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Prions are a type of pathogen and the name given to the first protein found that exhibits prion-like infectious properties. Prions are a misfolded form of a host expressed protein. The misfolding allows one protein to cause the misfolding of another (the first acting as a template for the second), which will itself cause the misfolding of other proteins in a chain reaction. They are mostly known for being the transmission mechanisms for diseases that cause neurological tissues to break down in animals and humans which are known as a transmittable spongiform encephalopathies (TSE). The reason that they cause brain disease is that they are more common in brain tissue and nervous system tissue than elsewhere.

Pathology of prions[edit]

Four nerve cells in a mouse; the red parts show prion proteins, which are transmitted along neurites (projections between cells).
There are the known human diseases caused by prions: Cruetzfeldt-Jakob disease (CJD), fatal familial insomnia (FFI), kuru (transmitted by mortuary cannibalism of brain tissue), Gerstmann-Strausler syndrome (GSS), and chronic wasting disease (CWD). There are also several animal diseases caused by prions: bovine spongiform encephalopathy (BSE), feline SE (yep, your cat can get it!) and scrapie (sheep and (sobs) goats). These diseases are transmissible spongiform encephalopathies and they have varying symptoms. Normal human protein (huPrPC) is a 23 kDa water-soluble glycoprotein. When exposed to enzymes that break down other proteins (proteinases) it is chopped up into small bits (technically: it's proteinase sensitive). However, when protein folding occurs the proteins may misfold into the pathogenic/infectious form (PrPSc), then it causes disease. This has two effects, one is that the protein is no longer proteinase sensitive, in fact, it can't be destroyed short of incineration or massively powerful oxidising agents (think boiling nitric acid). Once a misfolded prion protein (PrPSc), comes into contact with normal protein prion protein (PrPC) it converts the PrPC into PrPSc (a domino effect per se). The infection is 100% lethal and it has no cure or treatment, although some people seem to have evolved a degree of resistance (most notably the Fore peopleWikipedia due to consistent encounters with kuru over several generations, some of whom went 45 years after initial contact before becoming symptomatic); a person or animal infected will die and the proteins remain infectious.

Strangely, synthetic prions do not seem to be able to cause disease in vitro unless they are in the presence of certain cofactors such as specific forms of RNA, which suggests that the current picture of prion pathogenesis is incomplete.

Several prion-like proteins have also been identified in yeasts. However, these fungal prions appear to be benign or even positive in their effects, allowing them to function as a form of epigenetic inheritable that increases variation in phenotypes among a population that would otherwise be genetically homogenous.


There are three types of prion disease — infectious, sporadic and genetic.

  • With the infectious form you get the disease by contact with infected materials or tissues. The nervous system tissue is the most infectious material. It is unknown if prion disease can be transmitted by blood but blood banks banned prion infected people from donating blood (outside of the UK — there they just gave up checking due to the expected prevalence of non-clinical infections). Transmissible also covers iatrogenic transmission (getting the disease from infected medical instruments — don't think too hard about where that endoscope went last!).
  • The sporadic form occurs at random when proteins just misfold for a reason not yet known to medical science (this is by far the most common form)
  • Then the last one are the genetic prion diseases. These prions are caused by a mutation of the PRNP protein gene; genetic prion diseases are the rarest out of the three of them. The most notable genetic prion disease is Fatal Familial Insomnia, a genetic disorder present in only 30 families worldwide. In animals it seems that corpses transmits prion disease and unlike in humans prions are 100% lethal.

Signs and symptoms of prion disease[edit]

Prion diseases are always degenerative, and eventually lead to death. Signs and symptoms vary among each disease but are very similar. This section will give lists of the symptoms of a few of these diseases.

Cruetzfeldt-Jakob Disease

  • Memory loss
  • Loss of motor function
  • Slurred speech
  • Vision loss


  • Loss of motor function
  • Trouble walking
  • Memory loss
  • Mood swings
  • Trouble swallowing
  • Slurred Speech
  • Bouts of alternating between laughing (which is always quite mirthless) and crying, hence the common name laughing sickness

Fatal Familial Insomnia

  • Insomnia, eventually to the extent where sleep is completely impossible
  • Ataxia
  • Hallucinations
  • Loss of motor skills
  • Slurred speech

Many medical professionals have never even heard of prions because they are so rare.


As with any deadly disease, there are quacks who promote woo. Earth Clinic, which is a natural health website, claims that apple cider vinegar and caprylic acid can treat the symptoms.[1] However, if someone ingests too much caprylic acid it may cause pain in the gastrointestinal tract. Caprylic acid is fairly safe if taken in small amounts; outside that it does nothing to help with symptoms.

See also[edit]

External links[edit]