Actress Selma Blair, who has multiple sclerosis, has dropped out of Dancing With the Stars at her doctors' guidance four weeks after she joined the competition.

Blair revealed her diagnosis of having MS in 2018 and spoke of her journey with the disease on the show.

"I was sick for so many years," she said. "I was searching and searching for how to help myself ... so to get the diagnosis in 2018 of MS was a huge relief. It was the beginning of recovery as a person."

The actress, known for roles in Legally Blonde and the Hellboy franchise, broke the news on Monday's episode. "I can't go in with the competition," she said. "I pushed as far as I could. With a chronic illness, you do have special considerations and my body is definitely taking a hit. It's way too much for the safety of my bones."

What is multiple sclerosis?

Multiple sclerosis, also known as MS, happens when the body's immune system attacks the central nervous system, which includes the brain and spinal cord and optic nerves. As a result, the myelin, a fatty substance that serves as a protective layer for nerve fibers, is damaged and it becomes more difficult for messages to reach the central nervous system.

Some symptoms of MS include weakness, fatigue, difficulty walking and seeing, chronic pain and muscle spasms, according to the National Multiple Sclerosis Society.

What causes it?

It is not clear how MS develops, though it may be a combination of genetics and other risk factors, such as sex, race, age, smoking habits and certain infections, according to the Mayo Clinic.

How is it treated?

There is no cure for MS. During a flare-up of MS symptoms, doctors may administer steroids to reduce inflammation, or prescribe physical therapy. Preventative approaches may include injections of proteins.

Various specialists, such as speech doctors, neurologists and physiologists may be involved in treatment plans.

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