ABSTRACT Prion diseases are an important cause of rapidly progressive dementias. Among them, the most common is sporadic Creutzfeldt-Jakob disease (CJD). It is a rare and incurable disease, with rapid progression to death. Objective: To describe the diagnostic approach of a patient with Creutzfeldt-Jakob disease. Methods: The diagnosis is established through the clinical picture associated with characteristic changes in the brain magnetic resonance imaging, the electroencephalogram, and analysis of specific changes in the cerebrospinal fluid. Results: The present report describes the case of a 53-year-old patient in the city of Fortaleza-CE. The diagnosis was made based on the clinical condition and through diagnostic tests, including 14-3-3 protein and RT QUIC analysis. Differential diagnosis was performed with other rapidly progressive causes, such as infectious and immune-mediated diseases. Conclusions: The diagnosis of probable sporadic CJD was established.