Prion Disease - the Infectious Disease Few People Know

If you’re wondering why you haven’t heard of prions before, that’s probably because they’re a relatively recent discovery. Major research into prions and how they work only began in the late 1990s.

Simply put, prions (pronounced as pry-ons in British English and pree-ons in the US) are misshapen, or misfolded, proteins. Unlike any other known infectious agent, prions don’t have DNA or RNA of their own. But they can trigger the healthy proteins that make up the human body to change their shape, which leads to a cascade of degenerative protein changes known as prion disease.

Although not very common, prion diseases occur every year, with around 300 cases being recorded annually in the US alone. Most prion diseases affect the brain, which leads to a gradual cognitive and general neurological decline that resembles dementia, and eventually death (sometimes as quickly as a few months).

Another difference between prion disease and other infectious agents lies in the way one can get the disease. On one hand, you could acquire prion disease much like the stomach flu: through food contamination or dirty medical equipment. But prion disease can also be hereditary or absolutely spontaneous. The sporadic form of prion disease is the most common one, and it is more widespread in older adults.

And as if that wasn’t enough, it gets even scarier because, when prion disease develops, it can infect others - whatever the initial cause. Medical researchers are not sure why prions occur and don’t have an effective treatment for prion disease.

Medicine currently recognizes 5 major prion diseases in humans: 

• Fatal familial insomnia (FFI) - a rare genetic brain disease that damages the brain region called the thalamus and causes severe insomnia. As a result, significant physical and mental damage occurs. A parent has a 50% chance of passing FFI down to their children.
• Creutzfeldt-Jakob disease (CJD) - usually sporadic but can also be genetic or acquired. This neurodegenerative prion disease is characterized by rapid progression.
• Variant Creutzfeldt-Jakob disease (vCJD) - also known as mad cow disease, it’s an infectious disease that spreads from animals to humans through consuming the meat of infected animals.
• Kuru - infectious prion disease observed among participants in cannibalistic rituals in New Guinea.
• Gerstmann-Straussler-Scheinker syndrome (GSS) - an extremely rare type of early-onset dementia that usually runs in families and affects the cerebellum.

Symptoms of prion diseases

One more scary fact about prion disease is that it can linger in the body for a long time before causing any symptoms. This incubation period can last for 5 to 20 years. Once detected, symptoms usually get progressively and often rapidly worse. 

Unlike other infectious agents like bacteria or viruses, all currently-known prions seem to target the nervous system exclusively. The majority of prion diseases create holes in brain tissue, causing a condition called spongiform encephalopathy. Dementia-like symptoms are very common in patients with prion diseases, namely:

- problems with memory and thinking
- abnormal involuntary movements
- loss of coordination (ataxia)
- insomnia
- slurred speech
- vision problems
- personality changes
- disorientation and confusion.

However, since different prion diseases affect various parts of the brain, symptoms can be quite different. A diagnosis is usually made by conducting brain imaging, bloodwork, and cerebrospinal fluid testing.

Currently, no treatments of prion diseases exist. Doctors can prescribe patients who suffer from a prion disease pain relief drugs, muscle spasm medication, antidepressants, or sedatives. Researchers continue studying prion diseases and searching for potential cures and treatments.

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