Abstract: Disclosed is a system and method for developing a differential diagnosis list or disease ranking in a list of differential diagnosis or identifying a unique disease process when the etiology of patient's presentation is unknown. In one example, the method receive one or more symptoms of a patient, determines a set of diseases having at least one clinical feature that overlaps with the patient's symptoms, determines a ratio of prevalence for each respective disease to a cumulative prevalence of the set of diseases, determines a respective relative probability score for each disease of the set of diseases in view of the ratio of prevalence, determines a ranking of the diseases of the set of diseases in view of the relative probability scores, and outputs the ranking of the diseases.