Transmission of prion infection was attempted using brain tissue from a human patient with familial prion disease who was heterozygous for a mutant PRNP allele (Y226X) resulting in expression of truncated PrP protein . This patient died at age 57 after a 27-month course with severe progressive memory and visuospatial dysfunction followed by akinesis and mutism. By microscopic examination of the brain severe cerebral amyloid angiopathy (CAA) was seen in numerous areas, and amyloid was intensely stained by anti-PrP antibodies. Small focal tau accumulations were also noted but neurofibrillary tangles were absent.