UPDATE: 'I feel normal now,' former UDP patient says

[cnn-photo-caption image=http://i2.cdn.turner.com/cnn/2010/images/09/30/sallybetter.093010.cnn.jpg caption="Sally Massagee sit down with CNN's Anderson Cooper and Dr. Sanjay Gupta on Thursday night's AC360°." width=300 height=169]

Martina Stewart
AC360° Digital Producer

Editor's Note: Watch Sally Massagee's sit down with Anderson Cooper and Dr. Sanjay Gupta

New York (CNN) - A woman who suffered for years from a mysterious disorder that caused out-of-control muscle growth tells CNN's Anderson Cooper that her life is finally returning to normal.

Related: Dr. Gupta's Reporter's Notebook: Practicing medicine on the fringe

Four years ago, Sally Massagee began a medical quest, with the support of her family, to find help for her unexplained disorder.

She headed first to Duke University Medical Center. For two years, she saw doctor after doctor and had test after test, but no one at Duke could figure out what was happening to her body. After Duke came up empty, Massagee applied to the the Mayo Clinic in Rochester, Minnesota. But they rejected her because she did not have a diagnosis.

In 2008, she got a glimmer of hope. With a referral from her endocrinologist from Duke, she was accepted into the Undiagnosed Diseases Program at the National Institutes of Health.

After undergoing a battery of tests at UDP, Massagee had a long and nerve-wracking wait. And, in May of last year, she got the call she'd hoped for - her mystery was solved. The elite group of scientists and doctors at the UDP discovered that abnormal proteins which normally attack the organs, were, instead, attacking Massagee's skeletal muscles and causing every muscle in her body to grow out of control. Once she was diagnosed, Massagee had chemotherapy and a stem cell transplant to help fight the disorder which has no cure.

Related: Woman bulks up uncontrollably

"I feel normal now," Massagee tells Anderson Cooper in an exclusive interview that airs Thursday on AC360°, "I feel a hundred percent which is really great."

CNN Chief Medical Correspondent Dr. Sanja Gupta joined Massagee for the sit down and explained that her bulking muscles were far from a blessing.

"The protein is actually making her muscles probably weaker," Gupta told Cooper about Massagee's former condition. Notwithstanding the excessive muscle growth, "she's not getting stronger," Gupta said, "She's getting less limber, weaker. And just the simplest things become impossible to do. It can get worse than that even. Those muscles can get so big that they can start to actually crush somebody, including the rib cage and some of the internal organs . . . That's how bad it can get."

Watch a special hour-long version of AC360°'s "Doctor Detectives" Friday, October 1 on CNN at 8 p.m. and again at 11 p.m.

–AC360° Producer MaryAnne Fox contributed to this report.