Prion Disease - the Infectious Disease Few People Know
We’ve all heard of bacteria, fungi, and
viruses. These microscopic organisms can be beneficial to humans, or
they can get into human cells and cause an infection. But there’s one
less-known infectious agent that doesn’t fit in any of these three
categories - prions. These poorly understood disease-causing agents
trigger neurodegenerative brain diseases, and everyone should learn what
they are.
What are prion diseases?
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.
Types of 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.
Prion Disease woman with headache
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.