Christina Applegate, the actress known for her advocacy on multiple sclerosis (MS), recently revealed that she had been misdiagnosed with the condition. Since first receiving the diagnosis in 2021, Applegate has been a vocal advocate for people living with MS, sharing her experiences on the podcast “Messy,” which she co-hosts with actress Jamie-Lynn Sigler, who has lived with the disease for more than two decades. However, new testing led her doctor to conclude that she does not, in fact, have MS.

Applegate disclosed the update on a recent episode of their show, describing the moment as emotional. She noted that her symptoms, which began about five years ago and included numbness and pain—common signs associated with MS—have not improved and, in some cases, have worsened. “I’m back at square one, that I don’t know what’s going on with me,” she said.

While a misdiagnosis of MS might seem uncommon, medical experts say it occurs more often than many realize. A meta-analysis compiling data from six studies estimated the misdiagnosis rate at approximately 15 percent. Specialists note that MS can be challenging to diagnose as there is no definitive blood test for the disease, which affects nearly one million individuals in the United States, predominantly women. Diagnosis typically requires evidence of clinical symptoms combined with characteristic lesions visible on magnetic resonance imaging (MRI) scans of the brain and spinal cord. When MRI findings are inconclusive, doctors often analyze spinal fluid and pursue other diagnostic avenues.

“The small print in diagnosing MS is you have to exclude everything else that is reasonable to exclude,” said Dr. Tanuja Chitnis, chief of the Neuroimmunology Division at Mass General Brigham Neuroscience Institute in Boston. She explained that conditions such as migraines, cerebrovascular disease, fibromyalgia, lupus, and other rare autoimmune or genetic disorders can produce symptoms similar to MS, making accurate diagnosis complex.

Misdiagnosed patients face not only unnecessary treatments but also delays in identifying the correct underlying condition. Dr. Michael Kornberg, an associate professor of neurology at Johns Hopkins Medicine, suggested Applegate’s public story could prompt others to reconsider their diagnoses. He also acknowledged the emotional toll involved in first having a definitive diagnosis and then having it revoked after years. “There is some comfort in just having a label and knowing what’s going on with your body. Living with that label for five years and then having it taken away is really distressing,” Kornberg said.