[Surveillance of prion diseases in Japan: analysis of 409 patients].

Since April 1999, prion diseases in Japan have been surveyed with the field investigation system by the Creutzfeldt-Jakob Disease (CJD) Surveillance Committee under the Prion Disease and Slow Viral Infection Research Committee sponsored by the Ministry of Health, Labor, and Welfare of Japan. By March 2003, a total of 409 patients with prion diseases were reported, including 324 with sporadic CJD (79.2%), 49 with inherited prion diseases (12.0%), and 36 with infectious prion diseases (8.8%). About 15% of the sporadic CJD cases presented with atypical clinical features [long clinical course to akinetic mutism (> 9 months) or absence of periodic synchronous discharges (PSD) on EEG], including thalamic form of CJD (MM2 type) in the autopsy verified cases. The 49 patients with inherited prion diseases were classified to 31 with familial CJD, 17 with Gerstmann-Sträussler-Scheinker (GSS) phenotype, and one with fatal familial insomnia; mutations in the prion protein gene included P 102L in 14 (28.6%), E200K in 13 (26.5%), V180I in 8 (16.3%), M232R in 3 (6.1%), P105L in 2 (4.1%), and so on. All the 36 patients with infectious prion diseases were iatrogenic cases due to cadaveric dura mater grafts. Taken together with the data by the previous surveillance system, a total of 97 dura mater cases has been reported in Japan; the latency period between receipt of a dura mater graft and onset of CJD was 122 +/- 53 months (mean +/- SD) including 275 months as the longest one. Fortunately, there was no case of variant CJD.