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Creutzfeldt-Jakob Disease (CJD)

Medically reviewed by Last updated on Aug 14, 2023.

What is Creutzfeldt-Jakob Disease (CJD)?

Harvard Health Publishing

Creutzfeldt-Jakob disease (CJD) is a rare, fatal brain disorder caused by prions. Prions are normal proteins that have changed their shape. Healthy proteins have a healthy shape, which allows them to function normally.  The misshapen prion protein causes disease by making other proteins nearby change their healthy shape to the prion's unhealthy shape.  In this way one prion makes many more prions: it slowly turns healthy proteins into prions, too.   

When symptoms eventually appear, CJD causes rapidly progressive dementia (mental decline) and involuntary jerking muscle movements called myoclonus. About 90% of people with CJD die within 1 year of diagnosis. 

About 85-95% of cases of CJD are from sporadic mutations. The DNA that makes the prion protein is changed by the mutation. The slightly different DNA makes a slightly different protein that has an abnormal shape. Less often, the mutation is hereditary (passed down from parent to child). Jewish people born in Czechoslovakia, Chile and Libya have a higher-than-average risk of CJD from this inherited mutation. Inherited CJD does not cause symptoms until adulthood. 

Prions also can be passed from an animal to a person, or from one person to another.  Fortunately, it is hard to catch prion diseases.  A type of CJD called "variant CJD" shows somewhat slower progression of brain injury and more psychiatric symptoms, and it tends to affect younger people. This type of CJD has been linked to eating beef from cattle with bovine spongiform encephalopathy (BSE), also called "mad cow disease."  BSE is caused by prions. 

In the 1990's, a small outbreak of variant CJD was described in the United Kingdom. It was caused by people eating beef infected with prions. Since then, changes in beef farming and processing practices have helped to limit the number of new cases.  

It is extremely uncommon for CJD to spread from one person to another. However, in very rare cases CJD has been transmitted by a blood transfusion, by a medical procedure (because of contaminated equipment), by contaminated tissue (such as corneas that are used for transplant) or by injections of hormones extracted from human tissues. 


CJD does not cause any symptoms at first. The first symptoms include slow thinking, difficulty concentrating, impaired judgment and memory loss.  These symptoms also occur with other diseases, such as Alzheimer's disease, so CJD can be hard to diagnose, at first. 

Soon, however, begins a severe, progressive dementia. People neglect themselves, become apathetic or irritable, and start having strong muscle spasms. Then people become completely bedridden, and eventually lapse into coma. Comatose patients may die as a result of infection associated with being immobile, such as pneumonia.


The only sure way to diagnose CJD is with a brain biopsy, an invasive test.  A less invasive test, a spinal tap (or lumbar puncture) can reveal abnormal proteins in the spinal fluid. Detection of these proteins can help make the diagnosis, but the diagnosis is made primarily by the symptoms and the doctor's examination of the nervous system. 

Other non-invasive tests can be very helpful, however:

  • Computed tomography (CT) and magnetic resonance imaging (MRI) scans may be done to look for atrophied (shrunken) brain tissue. 

  • Electroencephalogram (EEG), or brain wave, studies reveal a characteristic abnormality in 75% to 95% of people. 

  • Magnetic resonance imaging (MRI) scans also can provide helpful information. 

Usually a person's symptoms plus the results of non-invasive tests make the diagnosis clear.  Brain biopsy is done only if there is a possibility the patient may have another disorder that could be treated.

Expected Duration

Ninety percent to 95% of people with CJD die within 3 to 12 months after symptoms start. A few people with the disease survive more than 2 years. 


Most cases of CJD cannot be prevented, but the disease fortunately is rare: only one person in one million develops the disease each year. 

Cases of CJD caused by medical procedures, or by eating infected animal meat, are even more rare. But they are preventable. Health care professionals minimize the risk by handling the fluids and tissues of patients with CJD with extreme caution, and by using special sterilization methods to disinfect equipment. Likewise, new precautions have been taken by the beef farming and beef processing industry. These precautions have helped to make the risk of infection from eating beef exceedingly small.  

Blood banks have put additional restrictions on blood donors. Blood banks in the United States now turn away blood donations from people who have lived in the United Kingdom for three months or longer from 1980 through 1996. 


CJD cannot be cured, but some of the symptoms can be treated. Narcotics may be used to relieve pain, and anticonvulsant drugs, such as clonazepam (Klonopin) and valproic acid (Depacon, Depakene, Depakote), may be used for muscle spasms. Research studies are looking into other drugs that may be helpful.

When To Call A Professional

Seek medical help for signs of dementia such as sudden or gradual changes in memory, thinking skills, mood or behavior and for alterations in vision or movement ability.


The disease is fatal, with the majority of deaths occurring within 3 to 12 months of illness.

Additional Info

National Institute of Neurological Disorders and Stroke
National Institutes of Health

Creutzfeldt-Jakob Disease Foundation, Inc.

Centers for Disease Control and Prevention (CDCP)

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.