Transcript for Selma Blair's courageous fight
an ABC news exclusive tonight. Extraordinary bravery from a face many will know about her battle with Ms. Actress Selma Blair speaking on camera for the first time about her personal struggle. Ms affects as many as a million Americans. It's a chronic, often unpredictable disease of the central nervous system, involving the brain, spinal cord and optic nerves and causing problems with vision, balance and muscle control. It affects so many in different ways and it can often be debilitating. Robin Roberts with Selma Blair and what she wants everyone to know. Reporter: An emotional return to the red carpet for actress Selma Blair. The 46-year-old, who is known for her roles in cult classics like "Cruel intentions," "Legally blonde" and "The sweetest thing" now facing a new challenge. How are you doing? I am doing very well. I am very happy to see you being able to, you know, just put out what being in the middle of an aggressive form of multiple sclerosis is like. So my speech, as you'll notice is, I have spasmodic dysphonia right now. Reporter: When you were first diagnosed, what initially went through your mind? I cried. I had tears. I wasn't -- they weren't tears of panic. They were tears of knowing I now had to give in to a body that had loss of control. And there was some relief in that. Because ever since my son was born, I was in an Ms flareup and didn't know. And I was giving it everything to seem normal. And I was self-medicating when he wasn't with me. And, you know, I was drinking. I was in pain. I wasn't always drinking. But there were times when I couldn't take it. And I was really struggling with how am I going to get by in life? And not taken seriously by doctors. And so, when I got the diagnosis, I cried with some relief, like, oh, good, I'll be able to do something. Reporter: How difficult was it to share it with your son? Not at all. I always want him to feel safe and never responsible for me, but he had already seen that I was falling and doing things. I have something called multiple sclerosis and he almost cried and said, will it kill you? And I said, no, I mean, we never know what kills us, Arthur, but this is not the doctor telling me I'm dying. And he was like, oh, okay. Reporter: What are doctors telling you? What's your prognosis? The doctor I saw, he said, within a year, I could have 90% of my abilities back, so, this is -- this is to say, let's meet again next year and see if I'm better. If I'm not, and I can still have a conversation, that's good enough. And I want to see. I want to see for other people and I want to see for me and see where I am. I was a little scared of talking and even my neurologist said, no, this will bring a lot of awareness, because no one has the energy to talk when they're in a flareup. But I do. Because I love a camera. Reporter: You got a date, I'll seal you in a year, okay? Okay. I can't wait. Reporter: Beautiful, beautiful. We can't wait for that interview a year from now. We are all pulling for Selma and everyone who is battling Ms in our country. And you can see much more of robin's interview later tonight only "Nightline." And "Vanity fair's" feature on Selma is live on their website. The March issue is out right now with Selma's story.
This transcript has been automatically generated and may not be 100% accurate.