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May 2003

Classical Creutzfeldt-Jakob Disease

Creutzfeldt-Jakob Disease (CJD) is a rare disease that affects the central nervous system. There are two forms of CJD, classical and a new form, variant. Three types of classical CJD are recognized: sporadic, familial and iatrogenic.

  • Sporadic CJD, which comprises 85-90% of all classical CJD cases, occurs spontaneously in the general population with no known cause or triggering event.
  • Familial CJD is even rarer, accounting for 10 to 15 percent of all classical CJD cases. It occurs in individuals within specific families with a genetic predisposition.
  • Iatrogenic CJD is the rarest of all, accounting for less than 1 percent of all classical CJD cases. It occurs accidentally as the result of certain medical procedures, where there is transmission of the causative agent from a patient with the disease to another patient. So far, it has occurred only as a result of injection of certain hormones taken from the brain of cadavers (e.g. human growth hormone), through cornea or dura mater 1 grafts, and through contaminated instruments used in neurosurgery. The tissues that are most infectious include the brain, spinal cord, pituitary gland and some parts of the eye.

Classical CJD occurs in the general population at a rate of about one case per million people per year throughout the world. In Canada, about 30 cases of classical CJD are diagnosed each year.

The average age of onset of classical CJD is 60 years of age, with most cases in patients between 45 and 75. Death often occurs within 2 to 3 months, with 70 percent of patients dying in less than 6 months.

In classical CJD, the period between exposure to the infection in cases where this is known and the onset of symptoms can range from 1 to 30 years or more. Symptoms usually occur suddenly and the patient's condition rapidly declines. Early symptoms include lapses in memory, mood swings similar to depression, lack of interest and social withdrawal. The patient may become unsteady on his/her feet. Later symptoms may include blurred vision, sudden jerking movements and rigidity in the limbs. The patient may experience slurred speech and have difficult swallowing. There is progressive mental deterioration and, eventually, movement and speech are lost.

Currently, the only way to diagnose classical CJD with certainty is by microscopic examination of the brain tissue, most often through autopsy.

1 Dura mater: membrane covering the brain