Prion Diseases

What are prion diseases?

Prion diseases comprise several conditions. A prion is a type of protein that can trigger normal proteins in the brain to fold abnormally. Prion diseases can affect both humans and animals and are sometimes transmitted to humans by infected meat products. The most common form of prion disease that affects humans is Creutzfeldt-Jakob disease (CJD).

Prion diseases are rare. About 300 cases are reported each year in the U.S.

Types of prion diseases include:

  • CJD. A person can inherit this condition, in which case it's called familial CJD. Sporadic CJD, on the other hand, develops suddenly without any known risk factors. Most cases of CJD are sporadic and tend to strike people around age 60. Symptoms of CJD (see below) quickly lead to severe disability and death. In most cases, death occurs within a year.  
  • Variant CJD. This is an infectious type of the disease that is related to “mad cow disease.” Eating diseased meat may cause the disease in humans. The meat may cause normal human prion protein to develop abnormally. The disease is also thought to spread to people receiving cornea transplants from infected donors and from contaminated medical equipment. This type of the disease usually affects younger people.
  • Variably protease-sensitive prionopathy (VPSPr). This is also extremely rare, it is similar to CJD but the protein is less sensitive to digestion. It is more likely to strike people around age 70 who have a family history of dementia.  
  • Gerstmann-Sträussler-Scheinker disease (GSS). Extremely rare, but occurs at an earlier age, typically around age 40.
  • Kuru. This disease is seen in New Guinea. It's caused by eating human brain tissue contaminated with infectious prions. Because of increased awareness about the disease and how it is transmitted, kuru is now rare.
  • Fatal insomnia (FI). Rare hereditary disorder causing difficulty sleeping.

What causes prion disease?

Prion diseases occur when normal prion protein, found on the surface of many cells, becomes abnormal and clump in the brain, causing brain damage. This abnormal accumulation of protein in the brain can cause memory impairment, personality changes, and difficulties with movement. Experts still don't know a lot about prion diseases, but unfortunately, these disorders are generally fatal.

Who is at risk for prion diseases?

  • Family history of prion disease
  • Eating meat infected by “mad cow disease”
  • Infection from receiving contaminated corneas or from contaminated medical equipment

What are the symptoms of prion diseases?

Symptoms of prion diseases include:

  • Rapidly developing dementia
  • Difficulty walking and changes in gait
  • Hallucinations
  • Muscle stiffness
  • Confusion
  • Fatigue
  • Difficulty speaking

How are prion diseases diagnosed?

Prion diseases are confirmed by taking a sample of brain tissue during a biopsy or after death. Health care providers, however, can do a number of tests before to help diagnose prion diseases such as CJD, or to rule out other diseases with similar symptoms. Prion diseases should be considered in all patients with rapidly progressive dementia.

The tests include:

  • MRI (magnetic resonance imaging) scans of the brain
  • Samples of fluid from the spinal cord (spinal tap, also called lumbar puncture)


  • Electroencephalogram, which analyzes brain waves; this painless test requires placing electrodes on the scalp
  • Blood tests
  • Neurologic and visual examinations to evaluate for nerve damage and vision loss

How are prion diseases treated?

Prion diseases can't be cured, but certain medications may help slow their progress. Medical management focuses on keeping people with these diseases as safe and comfortable as possible, despite progressive and debilitating symptoms.

Can prion diseases be prevented?

Properly sterilizing medical equipment may prevent the spread of the disease. If you have or may have CJD, you should not donate organs or tissue, including corneal tissue. Newer regulations that govern the handling and feeding of cows may help prevent the spread of prion diseases.

Living with prion diseases

As prion diseases progress, people with these diseases generally need help taking care of themselves. In some cases they may be able to stay in their homes, but they eventually may need to move to a care facility.

Key points

  • Prion diseases are very rare
  • Symptoms can progress rapidly requiring help with daily needs
  • Prion diseases are always fatal

Next steps

Tips to help you get the most from a visit to your health care provider:

  • Before your visit, write down questions you want answered.
  • Bring someone with you to help you ask questions and remember what your provider tells you.
  • At the visit, write down the names of new medicines, treatments, or tests, and any new instructions your provider gives you.
  • If you have a follow-up appointment, write down the date, time, and purpose for that visit.
  • Know how you can contact your provider if you have questions.

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