dr. william gall and his team of world class specialists at the undiagnosed diseases program was trying toolve the mystery. >> this is super impressive. i mean, you literally see a cleavage right in the middle of her back because those muscles are so big. dr. william gall, the program investigator. >> bottom line, it's not acromegaly, just confined to the muscle, what in the world could this be? >> at the undiagnosed diseases program, sally went through a gruelling week of exams and tests, including a muscle biopsy that proved to be the key to the mystery. sally got the diagnosis she was so desperate for, led to a stem cell transplant a little more than a year ago. sally came to new york this week to show sanjay and me just how much better she is today. it's great to see you smiling and happy. >> thank you. it's great to be here. >> the last time we saw you, you said things were improving slowly, little by little. how about today? >> they continue to improve. it's very exciting. i feel normal now. i feel 100%, which is really great. >> i heard you had a big moment this morning. >> yes. i w

dr. william gall leads an elite team of doctors, specialists and researchers. they are the best in the world. >> she often turns this foot in. >> reporter: together they focus their vast expertise to try to save patient's lives. >> looser. >> reporter: they are detectives in search of clues to solve mysteries no other doctors could solve. >> you're talking 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 10%, 15% or so. >> reporter: but 10% or 15% is a bright ray of hope for some patients. >> how much more you can do physically really speaks volumes. >> yeah. >> reporter: sally massagee had all but given up. take a look at her back. it was as if muscle mass was consuming her body. sally was transforming into the incredible hulk. so this is sally's mri of the brain. that's incredible. >> even the muscles that govern the movements of the eye