Creutzfeld-Jakob disease (CJD) is a transmissible spongiform encephalopathy. Until the 1990s, three forms of CJD were recognized: sporadic disease, which accounted for the majority of cases and was of unknown origin; familial cases, associated with a gene mutation; and iatrogenic cases, caused by accidental transmission of the causative agent via contaminated instruments or certain transplants. Most cases were seen in people over 50 years of age, and were characterized by personality changes and progressive dementia. Death usually occurred within one year.
In the 1990s, a variant of CJD was recognized (vCJD), which was strongly linked to exposure – probably through food – to a disease of cattle, bovine spongiform encephalopathy. vCJD tends to affect younger patients than classical CJD, and to have a longer duration. Early symptoms include depression or, occasionally, a schizophrenia-like psychosis. As the disease progresses, patients develop more and more neurological signs, including unsteadiness, difficulty walking and involuntary movements.