[Prion diseases and a new variant of Creutzfeldt-Jakob disease]

The causal link of a new variant of CJD (v-CJD) with bovine spongiform encephalopathy (BSE) has led to world-wide panic. BSE emerged in 1986 through dietary products contaminated with scrapie pathogen, BSE case reports increased in number up to 37,000/year in 1993, then declined in 1994 when the first case of v-CJD emerged. There is a 3-year gap between the emergence of BSE and the introduction of a ban on the use of specified bovine offal in human food. People might have consumed dietary products contaminated with BSE pathogen for the period. Species barrier which has protected human from being transmitted with sheep scrapie pathogen might not work so well in cow-to-human transmission as in sheep-to-human. There are familial forms and sporadic forms of human prion diseases. The familial prion diseases are always related to prion protein (PrP) gene mutations. Sporadic forms of prion diseases are composed of sporadic CJD, iatrogenic CJD and kuru. Sporadic CJD occurs in elder people and shows cortical signs and periodic synchronous discharges (PSD) in short clinical course and pathologically spongiform degeneration and abnormal PrP deposition in synapse structures, but no amyloid plaque deposition in the brain is observed. Since the v-CJD patients had no mutations in PrP gene, v-CJD belongs to sporadic forms of prion diseases. v-CJD shows quite different clinicopathological features from those of sporadic CJD, rather shows similar features to iatrogenic CJD of pituitary hormone and kuru. These three diseases share several features, which are younger patient age, main clinical manifestation of cerebellar signs, negative or rare record of PSD, and PrP amyloid plaque deposition in the brain. The patients of v-CJD, however, had no history of exposure to iatrogenic factors and of cannibalism. Also they did not have a valine polymorphism at PrP codon 129 which is frequently observed in the patients with iatrogenic CJD and kuru. Thus, v-CJD is a quite novel entity in human prion diseases.