Could novel genomic alterations clarify phenotypic heterogeneity and aetiology in human prion diseases?

Abstract

Prion diseases, or transmissible spongiform encephalopathies, are a group of rare fatal invariably neurodegenerative diseases that occur in humans and animals. Prion diseases are characterized by neurodegeneration that generally have a sponge-like appearance. The infectious prion protein forms aggregates and accumulates in tissue. A unique feature is the manifestation of three prion disease forms; sporadic, acquired and genetic. High levels of heterogeneity are observed in the disease phenotype, age at onset (sporadic and genetic) and incubation period (acquired). In the majority of cases there is an absence of positive family history. For sporadic forms there is no known aetiology, the cause of acquired forms is by transmission and the genetic forms by mutations in the PRNP gene. Age at onset is an important factor in the disease and an improved understanding of the reported variance is necessary. Here, an in-depth literature review is presented on the phenotypic heterogeneity in regards to the age at onset and incubation period in human prion diseases. Modifying factors and novel genomic alterations concerting the phenotypic heterogeneity are discussed. In addition, novel genomic alteration concerting the aetiology of sporadic human prion diseases is discussed.