Prion diseases are a group of neurodegenerative disorders that can affect both humans and animals.

They’re caused by the the deposition of abnormally folded proteins in the brain, which can cause changes in:

  • memory
  • behavior
  • movement

Prion diseases are very rare. Approximately 350 new cases of prion disease are reported each year in the United States.

Researchers are still working to understand more about these diseases and to find an effective treatment. Currently, prion diseases are always eventually fatal.

What are the different types of prion disease? How can you develop them? And is there any way to prevent them?

Continue reading to discover the answers to these questions and more.

Prion diseases cause a progressive decline in brain function due to misfolding of proteins in the brain — particularly the misfolding of proteins called prion proteins (PrP).

The normal function of these proteins is currently unknown.

In people with prion disease, misfolded PrP can bind to healthy PrP, which causes the healthy protein to also fold abnormally.

Misfolded PrP begins to accumulate and form clumps within the brain, damaging and killing nerve cells.

This damage causes tiny holes to form in brain tissue, making it appear sponge-like under a microscope. In fact, you may also see prion diseases referred to as “spongiform encephalopathies.”

You can develop a prion disease in several different ways, which may include:

  • Acquired. Exposure to abnormal PrP from an outside source may occur through contaminated food or medical equipment.
  • Inherited. Mutations present in the gene that codes for PrP leads to the production of misfolded PrP.
  • Sporadic. Misfolded PrP may develop without any known cause.

Prion disease can occur in both humans and in animals. Below are some different types of prion diseases. More information about each disease follows the table.

Human prion diseasesAnimal prion diseases
Creutzfeldt-Jakob disease (CJD)Bovine spongiform encephalopathy (BSE)
Variant Creutzfeldt-Jakob disease (vCJD)Chronic wasting disease (CWD)
Fatal Familial insomnia (FFI)Scrapie
Gerstmann-Straussler-Scheinker syndrome (GSS)Feline spongiform encephalopathy (FSE)
KuruTransmissible mink encephalopathy (TME)
Ungulate spongiform encephalopathy

Human prion diseases

  • Creutzfeldt-Jakob disease (CJD). First described in 1920, CJD can be acquired, inherited, or sporadic. Most cases of CJD are sporadic.
  • Variant Creutzfeldt-Jakob disease (vCJD). This form of CJD can be acquired through eating the contaminated meat of a cow.
  • Fatal Familial insomnia (FFI). FFI affects the thalamus, which is the part of your brain that manages sleeping and waking cycles. One of the main symptoms of this condition is worsening insomnia. The mutation is inherited in a dominant manner, meaning an affected person has a 50 percent chance of transmitting it to their children.
  • Gerstmann-Straussler-Scheinker syndrome (GSS). GSS is also inherited. Like FFI, it’s transmitted in a dominant manner. It affects the cerebellum, which is the part of the brain that manages balance, coordination, and equilibrium.
  • Kuru. Kuru was identified in a group of people from New Guinea. The disease was transmitted via a form of ritual cannibalism in which the remains of deceased relatives were consumed.

Animal prion diseases

  • Bovine spongiform encephalopathy (BSE). Commonly called “mad cow disease,” this type of prion disease affects cows. Humans who consume meat from cows with BSE can be at risk for vCJD.
  • Chronic wasting disease (CWD). CWD affects animals like deer, moose, and elk. It gets its name from the drastic weight loss observed in sick animals.
  • Scrapie. Scrapie is the oldest form of prion disease, having been described as far back as the 1700s. It affects animals like sheep and goats.
  • Feline spongiform encephalopathy (FSE). FSE affects domestic cats and wild cats in captivity. Many of the cases of FSE have occurred in the United Kingdom and Europe.
  • Transmissible mink encephalopathy (TME). This very rare form of prion disease affects mink. A mink is a small mammal that’s often raised for fur production.
  • Ungulate spongiform encephalopathy. This prion disease is also very rare and affects exotic animals that are related to cows.

Several factors can put you at risk of developing a prion disease. These include:

  • Genetics. If someone in your family has an inherited prion disease, you’re at an increased risk of also having the mutation.
  • Age. Sporadic prion diseases tend to develop in older adults.
  • Animal products. Consuming animal products that are contaminated with a prion can transmit a prion disease to you.
  • Medical procedures. Prion diseases can be transmitted through contaminated medical equipment and nervous tissue. Cases where this has happened include transmission through contaminated cornea transplants or dura mater grafts.

Prion diseases have very long incubation periods, often on the order of many years. When symptoms develop, they progressively worsen, sometimes rapidly.

Common symptoms of prion disease include:

Since prion diseases can present similar symptoms to other neurodegenerative disorders, they can be difficult to diagnose.

The only way to confirm a diagnosis of prion disease is through a brain biopsy performed after death.

However, a healthcare provider can use your symptoms, medical history, and several tests to help diagnose prion disease.

The tests they may use include:

  • Magnetic resonance imaging (MRI). An MRI can create a detailed image of your brain. This can help healthcare providers visualize changes in brain structure that are associated with prion disease.
  • Cerebrospinal fluid (CSF) testing. CSF can be collected and tested for markers associated with neurodegeneration. In 2015, a test was developed to specifically detect markers of human prion disease.
  • Electroencephalography (EEG). This test records electrical activity in your brain.

There’s currently no cure for prion disease. However, treatment focuses on providing supportive care.

Examples of this type of care include:

  • Medications. Some medications can be prescribed to help treat symptoms. Examples include:
    – reducing psychological symptoms with antidepressants or sedatives
    – providing pain relief using opiate medication
    – easing muscle spasms with drugs like sodium valproate and clonazepam
  • Assistance. As the disease advances, many people need help taking care of themselves and performing daily activities.
  • Providing hydration and nutrients. In advanced stages of the disease, IV fluids or a feeding tube may be required.

Scientists continue to work to find an effective treatment for prion diseases.

Some of the potential therapies that are being investigated include use of anti-prion antibodies and “anti-prions” that inhibit replication of abnormal PrP.

Several measures have been taken to prevent the transmission of acquired prion diseases. Because of these proactive steps, acquiring a prion disease from food or from a medical setting is now extremely rare.

Some of the preventive steps taken include:

  • setting tight regulations on importing cattle from countries where BSE occurs
  • prohibiting the parts of the cow such as the brain and spinal cord from being used in food for humans or animals
  • preventing those with a history of or risk for exposure to prion disease from donating blood or other tissues
  • using robust sterilization measures on medical instrument that has come into contact with the nervous tissue of someone with suspected prion disease
  • destroying disposable medical instruments

There’s currently no way to prevent inherited or sporadic forms of prion disease.

If someone in your family has had an inherited prion disease, you may consider consulting with a genetic counselor to discuss your risk of developing the disease.

Prion diseases are a rare group of neurodegenerative disorders caused by abnormally folded protein in your brain.

The misfolded protein forms clumps that damage nerve cells, leading to a progressive decline in brain function.

Some prion diseases are genetically transmitted, while others can be acquired through contaminated food or medical equipment. Other prion diseases develop without any known cause.

There’s currently no cure for prion diseases. Instead, treatment focuses on providing supportive care and easing symptoms.

Researchers continue to work to discover more about these diseases and to develop potential treatments.