PRNP and prion disease: Generally, CJD is defined as spongiform encephalopathy, GSS as an encephalo(myelo)pathy with multicentric amyloid plaques, FI as predominantly thalamic degeneration with a relatively characteristic clinical syndrome either lacking or associated with a specific mutation in the PRNP (D178N associated with methionin at the polymorphic codon 129) [12,13].