Classic CJD (Creutzfeldt-Jakob Disease)

Classic CJD is a human prion disease. It is a neurodegenerative disorder with characteristic clinical and diagnostic features. This disease is rapidly progressive and always fatal. Infection with this disease leads to death usually within 1 year of onset of illness.

Important Note: Classic CJD is not related to "mad cow" disease. Classic CJD also is distinct from "variant CJD", another prion disease that is related to BSE.

For information about these diseases, see:

Occurrence and Transmission

Classic CJD has been recognised since the early 1920s. The most common form of classic CJD is believed to occur sporadically, caused by the spontaneous transformation of normal prion proteins into abnormal prions. This sporadic disease occurs worldwide, including the United States, at a rate of approximately one case per 1 million population per year, although rates of up to two cases per million are not unusual. The risk of CJD increases with age, and in persons aged over 50 years of age, the annual rate is approximately 3.4 cases per million. In recent years, the United States has reported fewer than 300 cases of CJD a year.

Whereas the majority of cases of CJD (about 85%) occur as sporadic disease, a smaller proportion of patients (5-15%) develop CJD because of inherited mutations of the prion protein gene. These inherited forms include Gerstmann-Straussler-Scheinker syndrome and fatal familial insomnia.

Clinical and Pathologic Characteristics of Classic CJD

Classic CJD characteristics, as compared to variant CJD, are presented in the table below.

Clinical and Pathologic Characteristics Distinguishing Classic CJD from Variant CJD
Characteristic Classic CJD Variant CJD
Median age at death 68 years 28 years
Median duration of illness 4-5 months 13-14 months
Clinical signs and symptoms Dementia; early neurologic signs Prominent psychiatric/behavioural symptoms; painful dyesthesiasis; delayed neurologic signs
Periodic sharp waves on electroencephalogram Often present Often absent
"Pulvinar sign" on MRI
  		•  Not reported Present in >75% of cases
    Presence of "florid plaques" on neuropathology Rare or absent Present in large numbers
    Immunohitochemical analysis of brain tissue Variable accumulation Marked accumulation of protease-resistance prion protein
    Presence of agent in lymphoid tissue Not readily detected Readily detected
    Increased glycoform ratio on immunoblot analysis of protease-resistance prion protein Not reported Marked accumulation of protease-resistance prion protein
    Source: Adapted from Belay E., Schonberger L. Variant Creutzfeldt-Jakob Disease and Bovine Spongiform Encephalopathy. Clin Lab Med 2002;22:849-62.
  • An abnormal signal in the posterior thalami on T2- and diffusion-weighted images and fluid-attenuated inversion recovery sequences on brain magnetic resonance imaging (MRI); in the appropriate clinical context, this signal is highly specific for vCJD.
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