Alzheimer's and Creutzfeldt-Jakob disease are two different types of dementia that both involve protein folding problems. However, they stem from completely different protein disorders and also manifest with very different symptoms. In addition, Creutzfeldt-Jakob can be contagious, whereas Alzheimer's is not.
Identification
Alzheimer's and Creutzfeldt-Jakob disease have several similarities. They are both neurological disorders, and they misfolding, but the similarities stop there. Proteins have a certain folded structure, which generally determines how they work. Protein misfolding diseases are unique in that a protein folds away from its usual conformation and instead folds differently, causing a loss of function of the protein and, at times, toxicity. Protein misfolding diseases are often complicated by the fact that one misfolded protein can cause other proteins around it to fold incorrectly, propagating the disease.
Types
Alzheimer's disease is caused by a misfolding of the beta-amyloid protein, a protein normally found in the brain with no known function. Alzheimer's can arise spontaneously, as a natural course of aging, or it can arise due to a mutant beta-amyloid protein. While it is not known exactly what causes the protein to misfold, there are certain genetic and environmental factors that are associated with a heightened risk for the disease.
Effects
The symptoms of Alzheimer's disease begin with memory loss, which is normally thought to be age and stress related. As the disease progresses, additional symptoms appear, such as confusion, irritability and, in severe cases, hallucinations. Once a diagnosis of Alzheimer's is made, often using a brain scan and other cognitive and behavioral tests, the average survival time is roughly 7 years.
Types
Creutzfeldt-Jakob is the most common transmissible type of spongioform encephalopathy, a type of brain disease that causes small holes to form in the brain, making it resemble a sponge. Creutzfeldt-Jakob is thought to be a prion disease, which is a rare type of misfolded protein that can confer a disease (most other diseases are spread via bacteria, viruses, or parasites). Creutzfeldt-Jakob is more commonly known as "mad-cow," in which the disease was spread via the ingestion of brain tissue from infected cows, though the disease can also be spread via consumption of brain tissue from other animals. The disease can also be a result of a genetic mutation in the prion protein, though this only accounts for less than 10 percent of the known cases.
Effects
The primary symptom of Creutzfeldt-Jakob is a dementia that rapidly progresses, along with involuntary muscle movements, speech problems and hallucinations. In most cases of sporadic (i.e. not genetically inherited), the disease is fatal within a matter of months. Once Creutzfeldt-Jakob is suspected, in can usually be confirmed with an EEG (an electroencephalogram, a type of brain scan that shows a typical pattern for Creutzfeldt-Jakob), analysis of the cerebrospinal fluid, and certain characteristic markings on an MRI.
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