In the U.S., any disease affecting fewer than 200,000 people is considered rare. This definition comes from the Orphan Drug Act of 1983 and is slightly different from the definition used in Europe. There are nearly 7,000 rare diseases affecting nearly 30 million Americans. In other words, almost one in ten Americans are suffering from rare diseases.
Besides dealing with their specific medical problems, people with rare diseases struggle to get a proper diagnosis, find information, and get treatment. The rarity of their conditions makes medical research more difficult.