Actress, Christina Applegate, revealed Tuesday that she's been diagnosed with multiple sclerosis.

According to CNN, the 49-year-old star shared the news with fans on Twitter, saying, "It's been a strange journey. But I have been so supported by people that I know who also have this condition. It's been a tough road. But as we all know, the road keeps going..."

Multiple sclerosis, or MS, is often described as an autoimmune disease caused by the immune system's attack of its own healthy cells. It can potentially disable the brain and spinal cord (the central nervous system) and limit quality of life.

That said, many people with MS are able to manage their symptoms with the assistance of a neurologist. 

Applegate said she was diagnosed a few months ago.

This isn't her first encounter with a severe health concern. 

In 2008, at 36 years old, Applegate was diagnosed with breast cancer. At the time, doctors provided her with two options, to either undergo radiation treatment and then be tested regularly for the rest of her life or have both of her breasts surgically removed.

Applegate chose to undergo a double mastectomy.

After a successful surgery, Applegate was interviewed by Oprah Winfrey and said she's grateful for the new perspective the challenge left her with.

"[There's] this need and this desire to make every single day count," the actress said. "I used to say... 'Don't sweat the small stuff -- not even the big stuff.' At the end of the day, none of it matters but your own joy, your own spiritual journey that you go on, God, your loved ones, your friends, your animals. These are the things you've got to cherish and love and embrace."

Since the 2008 surgery, Applegate remarried, had a child, and went on to star in a number of television shows and films.

She is widely known for her roles in 'Bad Moms,' 'Married... with Children,' and 'Dead to Me.'