Eric Dane, best known for his work on “Grey’s Anatomy,” opened up about his amyotrophic lateral sclerosis (ALS) diagnosis while on “Good Morning America” on Monday morning.

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.