Sarah Chalke Talks Emotional 'Grey's Anatomy' Guest Appearance: 'It's Going to Save Kids'

The "Scrubs" alumna stars in a storyline based on her real-life battle with her son's illness.

On Thursday's "Grey's Anatomy," Sarah Chalke guest stars as a frantic, scared mother of a very sick little boy -- a role she knows all too well.

The storyline isn't just pulled from real life -- it's pulled from her own real life.

Two years ago, Chalke and fiancé Jamie Afifi were the frantic, scared parents of a 12-month-old son, Charlie, who was suffering from symptoms that kept getting misdiagnosed. Finally, doctors determined he had Kawasaki disease (KD), just in time; the confounding malady must be treated within a 10-day window or patients run the risk of developing heart disease. Charlie received treatment at 10 and a half days and is currently doing well, a relieved Chalke told Yahoo TV!. The causes of KD are still unknown. In a 2012 episode of "The Doctors," actress Kelly Preston revealed that her late son, Jett Travolta, had suffered from KD as a child and believed it was a contributing factor that led to his autism.

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On "Grey's," Chalke takes her boy to Grey-Sloan Memorial, where Meredith (Ellen Pompeo) and Jo (Camilla Luddington) race to figure out what's wrong with him.

We spoke with Chalke about why she decided to tell her story to Shonda Rhimes at "Grey's Anatomy" and why she hesitated over taking the part herself.

What pushed you to share such a personal story?

My son had KD two years ago, and it took me a long time to have the courage to speak about it. I spoke at the [KD "Save a Child's Heart"] fundraiser in November of this past year, and I heard all these other parents' stories. I had never met anyone who had had it before. They were all so brave, and the experience galvanized me to feel like we have to do something; we have to do whatever we can to raise awareness for this rare thing that there is a treatment for but that is so often misdiagnosed.

Then there was the idea to do an episode on a medical show. The next day, I talked to my agent and he had called Shonda at "Grey's." When I told them the story, they said, "We want to do a story about KD, and will you play the mom?" I said, "Thank you so much, I can't put into words how much it means to me that we're going to do this episode because it's going to raise awareness and it's going to save kids."

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I just needed a tiny minute to think about playing the mom, but I called back right after and said, "I would love to play the mom, yes please." Normally I'm excited to go to work and I love my job, but this was one that I had obviously some anticipation over, because I didn't know what it was going to be like to go back to that mindspace and to hold a baby that was made up to look like my son did at the time. It's a very visual disease; you get all these visual symptoms and high fevers, red bloodshot eyes and everything.

That must've been very difficult for you.

It was. As an actor, you think, "Am I going to be able to cry when I'm supposed to cry?" This was more like, "Am I going to be able to turn off the faucet when they yell 'cut'?" But I kept going back to, in my mind, why I'm doing this, which is this is going to save some kids and prevent some people [from] going through what we went through.

We had a really hard time getting Charlie diagnosed. There was this one website, KDFoundation.org, and it lists the symptoms so clearly. He got the treatment on Day 10 and a half, which is on the late side, and thank God he's OK. So the time [since] has allowed me to be able to come out and speak about it. It was a big decision, because when it's your kid, you just want to do everything you can to protect your privacy.

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But at the end of the day, sometimes life has other plans, and we just decided in the balance of things, because he's OK, we will be OK if we talk about this and raise awareness for it.

Was it very emotional on set? How did the other actors respond?

It was an emotional experience. Crew members and other actors were coming up to me throughout the shoot saying, "Oh I just heard that this was your experience," and people opened up to me about their experiences -- things that were difficult for them that happened to their kids or their friends. So, it was quite powerful.

I also love that the episode is called "Can't Fight This Feeling" [because] another thing I really wanted to do was to give the message to parents: Don't feel scared to get a second, third, fourth, fifth, sixth opinion or to advocate for your kid or to go back and ask more questions or go to the ER.

Chalke's "Grey's Anatomy" episode airs March 28 at 9 PM on ABC; her new sitcom "How to Live With Your Parents (For the Rest of Your Life)" debuts the following Wednesday, 4/3 at 9:30 PM.