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Familial Creutzfeldt-Jakob disease

Other Names: Transmissible Spongiform Encephalopathies, Prion disorder


Familial Creutzfeldt-Jakob disease is a very rare genetic condition that causes progressive degeneration of the brain. It is caused by mutations in the PRNP gene that makes the major prion protein.

Characteristics of Familial Creutzfeldt-Jakob disease
Creutzfeldt-Jakob disease (CJD) is a progressive prion disease that invariably leads to death. Prions are proteins most commonly located in the brain. In prion diseases, these prions become misfolded and spread by causing other proteins to abnormally fold. The abnormal folding of the prion proteins leads to brain damage and the common characteristics of prion diseases such as memory loss, cognitive difficulties, and uncoordinated movements (ataxia and myoclonus – sudden jerky movements).
Most cases of CJD are sporadic (random, not inherited), but about 10-15% of cases are inherited (familial). Common symptoms of CJD include memory loss, decline in thinking ability (cognitive impairment), psychiatric symptoms, uncoordinated movements, weakness, and seizures. Symptoms typically appear around 30 to 50 years of age. Once symptoms begin, the disease usually progresses quickly, leading to death within a few months to 5 years.

Diagnosis/Testing
Familial CJD is caused by changes or mutations in the PRNP gene. This gene makes the major prion protein. Mutations in the PRNP gene cause abnormal prion proteins to build up in the brain. This in turn causes healthy brain tissue to deteriorate resulting in the symptoms commonly seen in individuals with CJD. While having a mutation in the PRNP gene confirms a diagnosis of familial CJD, mutations are not found in all individuals with familial CJD.
Testing for CJD may also include an EEG study, where electrodes are attached to the scalp allowing doctors to see characteristic abnormalities in brain activity. Other brain imaging, such as a brain MRI, or spinal fluid tests might be done as well. Unfortunately, these studies cannot confirm a suspected diagnosis of CJD. The only way to confirm a diagnosis of CJD is to have a full examination of the brain during an autopsy.

Management/Surveillance
Currently, there is no cure or treatment for CJD. However, antiviral medicines, steroids, and antibiotics are being researched as possible treatment options. Most treatments focus on making the patient as comfortable as possible while trying to alleviate pain and other symptoms.

Mode of inheritance
Familial CJD is inherited in an autosomal dominant pattern. This means inheriting one PRNP mutation is enough for an individual to be affected with CJD. The mutation can be inherited from an affected parent or it can occur brand new (de novo) in an affected child.

Risk to family members
The risk to family members depends on whether or not the individual with CJD has a parent affected with CJD. If a parent also had CJD, the risk of having a child with CJD is 50% with each pregnancy. If a parent does not have CJD, the risk of other siblings being affected is very low.

Special considerations
There are other, more common, types of CJD called sporadic CJD and variant CJD. Sporadic CJD has the same features as familial CJD; however, the age of onset is typically after age 60 and the duration is shorter (about 6 months). The cause of sporadic CJD is unknown.
Variant CJD occurs by the ingestion of beef or beef products contaminated with bovine spongiform encephalopathy (BSE). BSE is the prion disease of cattle, commonly known as mad cow disease. The duration of this disease is about 1.5 years. Features of variant CJD include pain in the lower extremities, progressive dementia, and ataxia.

Resources
National Institute of Neurological Disorders and Stroke: Creutzfeldt-Jakob Disease Fact Sheet
Creutzfeldt-Jacob Disease Foundation
CJD Surveillance: National Prion Disease Pathology Surveillance Center
Genetics Home Reference: Prion disease

References
Capellari, S., et al. (2011)."Genetic Creutzfeldt-Jakob disease and fatal familial insomnia: insights into phenotypic variability and disease pathogenesis." Acta Neuropathologica 121(1): 21-37.
Knight, R. (2006)."Creutzfeldt-Jakob disease: A Rare Cause of Dementia in Elderly Persons." Critical Infectious Diseases 43(3): 340-346.
Mastrianni J. (Updated 2 January 2014). Genetic Prion Diseases. In: GeneReviews at GeneTests Medical Genetics Information Resource (database online). Copyright, University of Washington, Seattle. 1997-2013. Available at http://www.ncbi.nlm.nih.gov/books/NBK1229/. Accessed [03/06/2014].
Prusiner, SB. (2013)."Biology and Genetics of Prions Causing Neurodegeneration." Annual Review of Genetics 47: 601-623.

Created:03/2014

Updated:mm/yyyy

Created by:Corrie Bourdon, MS, CGC

Edited by:Seema Jamal, MSc, LCGC



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