Up to 20% of MS diagnoses may be wrong, like Christina Applegate's

Actor Christina Applegate announced Tuesday that she had been misdiagnosed with multiple sclerosis after years of believing she had the condition — and experts say her experience is more common than many people realize.

Applegate shared the news on her podcast, MeSsy, where she and actor Jamie-Lynn Sigler discuss life with MS. In a follow-up episode, Dr. Marwa Kaisey, an associate professor at the Cedars-Sinai Medical Center department of neurology, said that almost 1 in 5 people who are told they have multiple sclerosis "didn't actually have it."  

There is no single test to confirm MS, a disease where the body's immune system attacks the central nervous system. Symptoms vary from person to person and it can progress in different ways, according to the National Multiple Sclerosis Society. 

How can an MS misdiagnosis be discovered?

CBS News spoke with Dr. Robert Brumel, the director of the Mellon Center for MS at Cleveland Clinic, a multidisciplinary center that cares for more than 11,000 patients with multiple sclerosis, about the risk of an MS misdiagnosis and what patients need to know. 

He said a misdiagnosis is most often found when a person seeks out a second opinion because their symptoms aren't getting better. This doesn't always mean the diagnosis is wrong, but can be an indicator for more advanced tests. (Brumel said most MS treatments, especially the ones most commonly used, are "very safe" and wouldn't put a person's health in danger.) 

When a misdiagnosis happens, the root cause is typically that abnormalities on brain scans were misinterpreted, Brumel said. Lesions on the brain are considered a hallmark of MS, but they can also be caused by other medical issues such as high blood pressure, smoking or migraines. More advanced MRI sequences can help differentiate between MS lesions and those caused by other conditions, Brumel said. 

When concerns about a potential misdiagnosis arise, the next steps typically involve running specialized tests. Those can include advanced MRI sequences to study the lesions more closely, a spinal MRI, or spinal fluid analysis that can identify specific abnormal immune proteins, Brumel said. 

How common is an MS misdiagnosis? 

On MeSsy, Kaisey described MS misdiagnoses as "fairly common." Brumel said that the largest studies looking at the risk of misdiagnosis have shown that between 15% and 20% of patients diagnosed with MS are found to not actually have the condition. 

Dr. Josef Gutman, the director of NYU Langone's Long Island Comprehensive MS Care Center, told CBS News that the wide spectrum of symptoms that can be attributed to multiple sclerosis makes the condition difficult to diagnosis. 

"It'si mportant to keep in mind that those symptoms are not necessarily specific in a lot of ways. It's sort of the story, combined with MRI imaging, combined with other markers like spinal fluid, that help us make the MS diagnosis," Gutman said. "It's not like diabetes, where there's one blood test and if it's above this number, it's diabetes, if it's below this number, it isn't. There's a lot of things going into the diagnosis." 

New multiple sclerosis diagnostic criteria, developed by an international panel of experts in the field, were published in 2025 to try to reduce this risk. These criteria are more specific than before, according to Brumel, especially when it comes to interpreting brain lesions. 

"We really place a high premium on getting the diagnosis correct from the start, so that then we can move very confidently into highly effective therapy for MS," Brumel said. 

What happens after an MS misdiagnosis? 

If a patient's multiple sclerosis misdiagnosis is identified, doctors will then start looking at other potential causes for their symptoms, Brumel said. 

They may be suffering from an autoimmune condition, which can cause joint pain, swelling and system-wide inflammation. Fibromyalgia is a "commonly identified diagnosis that mimics MS," Brumel said. Migraines are also a possible diagnosis, because migraine can cause lesions and other neurological symptoms. Chronic pain or fatigue syndromes can also "masquerade as MS," Brumel said. 

Sometimes, a person may not have one disorder but several, Brumel said, noting that an incorrect diagnosis "really sidetracks things."

"MS can sometimes be a gratifying solution to a patient with many symptoms because it's thought of as kind of a single, solitary root cause of things," he said, adding that he has seen patients whose fatigue is caused by a sleep or thyroid disorder, while rheumatoid conditions or fibromyalgia cause pain and swelling. 

On her podcast, Applegate said learning she had the wrong diagnosis has made things harder for now, since there's still no explanation for the debilitating symptoms that affect her daily life and mobility. 

"You don't get misdiagnosed and then all of the sudden I'm better," Applegate said. "If anything, I've gotten worse. So I'm back at square one where I don't know what's going on with me. And that's going to be an online investigation that my doctors are going to be getting into just to find out what has been going on since 2021, why did this happen?"

When to seek out a second opinion 

While only a minority of patients are misdiagnosed, anyone concerned about their diagnosis should always feel comfortable seeking a second opinion, Brumel said. Even when the original diagnosis is correct, a second opinion can help a patient find other resources, he noted.

"MS is a life-changing diagnosis, and anytime somebody is facing something like that, I always think a second opinion is potentially in order," Brumel said. 

Patients can also seek out a multiple sclerosis expert, Brumel said. The National Multiple Sclerosis Society maintains an online registry and map of care centers and MS specialists nationwide. Brumel called that list a "really good starting point to identify" nearby resources. 

MS specialists are likely to be up to date on diagnostic criteria, Gutman said. They are also more likely to be familiar with conditions that mimic multiple sclerosis, and have access to the more specific tests that can help confirm a diagnosis.