Creutzfeldt-Jakob disease (subacute spongiform encephalopathy) is a prion disease characterized by progressive deterioration of mental function, leading to dementia, involuntary jerking of muscles (myoclonus), and staggering when walking. A variant form is acquired by eating contaminated beef.
Creutzfeldt-Jakob disease (CJD) is a prion disease (see see Overview of Prion Diseases), which develops when a normal protein called cellular prion protein (PrPC) changes into disease-causing prion. Prions usually cause tiny bubbles to form in brain cells, which gradually die. When enough brain cells die, symptoms develop, followed eventually by the person's death.
CJD may occur spontaneously (called sporadic CJD), occur in families (called familial CJD), or be acquired.
Sporadic CJD, the most common form, affects about 1 in a million people each year throughout the world. It usually affects people over 40 years old, usually around age 60. For this form, no cause is known.
Familial CJD results from a mutation in the gene for PrP, which causes normal PrPC to change shape (misfold) and become disease-causing prion. Familial CJD is often inherited and usually starts at an earlier age and lasts longer than sporadic CJD.
CJD can be acquired by eating beef or beef products from cattle who have bovine spongiform encephalopathy (mad cow disease). This type of CJD is called variant CJD. Variant CJD usually begins around age 30 or younger, in contrast to sporadic CJD, which usually begins around age 60. As of 2011, 176 cases of variant CJD have occurred in the United Kingdom, and 49 additional cases have occurred elsewhere. Spread of the disease has been controlled by massive slaughter of cattle and changes in how beef is processed in the United Kingdom. Widespread surveillance for the disease in cattle has resulted in a progressively lower number of new cases in the United Kingdom. No case occurred in 2012. Although no reported case of variant CJD has originated in North America, mad cow disease has been reported in a few North American cattle (4 in the United States and 19 in Canada).
CJD can also be acquired during a medical procedure (called iatrogenic CJD)—for example, when a cornea or possibly other tissues from affected donors are transplanted or when brain surgery is done with instruments previously used to operate on a person who had CJD. Routine cleansing and sterilization procedures do not destroy prions. However, bleach is effective. Acquiring the disease during a medical procedure is extremely unlikely.
CJD has been acquired when hormones derived from human pituitary glands were used for treatment. For example, the disease developed in some children who were treated with growth hormone derived from pituitary glands of cadavers that contained prions. These hormones are now genetically engineered rather than prepared from cadavers, so there is no longer a risk of CJD.
Four cases of CJD have been transmitted through blood transfusion. In all cases, the disease was acquired from donors affected by the variant form. The last case was reported in 1999.
CJD has never been reported to be transmitted through casual or even intimate contact with people who have the disease.
The most common early symptoms—memory loss and confusion—may resemble those of other dementias, such as Alzheimer disease. These symptoms are the first to occur in about 70% of people with CJD but eventually develop in all affected people. For about 15 to 20% of people, the first symptom is loss of muscle coordination. In people with variant CJD, the first symptoms tend to be psychiatric symptoms (such as anxiety or depression), rather than memory loss. Later symptoms are similar in both forms.
Whether symptoms develop gradually or abruptly, mental function continues to deteriorate, often causing such symptoms as neglect of personal hygiene, listlessness, and irritability. Some people tire easily and become sleepy. Others cannot fall asleep.
Muscles usually begin to jerk involuntarily and quickly during the first 6 months after symptoms begin. Muscles may tremble, and people may become clumsy and uncoordinated. Walking becomes unsteady, resulting in staggering (similar to the walk of a person who is drunk). Movements may be slow. Impairment of muscle control may result in unusual postures, such as twisting of the trunk or limbs forward and sideways. Muscles may jerk when stretched. Some people have hallucinations and seizures.
People may startle easily, and the resulting responses, such as jumping when a loud noise is heard, are exaggerated. Startling may trigger muscle jerking. The muscles that control breathing and coughing are usually impaired, increasing the risk of pneumonia. Vision may become blurry or dim.
The symptoms worsen, usually much more rapidly than in Alzheimer disease, resulting in severe dementia.
Most people with CJD die within 6 to 12 months after symptoms appear. About 10 to 20% of people survive for 2 years or more. People with variant CJD usually survive for 1 1/2 years. Often, the cause of death is pneumonia.
People may have no symptoms for months or years after they acquire variant CJD. If variant CJD was acquired by eating contaminated beef, symptoms usually begin 6 to 12 years later.
Doctors consider CJD in older people when mental function is deteriorating quickly, when muscles jerk involuntarily, when their walk is unsteady and staggering, and when other dementias have been ruled out by routine testing. Doctors may suspect variant CJD in people who have typical symptoms and who have eaten processed beef in the United Kingdom or in other countries where mad cow disease has occurred. They may suspect familial CJD when younger people have relatives with CJD.
Diagnosis may be difficult. The most useful test is magnetic resonance imaging (MRI). It can detect characteristic changes in the brain, including some that occur only in people with variant CJD. A spinal tap may be done to obtain a sample of cerebrospinal fluid, which is tested for protein 14-3-3 and other unusual proteins. These proteins are often (but not always) present in people with CJD, and they may be present in many other disorders. Thus, this test can support the diagnosis but cannot confirm or exclude it. A new test that can detect prion in the cerebrospinal fluid is being developed.
EEG is usually done to check for characteristic abnormalities in the electrical activity of the brain, which occur in 70% of people with CJD. However, these changes occur late in the disease and may not be present all the time.
Usually, a sample of brain tissue is examined under a microscope (biopsied) to check for evidence of other disorders that could be causing the symptoms, particularly ones that can be treated.
Currently, CJD cannot be cured, and its progress cannot be slowed. The disease is fatal, usually within months or a few years. However, certain drugs may be given to relieve symptoms. For example, the anticonvulsant valproate and the antianxiety drug clonazepam may reduce muscle jerking. Sedative or antipsychotic drugs can sometimes help calm people who are anxious.
General support and care for the person and family members are important. Day care centers and respite and long-term care may be useful. The CJD Foundation provides support and information (see Creutzfeldt-Jakob Disease Foundation).
Last full review/revision May 2013 by Pierluigi Gambetti, MD