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Variant Creutzfeldt-Jakob disease (vCJD) is a zoonotic disease caused by cross-species transmission of bovine spongiform encephalopathy with a median age at onset of 27 years. In 1996, when the first cases were described, a clinicopathological phenotype distinct from sporadic CJD was defined and diagnostic criteria with a high sensitivity and specificity for vCJD have been validated.1
All definite and probable cases of vCJD (201/218) have been methionine homozygous (MM) at codon 129 of the prion protein gene (PRNP). If cases with the other PRNP-129 genotypes (MV, VV) have longer incubation periods, and are exposed at the same age, they will be older by the time they develop symptomatic disease. In addition, patients over 50 are more likely undergo surgical procedures and receive blood transfusions than younger patients and are, therefore, at greater risk of secondary vCJD. Future vCJD cases are likely to occur in older groups than in the primary epidemic. An important question is whether these patients have the same clinical phenotype and pattern of investigation findings as previously described.
A review of the 177 probable and definite vCJD cases referred to the UK surveillance system between 1995 and 2014 identified six cases aged over 55 years at the onset of symptoms.
All the cases developed progressive cognitive impairment and additional neurological features which are unusual in the more common forms …