Kristen Johnson, who currently stars on TV Land’s The Exes and also starred on 3rd Rock From The Sun, told her fans on Facebook this week that she has been diagnosed with lupus, an auto-immune disease, which has kept her from filming.

In a post on Facebook Tuesday, Johnson said that she had been holding off on going public with her battle, but finally decided to let her fans know. She said that she has been “really, really sick” since early September, adding, “Full body muscle weakness to the extent that just walking difficult, stairs impossible and I even need a neck brace to hold my head up.”

She is fine while lying down, “but it's kind of [disastrous] when you're in a sitcom that requires tons of physical comedy.”

According to Entertainment Weekly, Johnson was at the Mayo Clinic during a break from The Exes for two weeks of treatments.

“This is how, after 4 months & 17 Drs (no lie) I've FINALLY been diagnosed with a rare auto-immune disorder,” she later wrote. “Meaning my immune system has decided to go rogue & attack my muscles. The good news: I'm finally on the right treatment, feeling better & back at work!”

Johnson added that Leah Remini has recently joined The Exes, so that will make up for her absence in a couple of episodes. She did appear in this week’s Christmas episode, which she urged all her fans to watch.

The actress played Sally Solomon on 3rd Rock from the Sun and Lexi Featherston on sex and the City.

image: NBCUniversal