Some conditions present a complex set of symptoms and are relatively rare, so the body of knowledge necessary to diagnose and treat the condition does not yet exist. An undiagnosed disease means that the medical community cannot assign the symptoms to one particular disease biology, or give it a clear prognosis. More than 25 million Americans and their families are part of this group. Many are asked to participate in research studies focused on understanding their condition.

For more information, visit the National Human Genome Research Institute