Creutzfeldt-Jakob disease

Creutzfeldt-Jakob disease (CJD) is a rare fatal brain disorder that usually occurs later in life and runs a rapid course. In the early stages of the disease, patients may have failing memory, behavior changes, impaired coordination, and vision problems. As CJD progresses, mental deterioration becomes severe, and they can have uncontrolled movements, blindness, weakness, and go into a coma. This condition often leads to death within a few weeks or months after symptoms begin. About 90 percent of patients do not survive for more than one year. In the United States, about 300 people are diagnosed with this condition each year. It occurs in approximately one in every one million people worldwide.

CJD can be very difficult to diagnose because it is similar to other forms of dementia. The only way to confirm the diagnosis is to test a small sample of brain tissue, which can be done by brain biopsy or autopsy. CJD is caused by the build up of abnormal prion proteins in the brain. For most patients, the reason for the abnormal prions is unknown (sporadic CJD). About 5 to 10 percent of cases are due to an inherited genetic mutation associated with CJD (familial CJD). This condition can also be acquired through contact with infected brain tissue (iatrogenic CJD) or consuming infected beef (variant CJD). There is no specific treatment for CJD, so the goal is to make a person as comfortable as possible.^[1][2]

There are three major categories of Creutzfeldt-Jakob disease (CJD):^[1]

• In sporadic CJD, the disease appears even though the person has no known risk factors for the disease. This is by far the most common type of CJD and accounts for at least 85 percent of cases.
• In hereditary CJD, the person has a family history of the disease and/or tests positive for a genetic mutation associated with CJD. About 5 to 10 percent of cases of CJD in the United States are hereditary.
• In acquired CJD, the disease is transmitted by exposure to brain or nervous system tissue, usually through certain medical procedures. There is no evidence that CJD is contagious through casual contact with a CJD patient. Since CJD was first described in 1920, fewer than 1 percent of cases have been acquired CJD.

Creutzfeldt-Jakob disease (CJD) is characterized by rapidly progressive dementia. Initially, patients experience problems with muscular coordination; personality changes, including impaired memory, judgment, and thinking; and impaired vision. People with the disease also may experience insomnia, depression, or unusual sensations. CJD does not cause a fever or other flu-like symptoms. As the illness progresses, the patients’ mental impairment becomes severe. They often develop involuntary muscle jerks called myoclonus, and they may go blind. They eventually lose the ability to move and speak and enter a coma. Pneumonia and other infections often occur in these patients and can lead to death.^[1]

There are several known variants of CJD. These variants differ somewhat in the symptoms and course of the disease. For example, a variant form of the disease-called new variant or variant (nv-CJD, v-CJD), described in Great Britain and France-begins primarily with psychiatric symptoms, affects younger patients than other types of CJD, and has a longer than usual duration from onset of symptoms to death. Another variant, called the panencephalopathic form, occurs primarily in Japan and has a relatively long course, with symptoms often progressing for several years. Scientists are trying to learn what causes these variations in the symptoms and course of the disease.^[1]

Some researchers believe an unusual 'slow virus' or another organism causes Creutzfeldt-Jakob disease (CJD). However, they have never been able to isolate a virus or other organism in people with the disease. Furthermore, the agent that causes CJD has several characteristics that are unusual for known organisms such as viruses and bacteria. It is difficult to kill, it does not appear to contain any genetic information in the form of nucleic acids (DNA or RNA), and it usually has a long incubation period before symptoms appear. In some cases, the incubation period may be as long as 40 years. The leading scientific theory at this time maintains that CJD and the other TSEs are caused by a type of protein called a prion.^[1]

Prion proteins occur in both a normal form, which is a harmless protein found in the body’s cells, and in an infectious form, which causes disease. The harmless and infectious forms of the prion protein have the same sequence of amino acids (the 'building blocks' of proteins) but the infectious form of the protein takes a different folded shape than the normal protein. Sporadic CJD may develop because some of a person’s normal prions spontaneously change into the infectious form of the protein and then alter the prions in other cells in a chain reaction.^[1]

Once they appear, abnormal prion proteins aggregate, or clump together. Investigators think these protein aggregates may lead to the neuron loss and other brain damage seen in CJD. However, they do not know exactly how this damage occurs.^[1]

About 5 to 10 percent of all CJD cases are inherited. These cases arise from a mutation, or change, in the gene that controls formation of the normal prion protein. While prions themselves do not contain genetic information and do not require genes to reproduce themselves, infectious prions can arise if a mutation occurs in the gene for the body’s normal prion protein. If the prion protein gene is altered in a person’s sperm or egg cells, the mutation can be transmitted to the person’s offspring. Several different mutations in the prion gene have been identified. The particular mutation found in each family affects how frequently the disease appears and what symptoms are most noticeable. However, not all people with mutations in the prion protein gene develop CJD.^[1]

There is currently no single diagnostic test for Creutzfeldt-Jakob disease (CJD). When a doctor suspects CJD, the first concern is to rule out treatable forms of dementia such as encephalitis (inflammation of the brain) or chronic meningitis. A neurological examination will be performed and the doctor may seek consultation with other physicians. Standard diagnostic tests will include a spinal tap to rule out more common causes of dementia and an electroencephalogram (EEG) to record the brain’s electrical pattern, which can be particularly valuable because it shows a specific type of abnormality in CJD. Computerized tomography of the brain can help rule out the possibility that the symptoms result from other problems such as stroke or a brain tumor. Magnetic resonance imaging (MRI) brain scans also can reveal characteristic patterns of brain degeneration that can help diagnose CJD.^[1]

The only way to confirm a diagnosis of CJD is by brain biopsy or autopsy. In a brain biopsy, a neurosurgeon removes a small piece of tissue from the patient’s brain so that it can be examined by a neuropathologist. This procedure may be dangerous for the patient, and the operation does not always obtain tissue from the affected part of the brain. Because a correct diagnosis of CJD does not help the patient, a brain biopsy is discouraged unless it is needed to rule out a treatable disorder. In an autopsy, the whole brain is examined after death.^[1]

Scientists are working to develop laboratory tests for CJD. One such test, developed at the National Institute of Neurological Disorders and Stroke (NINDS) at the National Institutes of Health (NIH), studies a person's cerebrospinal fluid to see of it contains a protein marker that indicates neuronal degeneration.This can help to diagnose CJD in people who already show the clinical symptoms of the disease. This test is much easier and safer than a brain biopsy. The false positive rate is about 5 to 10 percent. Scientists are working to develop this test for use in commercial laboratories. They are also working to develop other tests for this disorder.^[1]   

There is no treatment that can cure or control Creutzfeldt-Jakob disease (CJD). Researchers have tested many drugs, including amantadine, steroids, interferon, acyclovir, antiviral agents, and antibiotics. Studies of a variety of other drugs are now in progress. However, so far none of these treatments has shown any consistent benefit in humans.^[1]

Current treatment for CJD is aimed at alleviating symptoms and making the patient as comfortable as possible. Opiate drugs can help relieve pain if it occurs, and the drugs clonazepam and sodium valproate may help relieve myoclonus. During later stages of the disease, changing the person’s position frequently can keep him or her comfortable and helps prevent bedsores. A catheter can be used to drain urine if the patient cannot control bladder function, and intravenous fluids and artificial feeding also may be used.^[1]