Rare Diseases: Basic Information

What qualifies a disease as rare?

A rare disease occurs in less than 200,000 individuals in the United States, or less than 5 per 10,000 individuals in the European Union. As you might guess, there are some diseases that only affect small numbers of individuals in the world. And there are some diseases that are truly one-of-a-kind, usually happening because of a genetic defect. Some diseases are widespread in certain parts of the world but rare in others. It is estimated that there are between 5,000 and 8,000 known rare diseases in the world.

I want to know if a particular disease is considered rare.

The U.S. Office of Rare Diseases has a listing of over 6,000 diseases considered rare in the United States.

I need information on a rare disease.

You can look up the information alphabetically by disease name. If you don't know the name or how to spell it, you can look at the types of diseases page on this site for listings grouped by type (for example, neurological disorders, skin disorders, etc.).

I need information on a rare disease not yet listed on your site.

The About.com Rare Diseases site is always expanding, but if you can't find what you need, check these sites:

• In the United States: National Organization for Rare Disorders Rare Disease Database
• In the U.K.: Contact a Family Index of Specific Conditions and Rare Disorders
• In Europe: Orphanet - accessible in 6 languages: English, French, German, Italian, Spanish and Portuguese.

How can I find a support group for a particular disease or disorder?

First, look for an article about the disorder on the site. You can look at the types of diseases page on this site for listings if you don't know the name of the disorder. The article will contain a link to support groups. If there is not yet an article about the disorder, try the page of Support Groups resources, which links to various U.S. and international rare diseases support groups.