Christina Applegate thought she had MS for 5 years. Now she's learned she was misdiagnosed — and her symptoms remain unexplained.

Christina Applegate was diagnosed with MS in 2021.

She recently learned she was misdiagnosed — and feels like she's "back to square one" with treatment.

Axelle/Bauer-Griffin/FilmMagic Christina Applegate recently learned that she was misdiagnosed with multiple sclerosis (MS).

Applegate was first diagnosed in 2021 after multiple tests and worsening symptoms.

About 15% of MS patients are believed to be misdiagnosed, given how complex the disorder is.

After being diagnosed with multiple sclerosis (MS) in 2021, living with severe symptoms, and becoming one of the most famous celebrities with the disorder, Christina Applegate learned some shocking news: She doesn't actually have MS.

In an October 20, two-part episode of her podcast "MeSsy" with Jamie Lynn Sigler (another actor diagnosed with MS), Applegate shared that she took over half a year off from recording the podcast to process the news of her MS misdiagnosis.

According to Applegate, her doctor framed the revelation as a positive update.

"She came into my room and said, 'Congratulations, you don't have MS,'" Applegate said in the podcast.

Jamie-Lynn Sigler, Applegate's co-host on the podcast, was diagnosed with relapsing multiple sclerosis when she was filming "The Sopranos." Paula Lobo/American Broadcasting Companies, Inc. via Getty Images But to Applegate, no longer having an explanation for the pain, balance issues, tremors, incontinence, and fatigue she'd been living with for years felt more like being "back at square one." "You don't get misdiagnosed and then all of a sudden, I'm better," she said.

"If anything, I've gotten worse, in some ways." Applegate's story is far from a medical anomaly.

MS researchers estimate that about 15% of worldwide MS patients are actually misdiagnosed, based on a 2024 meta-analysis of multiple studies.

Two researchers shared why MS is so challenging to diagnose — and why more people might end up with Applegate's experience in the future.

The race to diagnose a hard-to-diagnose disorder MRIs are important diagnostic tools for diagnosing MS, but researchers say they're just one piece of the puzzle.