Acquired

CJD acquired by exposure to the abnormal prion protein accounts for less than 1% of known CJD cases. It is important to realize that CJD caused by exposure to the prion is extremely rare. There are three subtypes of this form:

Iatrogenic Creutzfeldt-Jakob disease (iCJD)

"Iatrogenic" literally means "physician-induced". Therefore, an iatrogenic disease is one associated with a medical practitioner or treatment. The signs and symptoms often look like classic CJD. The age at onset depends on the age at exposure and incubation time. The number of new cases of iCJD has fallen dramatically since practices changed to prevent contamination.

Cases of CJD have been linked to treatments using growth hormone prepared from human pituitary glands. Fortunately, a synthetic version of human growth hormone was developed in the 1980s, so growth hormone is now created in the laboratory rather than collected from people.

A few CJD cases have been linked to infected tissue transplants and grafts from donors who turned out to have CJD. There are no known instances where a sporadic or familial form of CJD has been passed to others through blood transfusions. Several cases of the type of CJD associated with eating infected beef have been passed through blood transfusions (see description below). Organ, tissue, and blood donors are now screened for CJD risk factors and not allowed to donate if they could potentially pass on abnormal prions to a recipient.

There have also been a few cases linked to contaminated instruments used in brain surgery. Because typical sterilization procedures do not eradicate abnormal prions, current recommendations are to destroy instruments that have been used on a patient with CJD or suspected CJD.

Variant Creutzfeldt-Jakob disease (vCJD)

This form has been linked to eating beef contaminated with Bovine Spongiform Encephalopathy (BSE or "mad cow disease") in cattle. In the early stages patients often present with personality changes and psychiatric symptoms such as depression or withdrawal. Psychiatric symptoms are often the most prominent feature early in vCJD, but dementia develops later. The motor symptoms of vCJD (stumbling, falls and difficulty walking) also tend to appear earlier in vCJD than in classic CJD. The estimated incubation period is 5 to 40 years, and the duration of illness is typically 12-14 months after signs and symptoms appear. vCJD affects people in their 20s, much earlier in age than people with sporadic CJD. One person with variant CJD has been identified in the United States and one in Canada, however, both lived in the UK during the BSE epidemic and contracted their illness from exposure in the UK.

Kuru

In the 1950s-1960s, kuru reached epidemic proportions in the South Fore tribe of Papua New Guinea. Although researchers do not know how it started, they know it spread when tribal members ritualistically consumed the tissue of affected people during funeral rites. Kuru is characterized by walking problems, shaking of the limbs, slurred speech and mood changes, but little or no dementia. It is usually fatal within 6 to 12 months. Kuru disappeared with the end of cannibalistic practices in New Guinea.

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