[Prion diseases in Japan: analysis of 918 patients].

The Creutzfeldt-Jakob Disease (CJD) Surveillance Committee, Japan, started in April 1999, and has identified 918 patients with prion diseases until March 2007, including 716 with sporadic CJD (78.0%), 128 with genetic prion diseases (14.0%), and 72 with environmentally acquired prion diseases (7.8%). Among atypical cases of sporadic CJD, most common was MM2 type including thalamic and cortical forms. The 128 genetic cases were classified to 42 with CJD with a PrP V180I mutation (32.9%), 26 with CJD with a E200K mutation (20.4%), 25 with GSS with a P102L mutation (19.6%), 17 with CJD with a M232R mutation (13.3%), 4 with a insertion mutation in the octapeptide repeat region (3.1%), 3 with GSS with a P105L mutation (2.5%), 2 with fatal familial insomnia with a D178N mutation (1.8%), and so on. The 72 patients with environmentally acquired prion diseases included 71 with dural graft-associated CJD (dCJD) and one with variant CJD (vCJD). Taken together with the results by the previous surveillance systems, a total number of dCJD in Japan was 129. The vCJD patient had a history of short stay in the UK and presented with periodic electroencephalogram in the late stage, requiring revision of the vCJD case definition (WHO 2001).