Prion diseases

Prion diseases are transmissible and fatal neurodegenerative diseases affecting humans and animals, in which the infectious agent is composed of misfolded and multimeric forms of cellular prion protein. These conditions can be sporadic, inherited or acquired. Rapidly progressive dementia and ataxia are the common themes in the clinical presentation, but these can be accompanied by a wide variety of neurological or psychiatric syndromes. Neuropathological examination of brain tissue remains the only way of making a definite diagnosis, but major advances in magnetic resonance brain imaging, such as diffusion-weighted sequences, and cerebrospinal fluid prion amplification assays have proved to be reliable ante mortem diagnostic tools. Prion protein gene (PRNP) analysis is also recommended, to rule out Mendelian forms and provide the codon 129 genotype, which has profound effects on incubation period, susceptibility, duration of illness, clinical phenotype and neuropathology. At present, there is no effective treatment for prion disease.