Creutzfeldt-Jakob disease (CJD) is a rare, degenerative, invariably fatal brain disorder.1

Although the agent of sporadic CJD (sCJD), the most common type of CJD, differs from the agent of bovine spongiform encephalopathy (BSE) or “mad cow disease”, sCJD is often confused with the human form of BSE. This confusion usually stems from similarities in terminology for the different illnesses, as variant CJD (vCJD) is acquired from exposure to the BSE agent. Variant CJD will be discussed in further detail in the vCJD section of the resource.

Because of this confusion, throughout the resource, the term “classic CJD” or “CJD” with no qualifying adjective will be used to refer to any of the several categories of CJD that are not vCJD. The term “classic CJD” was originally used to describe the most common subtype of sCJD (M/M 1; M/V 1), but for the purpose of this resource, it is defined to include all types of CJD other than vCJD.

The three major categories of CJD include:

  • Sporadic CJD (sCJD): the disease appears even though the person has no known environmental source for the disease. This is by far the most common type of CJD and accounts for about 85 percent of cases.1 sCJD also is known as spontaneous CJD because based on an increasingly accepted hypothesis, it is thought to arise when a person’s normal prion protein (PrPc) changes conformation spontaneously to an abnormal form (PrPSc) called a prion. The change may be facilitated by a preceding somatic mutation of the prion protein.2 There are at least six subtypes of sCJD, each with distinctive features (see Figure 5).
  • Hereditary or familial CJD: the person has a genetic mutation associated with CJD. This mutation can be confirmed by genetic tests or its presence may be inferred from a positive family history for the disease. Between 5 percent and 15 percent of CJD cases in the United States are hereditary.3
  • Acquired CJD: the disease is acquired from a known environmental source. The classic forms of CJD have been acquired iatrogenically through inadvertent exposures during medical or surgical procedures to tissues closely linked to the brains of other classic CJD cases. The sources of infection for most of these cases include cadaveric pituitary-derived hormones, dura matter grafts and contaminated neurosurgical equipment.4 No evidence exists that CJD is contagious through casual contact with a CJD patient. Since CJD was first described in 1920, fewer than 1 percent of cases have been acquired.1

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