What Are The Causes Of Creutzfeldt-Jakob Disease (CJD)?

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Main Category: CJD / vCJD / Mad Cow Disease
Article Date: 19 Apr 2010 - 0:00 PDT


Creutzfeldt-Jakob disease (CJD) is caused by a prion - an infectious protein in the brain. The disease belongs to a broad group of animal and human diseases known as TSEs (transmissible spongiform encephalopathies). When the brain of an affected person is viewed under a microscope, it has many spongy holes, hence the use of the word "spongiform".

Proteins are made up of strings of amino acids and then fold themselves into a three-dimensional shape, which help our body cells function. The protein folding helps them perform vital functions inside the cells of our body.

Prion proteins (not the same as the infection-causing CJD ones) exist in our brains and other tissues within our nervous system. Experts believe they are key players in long-term memory, however nobody is really sure what they do.

If the protein folding does not occur correctly, the prion protein is useless. In most cases, these faultily-folded prion proteins are recycled by the body. However, they can accumulate and cause illnesses, such as Alzheimer's disease.

The misfolded prion proteins get into our brain cells and make normal proteins misfold too, resulting in the destruction of brain cells. The process is self-perpetuating, the dead brain cell releases more prions which get into other brain cells, destroying them too, etc.

At first, individual brain cells are affected, and eventually whole clusters of brain cells are destroyed and replaced with prion deposits, known as plaques. The plaques make tiny sponge-like holes in the brain - literally, the brain starts becoming like a sponge, full of holes. A spongy brain is damaged, and the patient experiences the signs and symptoms linked to CJD.

Even after an infected person or animal has died, the prions can survive in nerve tissue for a very long time.

Sporadic CJD (sCJD) - this is the most common form of CJD. Scientists do not know what triggers sCJD. They suspect a normal protein suddenly changes into a prion, or a healthy gene spontaneously becomes faulty. In the majority of cases, sCJD patients are aged over 40 years.

Variant CJD (vCJD) - the same strain of prions that cause BSE also cause VCJD. BSE stands for bovine spongiform encephalopathy, otherwise known as mad cow disease. According to a 2000 UK government inquiry, the prion is spread through cattle that have eaten mixes of meat and bone with traces of tainted spinal cords and brains. The prion made its way into processed meat products, such as hamburgers, and entered the human food chain. The UK as well as several other countries now have extremely strict controls to make sure BSE does not enter the human food chain. Cattle are no longer fed meat and bone mixes.

Experts say current controls are working. In 2000 28 people died from vCJD in the UK, compared to just two in 2009.

Some scientists believe that individuals with a specific genetic make up are more susceptible to developing vCJD when consuming contaminated processed meats. Others say that it is too early to really know how long a person has the potential to develop cCJD after eating tainted meats - it could take as long as 15 years, or even longer for symptoms to start showing.

Blood transfusions - four people in the UK are thought to have become infected because they received contaminated blood.

Iatrogenic CJD - the individual becomes infected because of surgery or medical treatment. The main cause is HGH (human growth hormone) use, used to treat children who are not growing properly. According to the NHS (National Health Service), UK, thousands of children were treated with the hormone between 1958 and 1985 - the hormones at that time were extracted from the pituitary glands of dead humans. A minute proportion of these children eventually developed CJD. Since 1985, all human growth hormone is artificially manufactured, eliminating the risk of infection.

Some patients became infected after receiving infected tissue transplants. Others were operated on with contaminated surgical instruments and eventually became ill. Prions are tough and can sometimes survive sterilization procedures focused purely on eliminating bacteria or viruses.

Inherited prion disease - the individual has inherited a faulty gene that should produce normal proteins. The mutated gene produces CJD-causing prions, experts believe. This is a dominant gene, meaning you only have to inherited one of the pair to be susceptible (all genes come in pairs).

Written by Christian Nordqvist
Copyright: Medical News Today
Not to be reproduced without permission of Medical News Today

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