Kristen Johnston, former 3^rd Rock from the Sun star, posted on her Facebook page Tuesday, December 17, that she was diagnosed with lupus myelitis, a rare form of the lupus disease, according to the Hollywood Reporter.

Johnston who is currently starring in TV Land's The Exes, said she's "gonna be fine," although she missed to participate in the show's two episodes.

According to reports, Johnston was initially hesitant to divulge the name of disease she was diagnosed with. Instead, she explained that her recent health issues meant wouldn't be able to shoot in the upcoming episodes of her show, reported the Hollywood Reporter.

"I've been really, really sick since early Sept.," Johnston posted on her Facebook page. "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. Lying down I'm fine, which is great for writing or killing time on social media (thank you all!!), but it's kind of disasterous [sic] when you're in a sitcom that requires tons of physical comedy."

Johnston also explained that she did the best she could to be present in The Exes' shoot, but had to miss two episodes where guest star Leah Remini is appearing. Remini will play the role of Stuart's sister and her first episode will air on January 1, 2014. Johnston said that "Remini's so funny the audience won't even miss her."

According to Johnston's Facebook post, it took four months and 17 doctors, plus two weeks at the Mayo Clinic last November, before she was diagnosed with lupus myelitis.

"[That means] 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!" Johnston's Facebook page said.

Johnston didn't mention she's been diagnosed with lupus myelitis because she doesn't want people overreacting about her condition. She thanked the cast and crew of The Exes for being "so patient, understanding, loving & supportive."

"It's true that when you're sick, you find out who your real friends are, and these people, along with so many others, like ..... Oh Crap. This is starting to sound like a dreadful acceptance speech, so I'll just say you know who you are. Thank you & I love you," she wrote.