What are Prion Diseases and How Do they Affect Humans

Prion diseases are a group of rare, fatal neurological disorders caused by an infectious agent called prions. Prions are pieces of protein that can change into a different shape which has the potential to lead to cellular damage and death.

A common misconception is that prion diseases are the result of a virus, but in reality they are caused by misfolded proteins that destroy brain cells and cause these diseases. Prion diseases can affect humans in more ways than just physical symptoms like dementia and memory loss; they also affect social interactions such as communication skills and moods.

The most common types of prion disease include Creutzfeldt-Jakob disease (CJD), Kuru, Fatal Familial Insomnia (FFI) and Gerstmann-Straussler-Scheinker Syndrome.

What is Creutzfeldt-Jakob disease (CJD)

Creutzfeldt-Jakob disease (CJD) is a rare, fatal brain disorder. It belongs to a group of disorders known as transmissible spongiform encephalopathies. These diseases are progressive and typically lead to death within a year or two of onset. CJD is the only human form of Creutzfeldt-Jakob disease currently known.

Symptoms of Creutzfeldt-Jakob disease (CJD)

The most common symptom of Creutzfeldt-Jakob Disease is memory loss, followed by rapidly progressive dementia. Other symptoms include:

  • Hallucinations
  • Incoordination
  • Unsteady Gait
  • Poor coordination
  • Personality Change
  • Jerky or sudden movements

Types of Creutzfeldt-Jakob disease (CJD)

There are four types of CJD identified based on the mode of transmission:

  • Sporadic Creutzfeldt-Jakob Disease – Sporadic Creutzfeldt-Jakob disease (sCJD) has no clear-cut cause. However, scientists speculate that the normal brain protein may abnormally fold, thereby turning into a prion. This type of CJD is more common among individuals who are aged between 45 and 75. However, this type of CJD still remains the rarest type
  • Variant CJD (vCJD) – This variant of CJD is most likely to be caused by consuming cattle that had a prion disease called bovine spongiform encephalopathy (BSE). vCJD can also be transmitted through blood transfusion.
  • Familial or inherited CJD – This type of CJD is caused when a person carries a mutated gene (prion protein gene) that they inherited from their parent and the symptoms of CJD begin to manifest during adulthood.
  • Iatrogenic CJD – A form of CJD which can be spread through improperly sterilized surgical instruments that have been used on a CJD’ patient’s brain. It can also be transmitted through certain medical treatments – In the past, human pituitary growth hormones were extracted from deceased individuals for growth hormone treatment. In some cases, these deceased individuals were infected with CJD.

Treatment for Creutzfeldt-Jakob disease (CJD)

Currently, there is no cure for CJD, so the main goal of treatment is to control symptoms and improve quality of life.

What is Kuru?

Kuru is a prion disease that is transmitted through ritualistic cannibalism and the mean incubation period is 10 years. This condition was first noticed among the Fore people of Papua New Guinea. It was also called “laughing sickness” as pathological bursts of laughter was a symptom of this disease. Like other prion diseases, Kuru is a progressive neurodegenerative disorder that begins with muscle spasms and shakes, followed by major physical disability and eventual death. The first symptoms might be a slight tremor in one arm or leg, which gets worse over time. Patients will start to have difficulty speaking clearly, they may have trouble swallowing and chewing food, and their arms will become weak. They may eventually be unable to stand or walk without support due to progressive muscle weakness.

What are the Symptoms of Kuru Disease

The most common initial symptom is involuntary, progressive, symmetrical jerking of the limbs, trunk, and neck muscles.In later stages of the disease, patients experience difficulty speaking, walking and swallowing. Other symptoms include:

  • Loss of coordination
  • Weakness in extremities
  • Pain in the arms and legs
  • Severe problems with coordination
  • Walking difficulties
  • Headache
  • Difficulty in swallowing
  • Tremors
  • Muscle jerks

Outlook on Kuru

Death usually occurs within one year of the onset of symptoms. However, Kuru is a rare disease and the chances of being infected are quite slim. Moreover, diagnosis usually involves ruling out other diseases of the nervous system.

Treatment

Like other prion diseases, Kuru has no treatments.

What is Fatal Familial Insomnia (FFI)

Fatal familial insomnia (FFI) is a rare genetic, degenerative prion disease that causes dementia and eventually death. It is characterized by a progressive deterioration of the brain’s cortex and thalamus regions, as well as the loss of neurons in these regions. The disease can be passed onto offspring, but may not show until adulthood – it has an incubation period of 10-30 years.

The disease is caused by a mutation to the PRNP gene. Symptoms include extreme exhaustion, inability to sleep, difficulty in concentration and confusion. FFI progresses slowly over time until the patient can no longer function and dies.

What are the Symptoms of Fatal Familial Insomnia?

Following are some of the known symptoms of FFI:

  • Short-term memory loss
  • Uncoordinated movements
  • Difficulty in thinking
  • Difficulty in concentrating
  • Insomnia
  • Hallucinations
  • Delirium
  • Excessive sweating
  • Difficulty in coordinating movements
  • Inability to maintain body temperature

Treatment of Fatal Familial Insomnia

As stated previously, prion diseases are currently untreatable. Hence, treatment, if any, is focused on controlling symptoms and improving quality of life.

Gerstmann-Straussler-Scheinker Syndrome

Gerstmann-Straussler-Scheinker Syndrome is an extremely rare, inherited disorder that causes progressive damage to the brain and nervous system. Interestingly, this condition is exclusively heritable and is found only across a few families around the world. Symptoms include memory loss, difficulty walking, blindness and seizures. The disease is also characterized by an inability to recognize faces, read words, or write coherently. Gerstmann-Straussler-Scheinker syndrome is most often diagnosed between 20-60 years of age.

What are the Symptoms of this Disease?

Following are known symptoms of this disease:

  • Patients develops Ataxia and it become more pronounced as the disease progresses
  • Patients may also experience Dysarthria or slurred speech
  • Other symptoms include involuntary movements of the eyes (nystagmus)
  • Spasticity (rigid muscle tone)
  • Might lead to blindness
  • Deafness may also occur

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