A
rare disease or disorder is defined in the U.S. as one affecting fewer than 200,000 Americans. There are more than 6,000 known rare diseases, and it is estimated that about 25 million Americans are affected by them (as of 2002). Prior to the RDA was the
Orphan Drug Act of 1983, which was designed to facilitate the development and commercialization of drugs to treat rare diseases, termed
orphan drugs. This act, however, did not provide for the creation of a centralized structure able to coordinate research or recommend agendas that would better facilitate research and education. ==Legislative history==