Though the terms "case study" and "case report" have been used interchangeably in the past, their difference lies in the approach. Case reports contain a detailed description of a single patient’s unique clinical findings (diagnosis, treatment, and outcome). Case studies, on the other hand, tend to involve a much deeper qualitative exploration into the case or cases involved. ^[2] Case series involve a small collection of patients who share a common clinical feature, such as a rare condition or response to a novel therapy.^[3] In short, case studies are a more qualitatively deeper cousin of the case report, while case series are a collection of more closely related case report siblings.

The lack of a control group plus the descriptive approach of all three study types means that they can detail observations, but they cannot establish causation. Even in instances where causation may seem likely, the small number of patients involved means they are not suitable for application to a broader population. However, they are each valuable to help clinicians learn from rare or unusual instances in practice.