A rare disease, also referred to as an orphan disease, is any disease that affects a small percentage of the population. Most rare diseases are genetic, and thus are present throughout the person’s entire life, even if symptoms do not immediately appear. Many rare diseases appear early in life, and about 30 percent of children with rare diseases will die before reaching their fifth birthday.This list was derived from the Orphanet rare disease nomenclature which is comprised of a heterogeneous typology of entities of decreasing extension, including: groups of disorders, disorders, sub-types. A disorder in the database can be a disease, a malformation syndrome, a clinical syndrome, a morphological or a biological anomaly or a particular clinical situation (in the course of a disorder). They are organised into groups, and further divided into clinical, etiological or histopathological sub-types.