We report on a novel subtype of Creutzfeldt-Jakob disease with a single proteinase K-resistant prion protein fragment of about 6 kDa in Western blots of brain homogenates. Clinically this patient showed a progressive spastic disorder and dementia over 3 years. No mutation of the prion protein gene was found. Since this patient had received a blood transfusion, an iatrogenic cause, albeit unlikely, cannot be ruled out. Future studies will have to be attentive to small prion protein fragments, which may cause or be associated with unusual clinical disease that might possibly only be diagnosed by immunoblotting of brain homogenates.