An undiagnosed disease is a medical condition without a known cause despite a lot of evaluation. A condition is likely to be undiagnosed if it is rare (especially ultra-rare or difficult to diagnose), has an atypical presentation of a known disorder, or has not yet been described. Considering that 85% of the over 7,000 identified rare diseases affect less than one in a million people, most doctors will never see two patients with the same ultra-rare disease.
Patients with an undiagnosed disease experience a “diagnostic odyssey” where they spend years or decades going from doctor to doctor seeking answers. This odyssey can cause patients to experience significant emotional, mental, physical, and financial distress. Obtaining a diagnosis can give patients an idea of what their future holds, guidance for family planning, validation for their symptoms, a disease support community, a medical home, hope for treatment, and more.
Statistics from the Undiagnosed Diseases Network (UDN) can provide additional insight into undiagnosed diseases. Since its founding 10 years ago, the UDN has received 6,194 applications, accepted 2,457 applicants, evaluated 2,103 participants, and diagnosed 627 people. Most diagnosed patients have a condition with a genetic etiology.