Symptoms That Mimic MS Prompt New Testing

Adults with fatigue, joint pain, or walking trouble may face several overlapping conditions before a diagnosis is settled.

Updated on Nov. 3, 2026 in Arthritis

Symptoms That Mimic MS Prompt New Testing

Actress Christina Applegate, 54, was told last month that she does not have multiple sclerosis, a diagnosis she had announced in August 2021. Doctors are now testing her for other conditions that can mimic MS, including lupus and Lyme disease, while she sees a rheumatologist about rheumatoid arthritis.

Why it matters

A revised diagnosis matters because conditions such as lupus and Lyme disease can produce symptoms that overlap with multiple sclerosis, so the same symptoms may point to different treatments. Applegate's symptoms have not improved despite the change, which is why testing is continuing one condition at a time.

This is a single patient's publicly shared account of a diagnostic revision and ongoing testing, not a clinical study. It describes a five-year period of symptoms believed to be MS, a revised diagnosis last month, and a fresh round of tests for conditions that mimic MS.

The players

Christina Applegate

American actress known for her television work, who has been a public advocate for people living with multiple sclerosis since announcing her diagnosis in 2021.

Jamie-Lynn Sigler

Actress who co-hosts the MeSsy podcast with Applegate and was herself a public voice about living with multiple sclerosis.

The details

Multiple sclerosis, lupus, Lyme disease, and rheumatoid arthritis can all produce fatigue, pain, and mobility problems that look similar on the surface. Doctors therefore test for each possibility separately to find the actual cause. Applegate is seeing a rheumatologist, a specialist in autoimmune and joint conditions, to investigate rheumatoid arthritis as a possible explanation.

August 2021: Applegate first announced a multiple sclerosis diagnosis.
Last month (October 2026): her doctor told her she does not have MS.
Late October 2026: she described needing a walker and about ten minutes to leave bed.
Tuesday, November 3, 2026: she discussed the fresh testing on her MeSsy podcast.

Health Landscape

Multiple sclerosis is frequently diagnosed only after other conditions with overlapping symptoms, such as lupus, Lyme disease, and rheumatoid arthritis, have been excluded. A revised diagnosis like this one illustrates how symptom-based diagnosis can change course as testing narrows the possibilities.

If you have had long-running symptoms such as fatigue, joint pain, or trouble walking, it is worth raising the full pattern with your doctor, since several conditions can look alike at first. Keeping a written record of when symptoms started and what makes them better or worse can help a clinician narrow the possibilities.

The takeaway

Several conditions can mimic multiple sclerosis, so a revised diagnosis is a reminder that testing continues until the cause is clear. Ask your physician which conditions have been ruled out and which tests remain.