UCSF Memory and Aging Center - Types of Prion Disease - 2012-11-09.pdf

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Types of Prion DiseaseThere are three different subtypes of prion disease categorized by how the disease is contracted.

All differ slightly with regards to typical signs, symptoms and duration of illness. The subtypes are:

Sporadic

Genetic

Acquired

poradic

poradic Creutzfeldt-Jakob Disease (sCJD)

The cause of "classic" or "sporadic" CJD is unknown, which means it occurs in people without any

known risk factors or gene mutations. Typical symptoms include imbalance and incoordination,

memory loss and impaired thinking, and psychiatric symptoms such as anxiety or depression.

Once the symptoms do appear, CJD progresses very quickly and is usually fatal within a few

months of symptom onset. sCJD typically affects people in their 60s and is rarely seen in people

younger than 40 years old. Sporadic CJD is the most common form.

poradic Fatal Insomnia (sFI)

Like sCJD, sFI is caused by a misfolded protein, but also like sCJD, what causes that protein to

misfold is unknown. Symptoms include difficulty falling asleep (insomnia), difficulty walking, weight

loss and excessive tears in the eye. The symptoms rapidly progress to loss of consciousness and

death.

enetic

amilial Creutzfeldt-Jakob Disease (fCJD)

Inherited mutations in the prion protein gene (PRNP ) cause the familial form of prion disease. This

prion gene provides instructions to your cells regarding how to make the prion protein. In fCJD, the

mutations in this gene cause the cells to produce an abnormal form of the prion protein instead ofthe normal form. In most cases, the patient with fCJD inherits the altered gene from one affected

parent. In some people, a new mutation in the gene causes fCJD. Although such people most likely

do not have an affected parent, they can pass the genetic change to their children. The symptoms

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depend on type of mutation, but they often look like classic CJD: balance and coordination

problems, memory loss and impaired thinking. Typically these symptoms appear earlier in fCJD

than in sCJD. The duration of the illness is usually longer than in the sporadic form. The genetically

inherited subtype accounts for about 15% of CJD cases.

erstmann-Sträussler-Scheinker Syndrome (GSS)

Gerstmann-Straussler-Scheinker disease (GSS) is an extremely rare, neurodegenerative brain

disorder. It is almost always inherited and is found in only a few families around the world. Onset of

the disease usually occurs between the ages of 35 and 55. In the early stages, patients may

experience varying levels of ataxia (lack of muscle coordination), including clumsiness,

unsteadiness, and difficulty walking. As the disease progresses, the ataxia becomes more

pronounced and most patients develop dementia. Other symptoms may include dysarthria (slurring

of speech), nystagmus (involuntary movements of the eyes), spasticity (rigid muscle tone), andvisual disturbances, sometimes leading to blindness. Deafness also can occur. In some families,

parkinsonian features are present. GSS belongs to a family of human and animal diseases known

as the transmissible spongiform encephalopathies (TSEs). Other TSEs include Creutzfeldt-Jakob

disease, kuru, and fatal familial insomnia. Gerstmann-Sträussler-Scheinker syndrome (GSS) is a

very rare, usually familial, fatal neurodegenerative disease that affects patients from 20 to 60 years

in age. This extremely rare disease is classified as a transmissible spongiform encephalopathy

(TSE). A rare familial form of progressive dementia inherited in an autosomal dominant manner

due to a mutant prion gene on chromosome 20pter-p12.

atal Familial Insomnia (FFI)

Fatal familial insomnia (FFI) is a very rare autosomal dominant inherited disease of the brain. The

dominant gene responsible has been found in just 28 families worldwide; if only one parent has the

gene, the offspring have a 50% chance of inheriting it and developing the disease. The disease's

genesis and the patient's progression into complete sleeplessness is untreatable, and ultimately

fatal. There are four stages of the disease before an individual's life ends. The first stage is

progressive insomnia, the trade mark of fatal familial insomnia. The first stage develops over

approximately four months and includes a collection of psychiatric problems such as panic attacks

and bizarre phobias. The second stage includes hallucinations, panic, agitation and sweating and

lasts about five months. The third stage lasts about three months and is total insomnia with weight

loss. The individual at this point looks much older and may experience incontinence. The fourth

stage is around six months long and is recognized as dementia, total insomnia and sudden death

after becoming mute.



cquired

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:

trogenic 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.

ariant 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.

uru

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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UCSF Memory and Aging Center - Types of Prion Disease - 2012-11-09.pdf