From MayoClinic.com

Creutzfeldt-Jakob disease (CJD) is a rare, degenerative, invariably fatal brain disorder. Worldwide, doctors typically diagnose one case per million people each year, most commonly in older adults.

That changed a decade ago when an unusually large number of people in Great Britain developed what appeared to be CJD. The outbreak was alarming not only because so many people died of a presumably rare disease, but also because of their relatively young ages - the youngest victim was just 19. Even more disturbing was the way they appeared to have contracted the disease. All had eaten meat from cattle suspected of having bovine spongiform encephalopathy (BSE), the medical term for mad cow disease.

Scientists eventually concluded that the new ailment - named variant CJD (vCJD) - was a form of Creutzfeldt-Jakob disease resulting from exposure to BSE. Since then, a growing number of cases of vCJD have been linked to contaminated beef in Great Britain and in other countries, including Spain, Portugal, France and Germany. The risk, however, appears to be extremely low.

Although "classic" CJD doesn't appear to be connected to mad cow disease, it's similar to vCJD in many respects. Both are thought to occur when misshapen brain proteins (prions) attack brain cells, creating sponge-like holes in brain tissue. Both cause profound mental and physical deterioration, and both appear to have long incubation periods before signs and symptoms appear.

Once a person becomes sick, the course of the disease is swift. People usually die from complications of CJD just months after developing symptoms, and from vCJD within a year or so. No treatment exists for either type of CJD, and nothing slows the progression of the disease.

Signs and symptoms

A number of subtypes of CJD exist, many with slight variations in signs and symptoms. Yet the various forms of the disease are far more alike than they are different, and everyone affected by CJD must eventually contend with grave mental and physical problems.

Although classic CJD and variant CJD share the characteristics listed below, the characteristics manifest somewhat different in each form of the disease.

Long incubation period
The incubation period is the time it takes you to become sick after you've contracted a disease. Cold symptoms usually start a day or two after you're exposed to a cold virus, for example, whereas the timeframe for CJD is considerably longer.

• Classic CJD. It often takes years or even decades after infection before someone with classic CJD develops signs and symptoms of the disease.

• Variant CJD. Although it's too early to know for certain, scientists suspect that the same is true of vCJD. That's why some experts predict that an epidemic of vCJD is still to come.

Personality changes
Both classic and variant CJD begin with personality changes such as anxiety, depression, memory loss and impaired thinking. As the diseases progress, mental symptoms become more severe.

• Anxiety

• Cold

• Depression

• Heart failure

Ultimately, people with both forms of CJD develop dementia — a mental disorder that robs them of the ability to speak, think, reason, remember and move. Although the symptoms of CDJ sometimes resemble those of other neurologic disorders such as Alzheimer's and Huntington's disease, CDJ usually progresses much more rapidly than other diseases associated with dementia.

• Classic CJD. The progression from initial personality changes to complete dementia occurs quickly — usually within six months or less of the onset of symptoms.

• Variant CJD. Psychiatric symptoms are the most prominent feature early in vCJD, but dementia develops later in the course of the disease than it does in classic CJD.

Problems with balance and coordination
Both types of CJD affect balance and coordination, leading to stumbling, falls and difficulty walking, but these problems occur sooner in vCJD than they do in classic CJD.

Coma and death
Most people lapse into coma before succumbing to these invariably fatal diseases.

• Classic CJD. People with classic CJD generally live an average of only 7 months after signs and symptoms appear, although some people may live as long as one or two years after the onset of symptoms. Death is usually not a result of the disease itself, but rather of complications such as heart failure, respiratory failure and pneumonia.

• Variant CJD. People with vCJD tend to live slightly longer — about 12 to 14 months after signs and symptoms appear.

Other signs and symptoms of classic CJD include:

• Blurred vision and, often, eventual blindness

• Involuntary muscle contractions (myoclonus)

• Difficulty speaking, which may lead to mumbling or speech that's difficult to understand

• Difficulty swallowing

Additional signs and symptoms of vCJD include:

• A sense that the skin feels sticky

• Sensations of cold or pain

• Muscle paralysis

• Tremors

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