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.

Eric Dane is opening up about his ALS diagnosis. The Grey's Anatomy alum sat down with Diane Sawyer for Good Morning America in his first TV interview since revealing his diagnosis in April. The full interview will air Monday, but in a brief teaser clip posted online, Dane remained optimistic about his future.