Christina Applegate has revealed she’s been diagnosed with multiple sclerosis.

The 49-year-old actress revealed the recent diagnosis in a pair Twitter posts early Tuesday.

“Hi friends. A few months ago I was diagnosed with MS,” Applegate wrote. “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. Unless some a------ blocks it.”

She continued, “As one of my friends that has MS said ‘we wake up and take the indicated action’. And that’s what I do. So now I ask for privacy. As I go through this thing. Thank you xo.”

MS is a disease of the brain and spinal cord (or central nervous system), according to The Mayo Clinic.

There is no cure for multiple sclerosis, but there are treatments that can manage symptoms.

Applegate is also survivor of breast cancer. She was diagnosed in 2008 and had a prophylactic double mastectomy.

How common is MS?

It’s estimated that one million people in the U.S. are affected by MS and nearly 2.1 million people worldwide are affected.

What are the demographics?

According to the National Multiple Sclerosis Society, women are more likely to have MS, but men can get it too. Most people are diagnosed between the ages of 20 and 50, but children and older adults may develop the disease.

What is MS?

Dr. Jennifer Ashton said to think of it as "a neurologic condition affecting the central nervous system with an immune component. Imagine that our nerves are a hose and it needs that insulation to get the water from point A to point B. You can think of MS as lots of little holes ... so it leaks and it disrupts the passage of those messages, those signals in the central nervous system."

What are the symptoms?

Ashton said symptoms can run the gamut. "People can complain of a squeezing sensation in their torso, fatigue, weakness, difficulty walking, stiffness or muscle spasms, loss of balance," she said. "This can affect speech, it can affect vision. It can affect bladder function. This is a debilitating and often progressive neurologic condition so the symptoms really vary."

Ashton added that women are four times more likely to be diagnosed than men.

"This is a great example of how the same condition, MS, really presents differently based on gender," she said.

What are the treatments?

There are multiple ways MS can be managed, such as using steroids and therapies that target the immune system but it depends on factors including a patient's severity, disease stage, and medical history. "Treatment can be variable depending on the severity of disease, starting with steroids to help decrease the inappropriate immune response and can even involve plasma exchange," ABC News contributor Dr. Darien Sutton said.

What are the prognoses in general?

Symptoms may be temporary or permanent and can worsen overtime. In some cases it can lead to paralysis, but it varies case by case.