Creutzfeldt-Jakob disease
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What is Creutzfeldt-Jakob disease?
Creutzfeldt-Jakob disease (CJD) is a rare and fatal degenerative disease of the central nervous system that occurs worldwide in about one in every one million people.
CJD is caused by prions, which are abnormal forms of a normal protein in the brain. As prions replicate, they convert normal proteins into their abnormal shape, accumulating within nerve cells and causing neurodegeneration. The disease results in a characteristic spongelike pattern of neuronal destruction, leaving brain tissue filled with holes. Diagnosis is typically confirmed through brain biopsy.
CJD is characterized by progressive dementia, abnormal vision, and involuntary movements. The disease is usually fatal within a year of the onset of symptoms.
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What part of the body does Creutzfeldt-Jakob disease affect?
Creutzfeldt-Jakob disease (CJD) is a rare, fatal, degenerative disease that affects the central nervous system, specifically the brain. It is caused by prions, which are abnormal proteins that accumulate and destroy neurons, leading to a characteristic spongelike pattern in the brain tissue. This destruction results in a progressive loss of muscular coordination and premature dementia.
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What happens to the brain during Creutzfeldt-Jakob disease?
In Creutzfeldt-Jakob disease (CJD), prions, which are abnormal proteins, accumulate in nerve cells, causing neurodegeneration. This leads to a characteristic spongelike pattern of neuronal destruction, filling brain tissue with holes. As prions multiply, converting normal proteins into their abnormal shape, they resist breakdown and accumulate within neurons, destroying them. This progressive neuron destruction results in the brain becoming filled with holes, displaying a spongiform pattern.
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What are prions, and how do they cause damage in Creutzfeldt-Jakob disease?
Prions are abnormal, misfolded forms of a normally harmless protein found in the brain. In Creutzfeldt-Jakob disease (CJD), these prions trigger a chain reaction, causing normal prion proteins to misfold and become infectious.
This leads to a buildup of prion proteins that resist breakdown by cellular enzymes. As prions accumulate within neurons, they destroy them, leading to the development of porous, spongelike holes in brain tissue. This progressive neuron destruction results in the fatal degeneration of the central nervous system characteristic of CJD.
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What are some typical signs or changes found in the brain of someone with Creutzfeldt-Jakob disease?
Creutzfeldt-Jakob disease (CJD) is a rare, fatal, degenerative disease of the central nervous system. CJD, as well as other spongiform encephalopathies, is caused by a prion, an unusual pathogenic agent. Prions replicate by converting normal proteins into abnormal shapes, accumulating within nerve cells and causing neurodegeneration.
Progressive neuron destruction eventually causes brain tissue to become filled with holes in a spongelike pattern. The onset of CJD is usually characterized by vague psychiatric or behavioral changes, followed by progressive dementia, abnormal vision, and involuntary movements. The disease is usually fatal within a year of symptom onset.
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How does Creutzfeldt-Jakob disease differ from other brain diseases in terms of pathology?
Creutzfeldt-Jakob disease (CJD) is a rare, fatal, degenerative central nervous system disorder that occurs worldwide in about one in every one million people. CJD, kuru, and scrapie are types of transmissible spongiform encephalopathies with a characteristic spongelike pattern of neuronal destruction that leaves brain tissue filled with holes.
CJD is caused by prions, which are abnormal forms of a normal protein in the brain. Prions replicate by converting normal proteins into their abnormal shape, accumulating within nerve cells and causing neurodegeneration. Diagnosis is typically confirmed through brain biopsy.
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Creutzfeldt-Jakob disease (CJD), rare fatal degenerative disease of the central nervous system. CJD occurs throughout the world at an incidence of one in every one million people. Among certain populations, such as Libyan Jews, rates are somewhat higher.
The disease was first described in the 1920s by the German neurologists Hans Gerhard Creutzfeldt and Alfons Maria Jakob. CJD is similar to other neurodegenerative diseases such as kuru, a human disorder, and scrapie, which occurs in sheep and goats. All three diseases are types of transmissible spongiform encephalopathies, so called because of the characteristic spongelike pattern of neuronal destruction that leaves brain tissue filled with holes.
Causes and symptoms
CJD, as well as other spongiform encephalopathies, is caused by an unusual pathogenic agent called a prion. A prion is a deviant form of a normally harmless protein found in the brains of mammals and birds. As prions replicateāby converting normal forms of the protein into their abnormal shapeāthey accumulate within nerve cells, causing neurodegeneration.
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CJD commonly occurs in adults between ages 40 and 70, although some young adults have been stricken with the disease. Both men and women are affected equally. The onset of the disease is usually characterized by vague psychiatric or behavioral changes, which are followed within weeks or months by a progressive dementia that is often accompanied by abnormal vision and involuntary movements. The disease is usually fatal within a year of symptom onset.
Types
There are three major types of CJD: familial (fCJD), sporadic (sCJD), and acquired (aCJD). Both sCJD and aCJD may be further divided into subtypes. The most common sCJD subtype is sCJDMM1. Subtypes of aCJD include iatrogenic (iCJD) and variant (vCJD) forms of the disease (kuru is sometimes considered a third subtype of aCJD).
Acquired CJD, which occurs through infection with the prion protein, accounts for only 1 percent of all CJD cases. Sporadic (i.e., occurring at random) forms account for the majority of casesāat least 85 percent. In these cases it is unclear what molecular process causes the prion protein to appear in the first place. The protein may arise from a mutation incurred as the body ages or as a result of a spontaneous conversion in the proteinās shape.
Between 5 and 15 percent of CJD cases show a familial pattern of inheritance. In these inherited cases a mutation in a gene designated PRNP), which encodes the prion protein PrP, is passed from parent to child in a dominant fashion (i.e., only one of the two copies of the gene that are inheritedāone from each parentāneed be mutated for disease to occur). More than 50 different mutations in PRNP have been identified. While some of these mutations cause CJD, others cause Gerstmann-StrƤussler-Scheinker syndrome and fatal familial insomnia. In addition, mutations have been identified that do not cause disease but may render individuals more susceptible to infection with the prion. These latter mutations may be involved in some of the sporadic incidences of the disease.
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Transmission
There is no evidence that a person with CJD is contagious. The rare cases of the disease that arise from human-to-human transmission are considered forms of iCJD (essentially physician-induced CJD), having been caused by exposure to the prion during medical procedures. Such accidental transmission has occurred in corneal transplants, through the use of contaminated medical or surgical instruments, and through the transfusion of contaminated blood products, including prion-infected plasma. Transmission also may have occurred through the injection of growth hormone derived from human pituitary glands.
Although human-to-animal prion transmission has been demonstrated in the laboratory, researchers are not sure whether prions that cause disease in one species can give rise to a prion disease in humans. Concern about this type of transmission increased in the mid-1990s when a number of young adults in Great Britain developed a new variant form of CJD (vCJD, or nvCJD). There is increasing evidence that these cases resulted from the consumption of tissues (notably nerve tissue) contaminated with the prion that causes bovine spongiform encephalopathy (BSE), or mad cow disease.
Chronic wasting disease, which is caused by a prion that occurs in elk and deer, is similar in nature to BSE. Although there have been no cases of animal-to-human transmission of this prion, researchers suspect that eating contaminated tissues of deer and elk could give rise to another variant form of CJD. As a result, scientists have been monitoring cases of CJD in areas where chronic wasting disease is endemic.
Diagnosis and treatment
Diagnosis of CJD typically entails spinal tap, electroencephalography, and other procedures to assess neurological function in order to rule out conditions that might produce similar symptoms. Diagnosis is confirmed through brain biopsy, in which a small section of tissue is removed from the brain and examined in a laboratory.
Scientists are developing tests capable of detecting prions in cerebrospinal fluid and blood. Such tests could enable early diagnosis and improve prion screening for blood transfusions.
There is no known cure for CJD, nor can the progression of the disease be delayed by medication or surgery. Hence, treatment is supportive, being aimed primarily at minimizing pain and discomfort.