Gerstmann-Sträussler-Scheinker disease (GSS) is a hereditary transmissible spongiform encephalopathy associated with prion protein gene mutation P102L. The age of onset is roughly restricted to around the sixth decade; however, it is unclear whether the disease-specific pathology of GSS is already evident in the pre-clinical stage. We had a chance to examine an autopsy case with PRNP P102L mutation. The patient had died at 50 years of age before the clinical symptoms of GSS had appeared; neither neuronal loss, gliosis nor spongiform change was found anywhere in the brain. Immunohistochemistry failed to detect any deposition of prion protein. It is thus considered that amyloid plaque formation in GSS probably develops in a relatively rapid fashion compared with Alzheimer's disease. Although the patient suffered from schizophrenia, no significant pathological changes were detected except for astrocytic inclusion bodies in the cerebral cortex. The nature and significance of the inclusion bodies, which are not observed in patients with GSS, remain unclear.