[Prion disease--the present status and recent progress in Japan]

There have been identified 1051 cases of prion dsease in Japan since 1999 by the surveillance committee, of which idiopathic prion disease held 77.8%, hereditary 15.9% and infectious 6.6%. Idiopathic prion disease is sporadic Creutzfeldt-Jakob disease (sCJD) and most sCJD cases were classified into MM1 presenting with classical clinical features. MM2, MV2, VV1 and VV2 sCJD cases were rare and showed atypical features including prolonged course, lack of myoclonus and absence of PSD. In such occasions, high signal intensities on DW-MRI as well as increased 14-3-3 and tau proteins in CSF were very helpful. MM2 tharamic sCJD may lack all these laboratory findings but reduction of tharamic CBF in SPECT or PET would support the diagnosis. Hereditary prion disease are classified into 3 major phenotypes such as familial CJD, Gerstmann-Straeussler-Scheinker disease (GSS) mainly showing spinocerebellar ataxia, and fatal familial insomunia. While there have been known many mutations of prion protein gene, only V180I (fCJD), E200K (fCJD), M232R (fCJD) and P102L (GSS) mutations were common. Because most cases did not have family history, genetic test is mandatory in all the cases of prion disease including seemingly "sporadic" CJD. All the cases but 1 case of variant CJD were dura-grafted CJD in infectious prion disease.