Human prion diseases

The term 'prion diseases' refers to a group of neurodegenerative disorders thought to be caused by prions, pathogenic agents with novel modes of repli cation and transmission. Prion diseases are characterized by long incubatio n periods ranging from months to years and are invariably fatal once clinic al symptoms have appeared. They are also called transmissible spongiform en cephalopathies (TSE), on account of the predominant neuropathological chang e observed in the central nervous system. The most important members of thi s group are Creutzfeldt-Jakob disease (CJD) of man displaying sporadic, inh erited and infectious forms, bovine spongiform encephalopathy (BSE, 'mad co w disease') of cattle, and scrapie of sheep. Despite their rarity, human pr ion diseases have recently been covered extensively in the media because of the likely connection between a new variant of human CJD (vCJD) and BSE an d the possibility of contamination of human blood and blood products by the vCJD agent. This short review discusses the basic biological properties of prions, followed by a presentation of the clinical and pathological featur es of the most important human prion diseases.