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The National Institutes of Health (NIH) Undiagnosed Diseases Program (UDP) is part of the Undiagnosed Disease Network (UDN), an NIH Common Fund initiative that focuses on the most puzzling medical cases referred to the NIH Clinical Center in Bethesda, Maryland. It was organized by the National Human Genome Research Institute (NHGRI), the NIH Office of Rare Diseases Research (ORDR) and the NIH Clinical Center.


A longstanding medical condition that eludes diagnosis by a referring physician can be considered undiagnosed and may be of interest to this clinical research program. Of the total number of cases that are referred to this program, a very limited number will be invited to proceed in the study following careful application review by the program's medical team. In general, it takes 8 to 12 weeks for the UDP to evaluate an application, and the waiting list for admission is 2 to 6 months.

The Undiagnosed Diseases Program pursues two goals:

  • To provide answers to patients with mysterious conditions that have long eluded diagnosis
  • To advance medical knowledge about rare and common diseases

For information, view our Frequently Asked Questions.

UDP Facts (2008-2014)

  • Inquiries: 9,300.
  • Applications: 3,100.
  • Acceptances: 750.
  • Patients seen or scheduled: 700.
  • Approximate annual patient visit rate: 130.
  • Approximate distribution of patients seen: 40 percent pediatric cases and 60 percent adult cases.
  • Percentage of cases resolved with a either a clinical, molecular or biochemical diagnosis: a range between 25 and 50
  • Number of cases closed with no diagnosis: approximately 25 percent.
  • Number of cases pending diagnosis with strong leads: approximately 60.
  • Range in time to reach a diagnosis: from one week to four years.
  • Types of DNA analyses conducted: million-SNP (single nucleotide polymorphism) array scans performed for approximately 1,600 individuals (patients and family members); whole-exome sequencing analyses performed for approximately 900 individuals.
  • The NIH Common Fund awarded $5.6 million for FY14 to the NIH Undiagnosed Diseases Program, a clinical site of the Undiagnosed Diseases Network.

How It Works

Individuals whose conditions have eluded medical diagnoses may apply to become UDP participants and, if invited, are admitted to the NIH Clinical Center in Bethesda, Md. Each patient undergoes a week of diagnostic tests and expert consultations provided for free at one of the world's largest medical research institutes.

The patient is examined by a multidisciplinary medical team with a deep base of knowledge about rare and common diseases. The team, drawn from various NIH institutes and centers, studies a patient's clinical and laboratory results for diagnostic clues while the patient is in the Clinical Center and in the weeks and months following their visit. Many medical specialties from other NIH research centers and institutes contribute the expertise needed to conduct the program, including endocrinology, immunology, oncology, dermatology, dentistry, cardiology and genetics, among the dozens of participating senior attending physicians.

Ultimately, the UDP offers patients the hope of a diagnosis and the possibility of therapeutic strategies. UDP participants may receive consultation regarding their treatment when they arrive for a UDP evaluation, but treatment is usually not provided as a component of the program. The treatment recommendations that NIH clinicians may offer remain the responsibility of the patient and the clinician who refers that patient to the UDP.

In return, patients provide UDP researchers the opportunity to gain new insights about genetic and biochemical mechanisms of disease and insights into normal cell biology, biochemistry and physiology. So far, UDP researchers have encountered patients with uncommon presentations of known disorders, multi-systemic complex disorders and new disorders that have never been diagnosed.

UDP clinical researchers are using advances in DNA sequencing to detect defects in genes that point to known disorders. These tools offer the potential for discoveries about the role of molecular and biochemical events that can cause disease and, eventually, the development of diagnostic and therapeutic approaches for rare and common diseases.

The caseload of the UDP is steadily growing, with more than 100 pediatric and adult patients added each year. The volume of applications from patients across the country, and abroad, has exceeded expectations, reflecting that the UDP fills an unmet need for undiagnosed patients.

Contact Information

Apply or learn more about being a UDP participant.


1-844-RING-UDN (1-844-746-4836)


  • May 28, 2009: Mystery Diseases
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Last updated: May 24, 2017