"MY EXTREME AFFLICTION" - A LOOK AT AMAZING MEDICAL CONDITIONS AND UNBELIEVABLE ABILITIES, ON A SPECIAL EDITION OF "20/20, MARCH 17 ON ABC

"My Extreme Affliction" takes viewers into the lives of people with some of medicine's most extreme conditions or who have unbelievable abilities. The series looks back on some favorite reports and brings viewers some new unimaginable conditions. Chris Cuomo anchor's this week's "My Extreme Affliction," a two-hour Special Edition of "20/20," SATURDAY, MARCH 17 (9:00-11:00 p.m., ET) on the ABC Television Network. Reports include:

Twisted Cheerleader: Washington Redskins Cheerleader Ambassador Desiree Jennings, 25, had everything going for her until one day when her body suddenly stopped working, turning into a twisted, jerky mess. For some inexplicable reason, when Desiree runs, her body untwists and straightens out, and sometimes she can walk backwards and sideways without trouble. Footage of this phenomenon spread quickly online, making her an internet sensation. Was it caused by a flu shot as Desiree thought? Her journey for answers to this mystery takes her to a controversial osteopath in North Carolina and has led people questioning whether or not her affliction is real. Jim Avila reports. (OAD: 7/23/10)

Kids Too Nice to Be Normal: Williams Syndrome is a rare genetic condition -- so rare, in fact, that few people have ever heard of it. Of about 7,500 newborns, only one will have it. But that one, should you ever meet him or her, will likely have a personality of unforgettable ebullience and warmth. When Chris Cuomo attended a camp for children with Williams, he was besieged not by formal handshakes, but by hugs and slaps on the back and a barrage of questions: "What's your favorite color?" "Where do you live?" "Have you met Barney the Dinosaur?" How can the random deletion of just 25 out of 25,000 genes cause such unusual dispositions? "20/20" follows researchers, children and their families in their quest to make sense of a most unusual malady, and also looks at the darker side of this medical condition that forces those who have it to be friendly, even to total strangers. (OAD: 6/10/11)

Mega-Brain: On the outside, Daniel Tammet seems unremarkable, but behind his bookish exterior lies a superhuman gift, one of the most extraordinary brains man has ever seen. Tammet is a mathematical genius, capable of astronomical calculations instantly. He says he was born with the ability to experience numbers in an exceptionally vivid way, and is also a gifted linguist, speaking 9 languages. Yet because of his Asperger's diagnosis, he cannot drive a car. Nick Watt reports. (OAD: 6/1/10)

Tourettes: An estimated one in every thousand children has Tourette Syndrome, a neuro-biological disorder that is characterized by a range of symptoms ranging from painful self abuse and rage episodes to bizarre vocalizations like barking, meowing or even vulgar and profane language. The children are helpless to control the embarrassing behavior, which subjects them to painful ridicule from their peers and sometimes even adults. For families living with this disorder, it's an unimaginable reality. ABC News Correspondent Jay Schadler follows the stories of four girls and their families as they document intimate scenes from their lives in video diaries. The children poignantly discuss the most debilitating effects of Tourette Syndrome, including the emotional impact of social isolation that sometimes includes alienation from their own families. Even though this mystery disorder has no known cause or cure, the girls reveal an inner strength that empowers them to achieve their dreams. (OAD: 5/22/09)

David Sloan is executive producer.