Prion Diseases

Medically Reviewed by Christopher Melinosky, MD on August 24, 2022
4 min read

Prion diseases are a group of different conditions that affect your brain and nervous system. They can cause severe dementia or problems with body control that get worse very quickly. They're rare -- the U.S. has only about 350 cases of prion diseases each year.

Prions are tiny proteins that, for some reason, fold over in a way that damages healthy brain cells. You can have them for many years before you notice any symptoms.

Prion diseases cause dementia, but not Alzheimer's disease. Different genes and proteins are involved in Alzheimer’s. But in all these diseases, including Alzheimer’s, the cause is proteins that don't work the way they should and damage brain cells.

Alzheimer's symptoms may get worse slowly and gradually over a few years. Prion diseases get worse quickly. But like Alzheimer's, there is no cure for prion diseases.

Prion diseases are also called transmissible spongiform encephalopathies, or TSEs. Both humans and animals can get them.

Prion diseases that affect people include:

  • Creutzfeldt-Jakob disease (CJD)
  • Variant Creutzfeldt-Jakob disease (VCJD)
  • Gerstmann-Straussler-Scheinker syndrome
  • Fatal familial insomnia
  • Kuru
  • Variably protease-sensitive prionopathy

Creutzfeldt-Jakob disease is the most common. It usually affects people around age 60. Variant Creutzfeldt-Jakob disease can affect younger adults.

Signs of prion diseases include sudden changes in your mood, memory, and movement, including:

Prions are tiny proteins in your brain that don't act the way they should. They fold over the wrong way, spread, and then cause other proteins to form the same incorrect shape.

These badly shaped prions build up and form clumps in your brain. Then they kill neurons, or brain cells that control your memory, balance, and movement. Your immune system can't fight them off, so more healthy cells die.

Prion disease risk factors

Most people get prion diseases like CJD for no apparent reason. Risk factors for prion diseases include:

  • Family history. Around 15% of people get prion diseases because they have a problem gene called PRNP. It can run in families.
  • Infections. Very rarely, people get prion diseases from infected tissue in a transplant operation or from unclean tools a surgeon used.
  • Eating infected meat. It's possible to get VCJD if you eat beef infected with bovine spongiform encephalopathy, or mad cow disease.

When mad cow disease broke out in cattle in Europe in the 1990s, a small number of people developed VCJD and died. Four people also got VCJD from blood transfusions when the donor was infected. To lower the risk of VCJD, countries changed how cattle are fed and how donated blood is collected and treated.

It's hard to diagnose prion diseases. If you have symptoms like dementia, your doctor might first rule out other possible causes. The following tests may show if your symptoms are caused by a stroke, brain tumor, or inflammation:

  • Spinal tap (also called lumbar puncture): A doctor puts a needle between two of your vertebrae (bones in your back) to take a sample of the fluid around your brain and spinal cord.
  • MRI (magnetic resonance imaging): Powerful magnets and radio waves are used to make detailed images of your brain.
  • CT scan (computerized tomography): Several X-rays taken from different angles are put together to show a clearer picture of your brain.

Your doctor can be certain you have a prion disease only if they take a sample of your brain tissue (called a brain biopsy). But this is a dangerous operation, so it's done only if your doctor thinks you might have another disorder that could be treated differently.

For now, treatments for prion diseases only ease your symptoms. They include:

People with prion diseases often get worse and need help taking care of themselves. You may need help with everyday activities. You also may need a catheter to help drain urine, fluids to stay hydrated, or feeding tubes to help you eat.

There’s no way to prevent prion diseases that run in families. These steps help to lower the chance of getting prion diseases from an infection or infected meat:

  • Clean and sterilize medical equipment.
  • Don’t donate tissue if you have a prion disease.
  • Make sure the meat you eat is safe.

New regulations on cows and the use of cow parts in animal feed have limited the spread of mad cow disease.