Like Christina Applegate, I have MS. From my experience, I know looking healthy doesn't always mean feeling healthy.

The author first felt symptoms of multiple sclerosis at age 21.

Courtesy of Lindsay Karp Like Christina Applegate, I, too, have multiple sclerosis.

She looked radiant in a recent video.

For many with chronic illness, looks can be deceiving.

In my experience, you can look healthy while struggling with symptoms inside.

I remember the morning just after my 21 st birthday when pain first began shooting down my once healthy legs.

Soon, fatigue settled into every cell in my body, and walking, which was once routine, grew burdensome.

Muscle twitches flickered in every part of me, sparking a fear I'd never known previously.

My body felt foreign and broken, but on the outside, looking in the mirror, I was still me.

Symptoms of multiple sclerosis (MS) were festering from within; my appearance told a lie that confused everyone.

On Monday, Christina Applegate shared a video to Instagram announcing her release from a monthslong hospital stay for complications of her MS.

Acknowledging a mark on her cheek, she showed off her new hair color and a body that appeared fit and strong.

Christina smiled in the video, joy exuding from her, but it likely told only half of her story.

The other half — how she feels physically — remains elusive, only understood by those who live with chronic illness.