Prion diseases are rare and occur due to proteins in the brain that “misfold.” Another name for prion disease is transmissible spongiform encephalopathies (TSEs). There are many types of prion diseases that affect both animals and humans.
Protein folding is an important process in the body — proteins must fold into specific three-dimensional shapes to function properly. When a protein misfolds, it loses its structure and is unable to function. Misfolded proteins may cause disease in people.
Read on to learn more about prion disease, including symptoms, diagnosis, and treatment.
Prion diseases are rare, uncurable brain diseases that affect mammals, including humans.
Sometimes, the terminology to describe prion diseases can be inconsistent. “Prions” are the
When prion proteins begin to fold abnormally and clump together — called
Disease-causing prions can transmit in various ways, for example,
Some prion diseases have a rare genetic link,
When people start experiencing the effects of prion disease, their condition
Several types of prion disease can affect both humans and animals. Although experts have defined many types, it is not known for certain whether someone fits into one exact type. This is likely due to the absence of definite tests that could confirm diagnoses or rule out others.
Human prion diseases
Examples of the most common prion diseases
- Creutzfeldt-Jakob disease (CJD): This type of CJD is split into three types: familial, sporadic, and acquired. People inherit the familial type, but the sporadic type develops without any known causes. Sporadic CJD is the most common type of CJD and tends to
affectthose aged around 60 years. A person can develop acquired CJD after unsterilized medical equipment has introduced prions into the body, though this is rare.
- Variant Creutzfeldt-Jakob disease (vCJD): This type of CJD is an infectious prion disease related to mad cow disease. People acquire it by eating meat containing proteins from the brain or spinal tissue of a sick cow. Unlike sporadic CJD, vCJD is
more likelyto affect younger people.
- Fatal familial insomnia: This type — typically hereditary — is linked to inheriting an atypical form of a gene that codes for prion proteins. Rarely, this disease occurs sporadically. Over the course of the disease, people sleep less and less. This can lead to mental deterioration and physical symptoms.
- Gerstmann-Straussler-Scheinker syndrome: This is a genetic disease that affects prion proteins in the cerebellum. The cerebellum is the part of the brain that controls movement and balance, among other functions.
Animal prion diseases
Examples of common prion diseases in animals
- bovine spongiform encephalopathy, also known as mad cow disease, which affects cattle
- chronic wasting disease, which affects deer and elk
- scrapie, which affects sheep
Prion diseases are rare. The
However, risk factors for prion disease can include:
- A family history of prion disease, especially with fatal familial insomnia.
- Eating or coming into contact with meat that contains proteins from the brain or spinal tissue of a sick cow —especially with vCJD.
- Transmission — for example, acquiring the disease via medical or surgical treatment.
- Age, especially for CJD.
The symptoms of prion disease can vary, depending on the type of misfolded prion protein. Different prion proteins might target certain regions of the brain. Therefore, symptoms may be reflective of the brain areas prions are damaging.
For example, in instances of fatal familial insomnia, a person will not be able to sleep and
As prion diseases affect the brain, people generally tend to present with:
- changes in gait and walking
- muscle stiffness
- speech difficulties
- atypical jerking movements
- rapid-onset dementia
Usually, it takes a long time —
Some symptoms of prion disease
- Alzheimer’s disease
- Parkinson’s disease
- Lewy body dementia
- chronic traumatic encephalopathy, which occurs after repeated trauma to the brain
If a doctor suspects a person has prion disease, they usually also screen for the above conditions to rule them out. This is because they are more common than prion diseases.
Prion diseases are incredibly complex. Each disease has its own diagnostic criteria, usually consisting of various medical tests and physical examinations.
These can include:
- Blood tests: Detects the presence of prions in the blood. People may also be able to get prototype tests since prion diseases are so rare.
- Neurological exams: Screens for neurological damage.
- Genetic tests: Detects whether someone has gene variants.
- MRIs: Detects changes in brain structure.
- Lumbar punctures: Screens cerebral spinal fluid for certain markers for CJD.
- Electroencephalogram: Measures any changes in brain waves.
Some people may require a brain biopsy, where a doctor uses a small needle to collect a tissue sample. This is usually under a general anesthetic.
A brain biopsy is a high risk procedure as surgeons remove a part of the brain tissue. Additionally, in the case of prion disease, there are risks for anyone handling the removed sample. The best way to confirm the diagnosis for conditions such as CJD is by autopsy rather than biopsy.
Doctors can also request a sensitive diagnostic test to detect some prions or prion proteins. For example, in cases of CJD, they
People should note that the RT-QuIC assay is not widely available.
There are currently no therapies that cure prion disease. Treatment approaches may focus on treating the symptoms instead.
However, scientists are investigating the effect of different molecules that can inhibit the formation of prions. Studies are still in their
Prion diseases are rare. They affect the brain by causing prion proteins to misfold.
Some types of prion disease run in families, which a person can inherit. People can contract other types by eating affected meat or being exposed to unsterilized medical equipment that doctors have used on another person with the disease.
Symptoms of prion disease typically take time to present. However, when a person begins experiencing symptoms, they deteriorate quite quickly. There is no cure for prion disease, but scientists are looking into new ways to treat this condition.