Symptoms, causes, treatment and prevention

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

They are caused by abnormally folded proteins in the brain, in particular the misfolding of prion proteins (PrP).

This leads to a gradual decline in brain function, with changes in memory, behavior and movement. Ultimately, prion diseases are deadly.

About 300 new cases of prion disease are reported each year in the United States.

They can be:

  • Acquired through contaminated food or medical equipment
  • inherited through mutations in the gene encoding PrP
  • Sporadicwhere the misfolded PrP develops without any known cause

In people with prion disease, the misfolded PrP can bind to healthy PrP, causing the healthy protein to fold abnormally as well.

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

This damage creates tiny holes in brain tissue, making it look spongy under a microscope. (That’s why you may see prion diseases called “spongiform encephalopathies.”)

Researchers are still working to understand more about prion diseases and to find an effective treatment. But some things they do know.

Read on to learn about the different types of prion disease, whether there are ways to prevent them, and more.

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

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 of Creutzfeldt-Jakob disease (vCJD). This form of CJD can be contracted by eating contaminated meat from a cow.
  • Fatal familial insomnia (FFI). FFI affects the thalamus, the part of your brain that controls sleep and wake cycles. One of the main symptoms of this condition is worsening insomnia. The mutation is inherited in a dominant fashion, meaning an affected person has a 50 percent chance of passing it on to their children.
  • Gerstmann-Straussler-Scheinker syndrome (GSS). GSS is also inherited. Like FFI, it is transmitted in a dominant manner. It affects the cerebellum, the part of the brain that controls balance, coordination, and equilibrium.
  • Which. Kuru was identified in a group of people from New Guinea. The disease was transmitted through a form of ritual cannibalism that involved consuming the remains of deceased relatives.

Risk factors for these diseases include:

  • Genetics. If someone in your family has an inherited prion disease, you are also at increased risk of getting the mutation.
  • Age. Sporadic prion diseases usually develop in older adults.
  • Animal products. Consuming prion-contaminated animal products can transmit prion disease to you.
  • Medical procedures. Prion diseases can be transmitted through contaminated medical equipment and nerve tissue. Cases where this has happened include transmission through contaminated corneal grafts or dura mater grafts.

Animal prion diseases

  • Bovine spongiform encephalopathy (BSE). This type of prion disease, commonly referred to as “mad cow disease,” affects cows. People who consume meat from cows with BSE may be at risk for vCJD.
  • Chronic wasting disease (CWD). CWD affects animals such as deer, moose, and moose. It gets its name from the drastic weight loss seen in sick animals.
  • Scrapie. Scrapie is the oldest form of prion disease and has been described as far back as the 18th century. It affects animals such as 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 UK, with some also seen in other parts of Europe and Australia.
  • Transmissible mink encephalopathy (TME). This very rare form of prion disease affects minks. A mink is a small mammal that is often raised for fur production.
  • Spongiform encephalopathy of ungulates. This prion disease is also very rare and affects exotic animals related to cows.

Diseases caused by prions

The prion diseases mentioned above are not the only diseases associated with prions.

Other neurodegenerative diseases, such as Alzheimer’s and Parkinson’s disease, are also associated with misfolded proteins in the central nervous system. And research has shown that some of these misfolded proteins may be prions.

But some scientists believe that these proteins only act in a prion-like manner. They argue that they cannot be prions because the diseases they cause, such as Alzheimer’s, are not considered contagious.

Prion diseases have very long incubation times, often on the order of many years. When symptoms develop, they gradually worsen, sometimes quickly.

Common symptoms of prion disease include:

There is currently no cure for prion disease. But treatment focuses on providing supportive care.

Examples of this form of care are:

  • Medicines. Some medications may be prescribed to treat the symptoms. Examples include:
    – reducing psychological complaints with antidepressants or sedatives
    – giving pain relief with opiate medication
    – relieve muscle spasms with medicines such as sodium valproate and clonazepam
  • Assistance. As the disease progresses, many people need help to care for themselves and carry out daily activities.
  • Provides hydration and nutrients. In advanced stages of the disease, IV fluids or a feeding tube may be needed.

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

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

Since prion diseases can present with 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.

But a health care professional can use your symptoms, medical history, and various tests to diagnose prion disease.

The tests they may use include:

  • MRI. An MRI can create a detailed picture of your brain. This can help health care providers visualize changes in brain structure associated with prion disease.
  • Cerebrospinal fluid (CSF) testing. CSF can be collected and tested for markers related to neurodegeneration. There was a trial in 2015 developed to specifically detect markers of human prion disease.
  • Electroencephalography (EEG). An EEG records electrical activity in your brain. Abnormal patterns can occur in prion disease, especially with CJDwhere short periods of increased activity can be seen.

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

Some of the preventive measures taken are:

  • set strict rules for importing livestock from countries where BSE occurs
  • prohibit parts of the cow, such as the brain and spinal cord, from being used in food for humans or animals
  • prevent people with a history of or risk of exposure to prion disease from donating blood or other tissue
  • using robust sterilization measures on medical instruments that have come into contact with the nervous tissue of someone with suspected prion disease
  • destroying disposable medical instruments

There is currently no way to prevent hereditary or sporadic forms of prion disease.

If someone in your family has an inherited prion disease, consider seeing a genetic counselor to discuss your risk of developing the disease.

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

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

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

There is currently no cure for prion diseases. Instead, treatment focuses on providing supportive care and relieving symptoms.

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

Symptoms, causes, treatment and prevention

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