My first encounter with prion diseases dates to 1986. As a clinical resident in neuropathology, I was tasked with performing autopsies of patients who died of mysterious brain diseases. In his early 60s, my patient had developed a form of dementia that progressed at a terrifyingly rapid pace and eventually led to his death. I sampled the patient's brain and processed it for histological examination. The microscope revealed an eerie landscape of destruction. All that was left in the patient's cortex were astrocytes and microglia, and the few remaining neurons showed extensive vacuolation of their bodies and processes. Such blazing destruction of the brain was indicative of just one diagnosis: Creutzfeldt-Jakob disease, a spongiform encephalopathy caused by enigmatic infectious agents called prions.