Woman treated for MS for 18 years learns she had rare optic nerve disorder

DeMonica Amerson was diagnosed with multiple sclerosis in 2001, a label that stuck for nearly two decades before a specialist determined she actually had a rare autoimmune disease called neuromyelitis optica spectrum disorder, or NMOSD. The misdiagnosis meant she underwent daily shots and later monthly infusions to treat a condition her body did not possess.

Amerson, who is now 46, first noticed symptoms in her eyes shortly after graduating college. Doctors initially suspected optic neuritis or lupus before a spinal tap led to the MS diagnosis. She managed the disease through advocacy with the MS National Foundation, marriage, and a career as a school administrator, attributing periodic relapses to the progressive nature of the illness.

The error was caught in 2019 during a severe flare that left Amerson lethargic with numb legs. She missed her daughter's birthday party to go to the emergency room, where she experienced eye pressure and vomiting. An on-call neurologist performed a specialized blood test and later called to suggest she had a different rare autoimmune disorder.

Dr. Robert Bermel, director of the Mellen Center for MS at Cleveland Clinic, noted that large studies find between 15% and 20% of patients diagnosed with MS are eventually found to not have the condition. He explained that misdiagnoses often happen because abnormalities on brain scans are misinterpreted. New diagnostic criteria published in 2025 aim to reduce these errors, though the process still relies heavily on doctor interpretation.

Dr. Josef Gutman, director of NYU Langone's Long Island Comprehensive MS Care Center, said the wide spectrum of MS symptoms makes the condition difficult to isolate. "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," Gutman said. The diagnosis usually requires combining patient history, MRI imaging, and spinal fluid markers.

NMOSD affects the central nervous system, specifically the spinal cord and optic nerves. Dr. Mark Tullman, associate director of the White Plains Hospital MS Center, described the disease as causing similar symptoms to MS but often with greater severity. Unlike MS, which lacks a single diagnostic test, many people with NMOSD have a detectable antibody in their blood that can confirm the diagnosis when tested.

Amerson reacted with anger when she learned her previous diagnosis was wrong, describing the feeling of having to adjust after treating MS since age 21. She began a new infusion treatment called Uplizna, which she reported is working well, though she still manages fatigue and pain. She has since shifted her advocacy efforts toward raising awareness for NMOSD, hoping to inspire her two daughters and other leaders.

The case gained public attention earlier this month when actress Jennifer Applegate revealed on her podcast that she had been incorrectly diagnosed with MS for nearly five years. Applegate, who uses mobility aids, stated that doctors were causing her symptoms. Amerson expressed solidarity with Applegate, noting that going public about the diagnosis helps others understand the experience of living in the unknown.