Overview of Creutzfeldt-Jakob Disease (CJD)
Creutzfeldt-Jakob disease (CJD) is one of a group of progressive neurological diseases called transmissible spongiform encephalopathies (TSEs). TSEs, which can affect humans and animals, cause brain tissue to become so filled with holes that it resembles a sponge upon microscopic examination.
Transmissible spongiform encephalopathies are also called prion diseases. Prions are proteins that lack nucleic acids (e.g., DNA, RNA), which are complex compounds present in all other living cells. Prions occur in a normal, harmless form, and in an infectious form, which causes disease. Prion diseases occur when infectious prions bind to normal proteins in the central nervous system and cause abnormal cell conformation.
Prion diseases can occur in animals that consume prion-contaminated food. These diseases include scrapie, which occurs in sheep and goats, and bovine spongiform encephalopathy (BSE), which occurs in cows and is also called "mad cow disease."
Transmission of prion diseases from one species to another is not fully understood, but it can occur. Variant CJD (vCJD) is an acquired disease that develops in people who ingest beef from cattle with BSE. Outbreaks of mad cow disease can result in cases of vCJD in people.
Types of Creutzfeldt-Jakob Disease (CJD)
There are three general types of CJD: sporadic, familial, and acquired (e.g., vCJD). Sporadic CJD (sCJD) occurs with no known risk factors and is the most common type. It accounts for at least 85 percent of cases.
Familial CJD (fCJD) occurs as a result of an inherited genetic abnormality. This type accounts for 5–15 percent of cases and is similar to other inherited neurological diseases such as Gerstmann-Straussler-Sheinker disease (GSS) and fatal familial insomnia (FFI).
Rarely, CJD is acquired as a result of a medical procedure or treatment (e.g., organ or tissue transplant, graft, human growth hormone [hGH] therapy) that exposes the central nervous system to prion-contaminated tissue or medical instruments. This type accounts for less than 1 percent of cases and is called iatrogenic CJD (iCJD).
Incidence and Prevalence of CJD
According to the National Institutes of Health (NIH), Creutzfeldt-Jakob disease is rare and occurs in 1 out of every 1 million people worldwide. It usually develops between the ages of 50 and 75, and the average age of onset is 60 years. Variant CJD is more common in younger patients.