Actor Christina Applegate announced on her podcast, MeSsy, that she was misdiagnosed with multiple sclerosis (MS) following years of treatment for the condition. Dr. Marwa Kaisey, a neurology professor at Cedars-Sinai Medical Center who appeared on the podcast, stated that nearly one in five people told they have MS do not actually have the disease. Applegate, who had been discussing her life with the condition alongside actor Jamie-Lynn Sigler, noted that her symptoms have persisted despite the corrected diagnosis.
Medical experts state that MS is difficult to identify because no single definitive test exists for the condition. The disease occurs when the immune system attacks the central nervous system, producing symptoms that vary significantly between individuals. Dr. Josef Gutman of NYU Langone’s Long Island Comprehensive MS Care Center explained that diagnosis requires a combination of patient history, magnetic resonance imaging (MRI), and markers such as spinal fluid analysis rather than a single blood test.
According to Dr. Robert Bermel, director of the Mellon Center for MS at Cleveland Clinic, misdiagnoses often occur when brain scan abnormalities are misinterpreted. While brain lesions are a primary indicator of MS, they can also be caused by migraines, smoking, or high blood pressure. When a misdiagnosis is identified, doctors typically investigate other potential causes for symptoms, such as fibromyalgia, thyroid disorders, sleep disorders, or other autoimmune conditions that cause inflammation and fatigue.
For the individual patient, a misdiagnosis can result in years of managing the wrong condition. A person would notice this change through a lack of improvement in their symptoms despite following MS treatment protocols. While Dr. Bermel stated that most common MS treatments are "very safe" and unlikely to endanger health, an incorrect diagnosis can delay the identification of the actual cause of a patient's illness. This "sidetracks" the medical process, as noted by Bermel, meaning patients might continue to experience debilitating symptoms, such as the mobility issues Applegate reported, without appropriate intervention for the true root cause.
The medical community has responded to these challenges by updating the diagnostic criteria for multiple sclerosis. In 2025, an international panel of experts published new guidelines intended to increase specificity, particularly regarding the interpretation of brain lesions. These new standards are designed to help specialists differentiate MS from "mimic" conditions like migraines or chronic pain syndromes. Moving forward, patients concerned about their status are encouraged to seek second opinions from MS specialists who have access to advanced MRI sequences and spinal fluid analysis to confirm or rule out the disease.