The many faces of human prion diseases in Belgium and the world.

Prion diseases are rare neurodegenerative disorders that always lead to death and that can be transmissible under certain conditions. Although sporadic Creutzfeldt-Jakob's disease (CJD) is the best known human variant of these transmissible spongiform encephalopathies with an incidence of about 1 in 106 inhabitants, several other types of human prion disease have been described (e.g. Familial CJD, Gerstmann-Sträussler-Scheinker syndrome, Fatal Familial Insomnia,...). In 1996, a variant of CJD has been linked to the epidemic of bovine spongiform encephalopathy (BSE). Therefore, vigilance concerning prion diseases was increased throughout the whole of Europe. In Belgium, a comprehensive, nation-wide study has been conducted both retrospectively (1960-1997) and prospectively (1998-...) to identify prion disease patients. In 1998, a surveillance system has also been created to monitor the incidence of CJD and other prion diseases. Using data from both studies and the surveillance program, the occurrence and phenotype of all types of prion diseases in Belgium was investigated. The sporadic type of CJD was identified in 116 patients, while 4 suffered from a hereditary form. In our series, we could find no evidence for variant or iatrogenic CJD, neither for the more rare types of prion diseases.