The European Union defines a disease as rare when it affects fewer than 5 per 10 000 persons,1 whereas the USA considers a condition rare if it affects fewer than 200 000 individuals.2 To date, however, there is no terminology to appropriately address these diseases as a category other than rare diseases, or in some instances orphan diseases when referring to conditions that lack the resources for treatment discovery. Even though these terms have helped thus far to describe ...READ MORE »