AbstractHuman prion diseases (HPDs) are progressive and fatal neurodegenerative diseases caused by abnormal prion protein (PrPSc). They can be sporadic, genetic or acquired. Sporadic HPDs include sporadic Creutzfeldt–Jakob disease (CJD) and sporadic fatal insomnia. Genetic HPDs include genetic CJD, Gerstman–Sträussler–Scheinker disease and fatal familial insomnia. Acquired HPDs include Kuru, variant CJD and iatrogenic CJD. The World Health Organization clinical diagnostic criteria for HPDs include clinical findings, cerebrospinal fluid protein markers and electroencephalography, and the UK and European clinical diagnostic criteria include a combination of clinical findings, 14‐3‐3 protein in the cerebrospinal fluid, magnetic resonance imaging diffusion‐weighted imaging and electroencephalography. Recently, the development and clinical application of real‐time quaking‐induced conversion has allowed pre‐mortem diagnosis of sporadic CJD. The real‐time quaking‐induced conversion assay allows detection of >1 fg of PrPSc in diluted CJD brain homogenate, as well as a variety of biological tissues and cerebrospinal fluid. However, the real‐time quaking‐induced conversion assay does not provide prognostic data and has lower diagnostic accuracy for some rarer, atypical prion diseases. Furthermore, recent advancements in laboratory testing and magnetic resonance imaging diffusion‐weighted imaging have shown improved diagnostic accuracy for prion diseases. Clinical trials of prion disease treatments have recently begun in many countries. The therapeutic window consists mainly of the early stage of disease, and few clinical studies have examined the role of biomarkers at this stage. Therefore, biomarkers, imaging and clinical symptoms might be extremely important for the diagnosis of prion diseases.Clinical trials of prion disease treatments have recently begun in many countries. The therapeutic window mainly consists of the early stage of disease, and few clinical studies have examined the role of biomarkers at this stage. Therefore, biomarkers, imaging and clinical symptoms might be extremely important for the diagnosis of prion diseases.