"20/20: MEDICAL MYSTERIES" REPORTS ON SOME OF THE STRANGEST CASES KNOWN TO MEDICINE, FRIDAY, MARCH 28 AT 9:00 P.M. ON ABC

From living life without arms or legs to unstoppable hair-pulling, "20/20" reports on rare medical cases and conditions that even doctors can barely understand, on a special edition of the show, FRIDAY, MARCH 28 (9:00-10:00 p.m., ET) on the ABC Television Network.

"20/20: Medical Mysteries" reports include:

� Living without limbs: All parents holds their breath at that moment of birth, and then begin counting� ten fingers, ten toes. But what if there were no arms or legs? Bob Brown reports on a man born that way, and how he uses his voice to make a difference.

� Gay at a young age: A medical mystery and one of the biggest debates of our time: Is there a gene that determines whether you are gay or straight? Is sexual identity biological or a learned behavior? Lynn Sherr reports on several kids who knew they were gay from a very young age.

� Pregnant man: This week's most talked-about medical item -- a transgendered man who is pregnant. Now living as a man, he was born a woman. But when his wife couldn't conceive, they decided, since he still had a uterus and ovaries, that he would carry their baby. He's due in July.

� Hair pulling: What could cause a beauty queen and a chic Hollywood stylist to pull out their own hair -- repeatedly, uncontrollably, even as they fight the urge to do it? It's called "trichotilomania" and it's a compulsion that doctors still don't understand. Somehow the wiring in their brains makes them pull out the hair on their heads, their eyebrows, even their eyelashes. JuJu Chang reports.

� Vitiligo: Imagine white spots showing up on your body, at first just one or two, but then they grow and soon others follow, taking over the pigmentation of your body. As Elizabeth Vargas reports, Vitiligo is a mysterious disease for which there is no cure. While it may not be life threatening, Vitiligo can be psychologically devastating, altering one's appearance and sometimes even threatening to up-end one's very identity -- from African-American to what looks like "white."

"20/20" is anchored by Elizabeth Vargas and John Stossel. David Sloan is executive producer.