Rare Diseases and Related Terms
Rare diseases terms are either (1) terms for which information requests have
been made to the Office of Rare Diseases Research, the Genetic and Rare Diseases
Information Center, or the National Human Genome Research Institute; or (2)
diseases that have been suggested as being rare. The purpose of the Rare
Diseases and Related Terms list is to distribute information; although the list
is updated regularly, it should not be used as a reference or guarantee that a
condition is rare. The prevalence of a rare disease is usually an estimate and
may change over time. A rare (or orphan) disease is generally considered to have
a prevalence of fewer than 200,000 affected individuals in the United States.
Certain diseases with 200,000 or more affected individuals may be included in
this list if certain subpopulations of people who have the disease are equal to
the prevalence standard for rare diseases. We welcome suggestions for additions
to or deletions from the list. Your recommendations may be sent via e-mail to
ord@od.nih.gov
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