Which of the following is a characteristic feature of prion diseases?

Prion diseases are a group of progressive neurodegenerative disorders that are characterized by the accumulation of misfolded proteins known as prions. One of the most significant features of these diseases is their fatal nature. Patients afflicted with prion diseases, such as Creutzfeldt-Jakob disease, experience rapid neurological decline and the conditions invariably lead to death, often within months to a couple of years after symptom onset.

The mechanisms behind prion diseases involve the conversion of normal cellular prion protein into an abnormal, pathogenic form, which leads to brain damage. This damage results in severe neurological symptoms, including memory loss, changes in behavior, and impaired motor functions, indicating the progressive and irreversible nature of these diseases.

Thus, recognizing prion diseases as fatal is critical in understanding their implications for patient care, research, and public health discussions. The acknowledgment of their fatality helps to inform medical professionals and families about the disease's prognosis and the need for supportive care.