Every week some 200 people will be diagnosed with multiple sclerosis (MS) in the U.S., according to Johns Hopkins University, and an overwhelming majority of those medical maladies will impact women. Back in 2021, actress Christina Applegate became one of them. For years she experienced subtle signs, such as losing her balance while shooting the pilot for Dead to Me in 2019, but things came to a head when numbness in her toes spread to her legs and eventually escalated into widespread pain.
Within a few months, she received a diagnosis of MS, an autoimmune disorder where the immune system attacks the myelin sheaths surrounding nerve fibers in the brain and spinal cord. These attacked areas form lesions that promote scarring and inflammation (known as sclerosis), and these lesions—as well as their location and temporal appearance—are key to diagnosing the disease.
Recently, Applegate revealed that she, in fact, didn’t have MS at all. The announcement came on MeSsy, an MS-focused podcast she co-hosts with fellow actress Jamie-Lynn Sigler, who was diagnosed with relapsing multiple sclerosis at the age of 20.
“There was some new technology that came out that was checking the brain MRIs, comparing them to other people,” Applegate said on the podcast, “and you’re not going to freaking believe this…she came into my room and said ‘congratulations, you don’t have MS.’”
Applegate explained that losing the diagnosis didn’t mean losing the symptoms, leaving her feeling like she was “back at square one.” She’s one of a shockingly large number of people who receive MS misdiagnoses every year. A study in 2019 found that roughly 18 percent of MS cases resulted in a misdiagnosis (though the results originated from a relatively small sample size). Another meta-analysis five years later refined that number to roughly 15 percent.
“Diagnosing MS is a little bit like putting a puzzle together,” National Multiple Sclerosis Society’s Bruce Bebo recently told Scientific American. “There’s not a single diagnostic test that tells you, ‘You have MS.’” Many other diseases, such as fibromyalgia, neuromyelitis optica, muscular dystrophy, Lou Gehrig’s disease, or even simple migraines, share similar symptoms with MS and need to be ruled out.
Historically, doctors have been more likely to dismiss the symptoms of women than those of men. In fact, before the arrival of magnetic resonance imaging in the 1970s, diagnosing MS based on symptoms alone led the medical profession to believe the disease was more prevalent in men (MS is in fact significantly more prevalent in women). It’s unknown whether such gender-based bias played a role in Applegate's own diagnosis. But there’s evidence that it still happens. Earlier this year, 26-year-old comedian Kylie Vincent experienced numbing symptoms indicative of MS, but her physician diagnosed them as a urinary tract infection.
Bias aside, doctors aren’t flying blind when diagnosing MS. Since 2001, they’ve relied on the McDonald Diagnostic Criteria, a standardized framework that has been refined several times over the decades. When the criteria debuted, an MS diagnosis could take as long as four years; now, thanks to advances in technology and testing—along with a 2024 update to the criteria—that timeline could shrink to just a few weeks or even days. One key breakthrough is a biomarker known as the “central vein sign”: a vein running straight through the center of a white matter lesion in the brain that serves as a telltale indicator of the disease.
“We think that it will take less time to reach a diagnosis after a patient has the first symptoms of MS,” Cleveland Clinic’s Daniel Ontaneda said in 2025. “And also, since we’re incorporating more specific tests, we believe that the diagnosis will really be more efficient. That is, we’ll have a small percentage of misdiagnoses.”
Here’s hoping that the pain and confusion of the misdiagnoses experienced by Applegate and thousands of other women will soon be a thing of the past.
Darren lives in Portland, has a cat, and writes/edits about sci-fi and how our world works. You can find his previous stuff at Gizmodo and Paste if you look hard enough.