dr. william gault leads an elite team of doctors and researchers. they are the best in the world. together they focus their vast expertise to try to save patients' lives. they are detectives in search of clues to solve mysteries no other doctors could solve. >> you're talk about patients who have been seen by some of the best in the country here. they're very good clinicians and diagnostic doctors everywhere. so you're taking the hardest of the -- the most challenging cases of all. >> we expect a high failure rate. we expect a success rate of perhaps 10%, 15% or so. >> the undiagnosed diseases program was launched only two years ago at nih. it accepts only the rarest of medical cases. it's not only about saves lives. here they're also hoping to discover new diseases and create new science. >> it's really sort of the inspiration that we all have as clinical researchers. >> in two years the udp has had more than 3,000 inquiries. more than 1,000 applications actually made it to dr. gaul's desk. >> this is an acceptance letter. >> but udp has accepted only a little over 300 patients.