Retrospective outcomes studies for orphan diseases: challenges and opportunities

Retrospective outcomes studies for orphan diseases are scarce in the literature because of the significant methodological and data challenges that researchers have to overcome. Over the last two decades, many opportunities have emerged to mitigate these challenges. In this editorial we examined the common challenges in retrospective outcomes studies as well as the emerging opportunities that researchers can utilize to overcome those challenges. With the introduction of two retrospective orphan disease studies in this issue, we encourage more researchers to take advantage of the emerging opportunities to conduct and publish more retrospective outcomes studies for orphan diseases. This can provide important real-world insights into orphan diseases, including how they are being treated.