Mystery illnesses are not just fodder for television. There are real, undiagnosed illnesses that are important to solve for public health.

One way that NIH tackles mystery diseases is through its Undiagnosed Diseases Program. The program focuses on the most puzzling medical cases referred to the NIH Clinical Center in Bethesda, Maryland. It was founded in 2008.

NIH leaders, including William Gahl, M.D., Ph.D., National Human Genome Research Institute's (NHGRI) clinical director and head of the program, recently did an "Ask Me Anything" discussion on Reddit.

We thought we'd provide our own question and answer overview for readers on the unique program.

Who leads the program?

The program is organized by the National Human Genome Research Institute, the NIH Office of Rare Diseases Research, and the NIH Clinical Center.

While the program started at the NIH Clinical Center in 2008, it expanded into a network of seven clinical sites throughout the U.S. in 2012. These sites are collectively known as the Undiagnosed Disease Network.

What happens to a patient in the program?

The patient visits one of the Undiagnosed Disease Network centers for about a week. During their visits, a large medical team—with a deep base of knowledge about rare and common diseases—examines them. This team of NIH experts studies a patient's clinical and laboratory results for important clues following the patient's visit.

What are some of the program's goals?

The program offers patients the hope of a diagnosis and the possibility of treatment strategies. In return, patients provide researchers the opportunity to learn more about diseases and what causes them.

How many patients are seen each year?

As of 2014, the annual patient visit rate was 130.

How many cases are solved?

The number of cases closed with no diagnosis is approximately 25 percent. However, the number of cases that are pending diagnosis with strong leads is 60 percent.