Creutzfeldt-Jakob disease

Creutzfeldt-Jakob Disease (CJD) is a very rare and incurable brain disease that is ultimately fatal. It is the most common of the transmissible spongiform encephalopathies (TSEs). It is a progressive neurological disorder which belongs to a group of degenerative neurologic diseases known as subacute spongiform encephalopathies. more...

Causes

TSEs (also known as prion diseases) are caused by a unique type of infectious agent called prions, an abnormally-structured form of a protein found in the brain. Other prion diseases include Gerstmann-Sträussler-Scheinker syndrome (GSS), fatal familial insomnia (FFI) and kuru in humans, as well as BSE and scrapie in animals.

The prion that is believed to cause Creutzfeldt-Jakob exhibits at least two stable conformations. One, the native state, is water soluble and present in healthy cells. As of 2006, its biological function is unknown. The other conformational state is very poorly water-soluble and readily forms protein aggregates.

The CJD prion is dangerous because it promotes refolding of native proteins into the diseased state. The number of misfolded protein molecules will increase exponentially and the process leads to a large quantity of insoluble prions in affected cells. This mass of insoluble proteins disrupts cell function and causes cell death. Once the prion is transmitted, the defective proteins invade the brain and get produced in a self-sustaining feedback loop, causing exponential spread of the prion, and the patient dies within a few months; a few patients live as long as two years.

Incidence and prevalence

Although CJD is the most common human prion disease, it is still extremely rare and only occurs in about one out of every one million people. It usually affects people aged 45–75, most commonly appearing in people between the ages of 60–65. The exception to this is the more recently-recognised 'variant' CJD (vCJD), which occurs in younger people.

CDC monitors the occurrence of CJD in the United States through periodic reviews of national mortality data: According to the CDC:

• CJD occurs worldwide at a rate of about 1 case per million population per year.
• On the basis of mortality surveillance from 1979 to 1994, the annual incidence of CJD remained stable at approximately 1 case per million persons in the United States.
• In the United States, CJD deaths among persons younger than 30 years of age are extremely rare (fewer than 5 deaths per billion per year).
• The disease is found most frequently in patients 55–65 years of age, but cases can occur in persons older than 90 years and younger than 55 years of age.
• In more than 85 percent of cases, the duration of CJD is less than 1 year (median: 4 months) after onset of symptoms.

Symptoms

The first symptom of CJD is rapidly progressive dementia, leading to memory loss, personality changes and hallucinations. This is accompanied by physical problems such as speech impairment, jerky movements (myoclonus), balance and coordination dysfunction (ataxia), changes in gait, rigid posture, and seizures. The duration of the disease varies greatly, but sporadic (non-inherited) CJD can be fatal within months or even weeks (Johnson, 1998). In most patients, these symptoms are followed by involuntary movements and the appearance of a typical diagnostic electroencephalogram tracing.

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