(CNN) — Christina Applegate is marking a milestone birthday after revealing her multiple sclerosis diagnosis in August.

Applegate celebrated her 50th birthday on Thanksgiving Day with a message for her fans on Twitter. “Yup. I turned 50 today. And I have MS. It’s been a hard one,” she wrote.

“Sending so much love to all of you this day,” Applegate continued. “Many are hurting today, and I am thinking of you. May we find that strength to lift our heads up. Mine currently is on my pillow. But I try.”

Yup. I turned 50 today. And I have MS. It’s been a hard one. Sending so much love to all of you this day. Many are hurting today, and I am thinking of you. May we find that strength to lift our heads up. Mine currently is on my pillow. But I try

— christina applegate (@1capplegate) November 26, 2021

Multiple sclerosis affects the central nervous system. It’s considered an autoimmune disease in which the immune system attacks its own healthy cells. It affects quality of life and can be disabling.

In her announcement earlier this year, the actor known for her roles in “Bad Moms,” “Married … with Children” and “Dead to Me” shared that it’s not been easy living with the disease.

“But I have been so supported by people that I know who also have this condition,” Applegate said. “It’s been a tough road. But as we all know, the road keeps going.”

There is no cure for multiple sclerosis — known as MS — but many people are able to manage their symptoms and adapt to new lifestyles after diagnosis.

Researchers believe that the disease is the result of both environmental and genetic factors, but the underlying cause is not known.