PRNP and fatal familial insomnia: The PRNP gene (OMIM# 176,640) is associated with various types of hereditary neurodegenerative spongiform encephalopathies, including Creutzfeldt-Jakob disease (CJD), Gerstmann-Straussler Disease (GSD), fatal familial insomnia (FFI) and Huntington disease-like 1.