Prion diseases comprise a group of fatal transmissible neurodegenerative diseases of both humans and animals that can have an infectious, genetic, or idiopathic origin. They are caused by an unusual transmissible agent that has been termed prion and may occur as acquired, idiopathic, or hereditary diseases. The key event in the pathogenesis of all forms of these diseases is the conformational conversion of a normal cell surface glycoprotein [cellular isoform of the prion protein (PrP C )] into a pathogenic isoform [scrapie isoform of PrP (PrP Sc )] that has a high content of beta-sheet. These diseases are characterized by the cerebral deposition of an aggregated pathological isoform of the prion protein termed PrPSc. Prion diseases include Creutzfeldt–Jakob disease (CJD) in humans as well as bovine spongiform encephalopathy and scrapie in animals. 

Prion病指一组发生于人类和动物的致死性传染性神经系统变性疾病，这类疾病可具有感染、遗传或原发性病因，由一种被称为朊蛋白（prion）的异常传播性病原所致，可以是获得性、原发性或遗传性疾病。这类疾病的病理成因关键是正常的细胞表面糖蛋白（朊蛋白的细胞异构体PrP C）发生了构型转变，变为含有大量的beta-折叠结构的病理性异构体(朊蛋白的瘙痒病异构体PrP Sc)。Prion病主要特征为异常朊蛋白PrP Sc在大脑的病理性沉积，包括发生于人类的克－雅氏病（Creutzfeldt–Jakob disease，CJD)以及动物中发生的牛海绵状脑病和瘙痒病等。