Grey's Anatomy star Eric Dane details subtle first symptom he experienced before heartbreaking ALS diagnosis

Eric Dane opened up about his diagnosis in a new interview and spoke of the realization that something wasn’t right.

Actor Eric Dane, recognized for his role as Dr. Mark Sloan on Grey’s Anatomy, announced that he was diagnosed with ALS (amyotrophic lateral sclerosis) back in April.

The degenerative health condition affects nerve cells in the brain and spinal cord and gets worse over time.

The 52-year-old Californian asked for privacy after issuing a brief statement, confirming his diagnosis.

At the time, he said: "I have been diagnosed with ALS. I am grateful to have my loving family by my side as we navigate this next chapter.

"I feel fortunate that I am able to continue working and am looking forward to returning to set of Euphoria next week.

"I kindly ask that you give my family and I privacy during this time."

Dane revealed the first symptoms he noticed over a year ago(Good Morning America)

However, the actor spoke on Good Morning America on Monday (June 16), and revealed the first signs that made him concerned for his own health.

He said: “I started experiencing some weakness in my right hand and I didn’t really think anything of it at the time.

“I thought maybe I had been texting too much or my hand was fatigued.

“But a few weeks later I noticed it had gotten a little worse so I went and saw a hand specialist and he sent me to another hand specialist.

“I went and saw a neurologist and they sent me to another neurologist and said this is way above [his] pay grade.”

After nine months of searching for answers, the actor was finally diagnosed with ALS.

Now, a year on from the first symptoms, Dane said: “I have one functioning arm, my dominant side is [my right], my left side is functioning, my right side is completely stopped working.

Dane said the idea that he will eventually lose the movements of both arms and then legs is 'sobering' (Good Morning America)

“My left arm is going, I feel like a couple few more months and I wont have my left either, it is sobering.”

ALS, often referred to as Lou Gehrig's disease after the baseball player who suffered from it, affects muscle control that starts small - like twitching and weakness in an arm or leg, or difficulty swallowing or speaking - before slowly affecting the muscles needed to move, speak, eat, and breathe.

This often proves particularly difficult on those who suffer with it as they eventually become paralyzed, despite still maintaining normal brain activity and functionality.

The disease is fatal and has no cure with people living three to five years after diagnosis, according to the Muscular Dystrophy Association, though some sufferers can live for many years.