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.

Eric Dane is opening up about his ALS diagnosis, two months after he publicly shared his health news with the world. The “Grey’s Anatomy” star, who is 52, said in a new interview with Diane Sawyer on “Good Morning America” that he originally dismissed his initial symptoms.

Dane is set to share intimate details about his diagnosis in a new "Good Morning America" interview with Diane Sawyer.