Introduction
What is a rare disease?
Rare diseases are individually uncommon but collectively affect hundreds of millions of people worldwide. This page explains what qualifies as a rare disease and why dedicated information matters.
European definition
A condition affecting fewer than 1 in 2,000 people in the general population.
United States definition
A condition affecting fewer than 200,000 Americans at any given time (Orphan Drug Act, 1983).
300M+
People affected worldwide
7,000+
Known rare conditions
72%
Have a genetic origin
4–8 yrs
Average time to diagnosis
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