The mysterious prion diseases--a historical perspective.

The spongiform encephalopathies are a group of diseases sharing a common pathology and affecting both humans and animals. The human diseases include both sporadic and familiar disorders. Creutzefeld-Jakob disease and kuru are sporadic, familial Creutzfeld-Jakob, fatal familial insomnia and the Gerstmann-Sträussler-Scheinker syndrome are genetic and inherited as autosomal dominants. The hallmark of these diseases is the presence of abnormal forms of a membrane protein called prion, particularly abundant in the brain. Transmission of these diseases has been documented from humans to humans, from humans to animals and, more controversially, from animals to humans. Many questions in the aetiology and pathogenesis remain unanswered.