Magnetic resonance imaging (MRI) of the brain of a patient with Creutzfeldt-Jakob disease. (Image credit: Pract Neurol, Mead S, Rudge PCJD mimics and chameleons Practical Neurology 2017;17:113-121, CC BY 4.0, https://creativecommons.org/licenses/by/4.0/deed.en, via Wikimedia Commons, image shown with blurred background)
Disease name: Creutzfeldt-Jakob disease (CJD), named after Hans Creutzfeldt and Alfons Jakob, two German doctors who first described the disease in the 1920s.
Affected populations: Creutzfelt-Jakob disease affects about 1 in a million people worldwide each year. In the United States, about 350 cases of the disease are reported each year. Men and women are equally affected.
Causes: CJD is caused by abnormal proteins in the brain known as “prions.” These prions cause irreversible tissue damage, resulting in spongy holes throughout the brain, causing neurons to malfunction and die. The prions start a chain reaction, causing other normal proteins in the brain to misfold. This perpetuates the condition and causes patients to experience increasingly severe problems with movement and mental function.
There are three main forms of CJD, which vary based on the mechanism by which prions are formed in the brain. The most common of these forms is “sporadic CJD,” which accounts for about 85% of cases. Sporadic CJD occurs when normal proteins spontaneously misfold and become prions for unknown reasons, with symptoms typically beginning in adults between the ages of 45 and 75.
Additionally, 10% to 15% of CJD cases are caused by a mutation in the PRNP gene that results in the formation of prions. This genetic form of the disease is inherited in an autosomal dominant manner, meaning that a child only needs to inherit one copy of the defective gene from either parent to develop the disease. The genetic form of CJD is most often seen in people between the ages of 30 and 50.
Less than 1% of CJD cases are “infectious,” meaning they are caused by the transmission of prions from an outside source. One method of transmission is by eating meat from cows infected with bovine spongiform encephalopathy, known as mad cow disease. The United States has had strict precautions in place to prevent this since the 1990s. Since the discovery in 1996 that people could become infected with CJD from mad cow disease, there have been only 233 cases worldwide.
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