Dane -- who shot to fame amid six seasons on the hit ABC drama "Grey's Anatomy," where he played Dr. Mark Sloan, affectionately known as "McSteamy" -- said his symptoms began over one year ago, when he began to experience weakness in his right hand.

Now, however, the actor has shared a few more sobering updates about his health on Good Morning America. “My right side has completely stopped working,” he told the program. Dane said that he expects to lose control of the left side as well.

"I feel like maybe a couple, few more months, and I won't have my left hand either," the 'Grey's Anatomy' alum said, adding that he worried about losing the use of his legs, in a sobering interview that aired on Monday's 'Good Morning America.