Classic Creutzfeldt-Jakob disease (CJD), or mad cow disease, is a prion disease. According to the CDC, prion diseases, or transmissible spongiform encephalopathies (TSEs), are a group of diseases that cause degeneration of the nervous system of various animals and humans. The diseases are believed to be caused by prions, abnormal protein agents that cause the normal proteins in the brain to form incorrectly. Prion diseases are rare. The World Health Organization (WHO) reports that prion diseases affect less than 1 percent of the population worldwide. Yet, because of their speed of degeneration and 100 percent fatality, they have become famous. CJD is the most well-known prion disease, but there are other TSEs that affect humans.
Variant Creutzfeldt-Jakob Disease (vCJD)
Variant Creutzfeldt-Jakob disease has many symptoms similar to mad cow disease. According to the CDC, they both cause spongiform degeneration of the brain, which means that on computer scans the brain has many small holes that make it look like a sponge. Patients contract VCJD by ingesting meat products that have been contaminated by the abnormal prion. VCJD differs from classic CJD by the timing of the disease, its duration and the variance of symptoms. Classic CJD usually presents in patients who are older, approximately 68 years old, while vCJD presents in patients who are around 28 years old. The duration of classic CJD is four to five months and vCJD lasts around 13 to 14 months. The final difference is that CJD causes early onset dementia and has a focus on neurological signs, like limb paralysis. On the other hand, vCJD has more behavioral changes and psychiatric disorders and the neurological signs are more delayed.
Kuru Disease
Kuru is defined by Medline Plus as an extremely rare disease caused by an infectious protein called a prion. Prions are usually found in contaminated human brain tissue. The disease is found almost exclusively in a tribe of people in New Guinea, who practice a form of cannibalism. Among these tribes it has a prevalence rate of 2 percent. The disease has not been spread by any other means. The disease has similar symptoms to CJD. Patients experience coordination problems, difficulty walking, swallowing problems and tremors. Kuru, like most TSEs, has a long incubation period and takes 30 years or longer to develop.
Gerstmann-Straussler-Scheinker Disease (GSS)
GSS has been listed by the National Institute of Neurological Disorders and Stroke as an extremely rare neurological TSE disease that is almost always found as an inherited disease among a few families around the world. The prevalence rate is reported to be one to ten cases per 100 million people. The onset of the disease occurs between 35 to 55 years of age, and usually proves fatal to patients within 10 to 15 years. Early symptoms include lack of muscle coordination (ataxia), including difficulty walking and clumsiness. Later symptoms include dementia and worsening ataxia.
Fatal Familial Insomnia
Fatal familial insomnia is a rare inherited prion disease that is listed by Merck as a disease that interferes with the patient's sleep. The exact proportion of the disease is unknown; there have not been enough cases to properly estimate the prevalence rate in the general population. The disease leads to degeneration of the nerves and a decrease in mental and motor functions. Patients are usually 40 to 60 years old when they first experience symptoms of difficulty falling asleep and occasional tremors. As the disease progresses, the patient cannot sleep. The nervous degeneration continues until the patient passes away usually 7 to 36 months later.
