manage Huntington’s disease. The American Academy of Neurology guidelines suggest using tetrabenazine (Xenazine) to treat chorea.

If a person is experiencing a mental health condition such as anxiety, depression, or OCD, doctors may prescribe selective serotonin reuptake inhibitors or tricyclic antidepressants.

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 a person’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. Doctors may also prescribe monoamine oxidase-B inhibitors.

More than 1 million people in North America and 4 million globally are living with Parkinson’s disease. In the United States, around 13 of every 100,000 people have it, and another 60,000 cases develop each year.

Late onset Parkinson’s disease is the most prevalent form of Parkinson’s disease, and the chance of developing it increases with age.

Huntington’s disease affects 3–7 of every 100,000 people with European ancestry. It tends to develop less often in people of other ancestries.

Like 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 greatly change a person’s daily life.

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

Both Alzheimer’s disease and Huntington’s disease can cause severe cognitive issues, while this 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 a person’s DNA. As doctors cannot change 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 Parkinson’s disease may also have a genetic component. However, because certain environmental factors can affect a person’s likelihood of developing Parkinson’s disease, lifestyle adjustments may reduce the chance of developing it.

For example, people can consider getting regular physical activity. According to a 2018 review, this healthy habit may help maintain the brain’s dopamine levels.

Research suggests that doctors could misdiagnose Huntington’s disease as schizophrenia because it often causes similar psychiatric symptoms before any motor symptoms develop.

A doctor could also mistake Parkinson’s disease for a few conditions, such as dementia with Lewy bodies, progressive supranuclear palsy, and multiple system atrophy.

Parkinson’s disease and Huntington’s disease are both 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, a variety of genetic and environmental factors can contribute to Parkinson’s disease.

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

There is no cure for either disease, and treatment focuses primarily on managing symptoms and treating mental health conditions that may occur, particularly in Huntington’s disease.