Creutzfeldt and Jakob Disease (CJD) is a rare but unique neurological disorder that effects about one in one million people each year and is the most common disease caused by prions. The term prion comes from a mixing of the words “infection” and “protein”, and is used because it is just that an infectious protein (Prusiner, 1982). Most diseases can typically be categorized based on the underlying cause of the disease, such as being bacterial, viral, or caused by genetic mutation. In the case of CJD, however, the cause of the disease is something else, it is caused by simple proteins, the building blocks of life. For context, Mad Cow disease is another type of prion disease, officially known as variant CJD.
CJD was first identified in familial studies by Hans Gerhard Creutzfeldt in 1920 and then by Alfons Maria Jakob in 1921, hence the later emergence of the name Creutzfeldt and Jakob Disease (Davison, 1940). The primary characteristics of CJD at the time were rapid neurodegeneration leading to a sudden death and, upon dissection of the victim, Spongiform Encephalopathy, or a brain with so many perforations that it looks like a sponge (Davison, 1940). After the initial identification of this disease, similar symptoms were identified around the world until similar yet different diseases started being identified Spongiform Encephalopathy eventually was reclassified as a category of diseases, and a set of symptoms were specified to differentiate CJD from the other similar diseases that had been identified. An interesting side note: it is actually speculated that some of the patients identified in Creutzfeldt and Jakob’s studies don’t actually fit into today’s standard for diagnosing CJD and therefore technically didn’t have Creutzfeldt and Jakob Disease despite Creutzfeldt and Jakob being the ones to first diagnosis it (Iwasaki, 2017).
Clinical studies on CJD and other Spongiform Encephalopathy diseases continued, showing that CJD seemingly had some genetic relation with cases of families developing the disease, but there were also many cases of isolated incidents of the disease (Friede, 1964). However, in 1968 it was discovered that, unlike any other genetic disorder previously identified, CJD could be spread to others if they were injected with infected brain matter (Gibbs, 1968). It was later shown that the mechanism that caused the initial disease was the same as the one that caused it when transferred to another animal (Prusiner, 1982). This proved that there was something fundamentally different between CJD-related diseases and other genetic based disorders. This led to a rebranding of this class of diseases to the name we use today: Transmissible Spongiform Encephalopathy (TSE) (Iwasaki, 2017).
The symptoms to diagnosis CJD are now described as minor psychological symptoms with visual and/or memory impairment leading to myoclonus, or sudden and involuntary movements (i.e. hiccups); then an akinetic mutism state, inability to move or speak; and eventually death (Iwasaki, 2017). This progression of symptoms was initially used to separate CJD from other TSE diseases and is still used today as research on the underlying reasons behind the different symptoms seen by victims of different TSE diseases is still progressing (Iwasaki, 2017).
There are currently three subdivisions of CJD based on the three different ways in which the disease has historically been caused. The 3 divisions or modes of “infection” are (i) Sporadic, or spontaneously developed, CJD (sCJD) (ii) Familial, or genetically inherited, CJD (fCJD) and (iii) Iatrogenic or transferred via a medical procedure, CJD (iCJD). Out of CJD’s prevalence of about 1 per million people, these forms represent about 85%, about 15%, and less than 1%, respectively, of cases (Iwasaki, 2017). These three subdivisions also show varying levels of morbidity and time before death.
sCJD typically develops in people without any family history of CJD between the ages of 50 to 70, usually starting as minor neurological symptoms which steadily worsens until death about 5 months after initial minor symptoms (Iwasaki, 2017).
fCJD is inherited in an autosomal dominant fashion and initial symptoms first present earlier than sCJD but tend to progress slower, leading to a similar life expectancy for both versions of CJD (Iwasaki, 2017).
iCJD is a fairly unique form of transmission for any disease as it relies on the unique properties of prion disease. iCJD specifically refers to the small subset of historical cases of CJD that were caused by prion proteins contaminating the surgical equipment used to dissect the brain of a victim of CJD. The procedure at the time to disinfect the equipment was only able to remove virus and bacteria, not the prions themselves. This allowed for the infectious proteins to remain on the equipment and enter the body of subsequent patients as they underwent surgical procedures, leading to a rapid development of CJD symptoms and usually death 1 to 2 years later (Laurenson, 1999). Shortly after this connection between CJD victim treatment and spread of the disease the WHO released guidelines focused around the proper procedure to follow when dealing with the body of a person who is even suspected of dying from a prion-based disease (WHO, 1999).
A prion, being no more than a simple protein, represents a unique infectious agent that is able to perform similar hijacking functions of Bacteria and Viruses in a host body by reproducing and spreading. Whether this infectious protein initially develops within the body or is transferred into it, the prion is able to propagate and rapidly inhibit the functionality of the brain. Because a prion is so much smaller and simpler than any other infectious agent, it is almost impossible to combat or protect against and as such, there is currently no cure or treatment for CJD or other TSE diseases.
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