An article in the January 2, 2008, issue of New Scientist magazine, discussed the atypical case of a 39-year-old woman from the United Kingdom (UK) who died from the effects of variant Creutzfeldt-Jakob disease (vCJD). vCJD is the human form of mad cow disease, a degenerative and fatal brain disorder. A postmortem examination revealed a genetic variation that differs from the typical mode of transmission, making researchers question whether a new outbreak of the disease could occur in the future.
vCJD and mad cow disease belong to a group of rare disorders called prion diseases, or transmissible spongiform encephalopathies (TSEs). In addition to vCJD, TSEs in humans include CJD, which occurs spontaneously and is unrelated to mad cow disease. Bovine spongiform encephalopathy (BSE) is a type of TSE found in cattle. The vast majority of vCJD cases have occurred in the UK, where they have been linked to eating beef contaminated with BSE. So far, there have been 166 confirmed cases of vCJD in the UK; all have died.
The symptoms of vCJD and other TSEs occur when abnormal prion proteins in the brain fold and become misshapen. As they progress, they produce devastating results. The woman featured in the article first showed symptoms in January 1999, when she experienced visual problems. Within two months, she developed slurred speech, unsteady gait and memory impairment. She died in 2000, 14 months after the onset of symptoms.
Simon Mead, PhD, MRCP, of the Medical Research Council’s Prion Unit and Department of Neurodegenerative Disease, Institute of Neurology at the University College London, led a team of scientists who performed the autopsy, examined the woman’s brain and did a follow-up genetic analysis. They found that some features of the damaged brain were not typical of other vCJD cases. The genetic analysis raised even more questions.
What distinguishes this case from all other known cases is that the woman was the only one to carry the VV version of the prion gene. All the others carried the MM version of it. Approximately 40% of the population carry the MM type, while 10% carry the VV version.
Researchers and health officials expressed the need to further study this new prion strain and its association with BSE. Another possibility offered by Mead and other scientists, is that this may simply be a case of “sporadic CJD,” with no known genetic or environmental cause.
“Even if it is a vCJD in a VV individual ... we wouldn’t necessarily expect another big epidemic,” said Chris Higgins, PhD, chair of the Spongiform Encephalopathy Advisory Committee, which advises the UK government on BSE and vCJD. “The maximum number of cases we would expect would be about 160. Our guess would be it will be even fewer.”
In the U.S. there has been no reported case of vCJD transmission through the blood supply. However, tests are being developed to detect vCJD and vCJD infections in blood and plasma donors. A risk assessment performed by the U.S. Food and Drug Administration (FDA) stated that the threat of vCJD in plasma-derived factor products is exceedingly low but possibly not zero. Since 1999, the FDA has enforced donor deferral policies among all blood donations from people who lived in or visited the UK for three months or longer between 1980 and 1996.
Mead’s report, “Creutzfeldt-Jakob Disease, Prion Protein Gene Codon 129VV, and a Novel PrPSc Type in a Young British Woman,” was published in the December 2007 issue of the Archives of Neurology.
Source: Medical News Today and Guardian Unlimited, both dated January 3, 2008