Good Morning America aired from its brand-new studio at the Robert A. Iger building in New York City on Monday, June 16; To celebrate the relocation, some friendly faces from ABC

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.

“My left side is functioning, my right side has completely stopped working,” the Grey’s Anatomy alum said, after sharing he only had “one functioning arm,” in an interview with Diane Sawyer that aired...

“She is probably my biggest champion and my most stalwart supporter, and I lean on her.”