Christina Applegate has revealed that doctors are investigating several other medical conditions after she was told that her multiple sclerosis (MS) diagnosis was incorrect.
The 54-year-old actress, known for her roles in Dead to Me, Anchorman and Married... with Children, was originally diagnosed with MS in 2021.
Since then, she has spoken openly about the difficulties of living with debilitating symptoms, including problems with mobility and carrying out everyday activities.
However, in October 2026, Applegate revealed that she had been informed she did not have MS after all.
The news came as a shock to the actress, who explained that her symptoms had not disappeared despite the change in diagnosis.
Now, during the November 3 episode of her MeSsy podcast, Applegate has shared an update about the conditions her doctors are considering.
What does Christina Applegate think she might actually have?
Speaking to podcast guest Jack Osbourne, who has also publicly discussed living with MS, Applegate explained that she was undergoing further testing to identify the cause of her symptoms.
She revealed that doctors were investigating rheumatoid arthritis, lupus and Lyme disease, among other conditions that can sometimes produce symptoms resembling those of MS.
Applegate explained that the process involved gradually ruling out different illnesses rather than immediately arriving at a new diagnosis.
"We're going into square one, just doing some testing and going one by one of kind of the sister diseases to MS," she said.
She continued by naming rheumatoid arthritis, lupus and Lyme disease as conditions being considered.
However, the actress has not confirmed that she has any of these illnesses.
Her comments indicate that testing is ongoing and that doctors are still working to establish an explanation for her symptoms.
What is the subtle symptom these conditions can share?
One symptom that can appear across several of the conditions being investigated is persistent fatigue, which may be mistaken for ordinary tiredness or attributed to stress and a demanding lifestyle.
Fatigue can be particularly difficult to recognise because it is not always visible to other people and can occur alongside many different medical conditions.
In people with MS, fatigue can be severe and may interfere with concentration, mobility and everyday activities.
Rheumatoid arthritis and lupus can also cause significant fatigue because of the inflammation associated with these autoimmune conditions.
Lyme disease may cause tiredness alongside other symptoms, particularly during the early stages of infection.
However, fatigue is extremely common and is not, by itself, evidence of any of these conditions.
Applegate has not identified fatigue as the specific symptom that led her doctors to reconsider her diagnosis.
What is rheumatoid arthritis?
Rheumatoid arthritis is a long-term autoimmune condition in which the immune system mistakenly attacks tissues surrounding the joints.
According to the NHS, it commonly causes pain, swelling and stiffness, particularly in the hands, feet and wrists.
Some people also experience fatigue, reduced appetite and periods when symptoms become more severe.
Although rheumatoid arthritis primarily affects the joints, inflammation can sometimes affect other parts of the body.
There is currently no cure, but treatments can help control inflammation, relieve symptoms and reduce the risk of joint damage.
Because fatigue, discomfort and certain mobility difficulties can occur in both rheumatoid arthritis and MS, doctors may investigate both conditions when symptoms are unclear.
What is lupus and why can it resemble MS?
Lupus is another autoimmune condition in which the immune system attacks healthy tissues.
It can affect different parts of the body, including the joints, skin, kidneys and, in some cases, the nervous system.
The condition is sometimes described as a great imitator because its symptoms can resemble those of several other illnesses.
People with lupus may experience joint pain, fatigue, skin rashes and periods of increased disease activity known as flares.
When the nervous system is affected, lupus can occasionally cause neurological symptoms that overlap with those seen in MS.
However, lupus and MS are distinct conditions with different diagnostic criteria and treatment approaches.
Doctors typically use a combination of symptoms, physical examinations, blood tests and other investigations when assessing suspected lupus.
What is Lyme disease?
Lyme disease is a bacterial infection transmitted to humans through the bite of an infected tick.
Early symptoms can include fever, fatigue, muscle aches and headaches.
Some people develop a distinctive expanding rash around the bite, although not everyone experiences this symptom.
If left untreated, the infection can sometimes affect the nervous system, causing symptoms such as numbness, weakness or nerve pain.
These neurological complications can occasionally resemble symptoms associated with MS.
Unlike MS, Lyme disease is caused by bacteria and is treated with antibiotics.
Most people recover well when the infection is identified and treated promptly.
There is no confirmation that Applegate has Lyme disease, and her doctors are still investigating possible explanations.
What did Christina Applegate say about being misdiagnosed?
Applegate first revealed the change in her diagnosis during the October 20 episode of MeSsy, following a seven-month break from the podcast.
She recalled being told by a medical professional that she did not have MS, describing the news as emotionally complicated rather than immediately reassuring.
Although others reacted positively, Applegate explained that the announcement did not change the physical difficulties she continued to experience.
She said: "You don't get misdiagnosed and then all of a sudden I'm better."
The actress explained that her symptoms had continued and that she was struggling to understand what had been happening to her body since 2021.
She also described how difficult it was to separate her identity from a diagnosis that had shaped her life for years.
During her November 3 podcast appearance, she said she was open to advice and treatment options that might help her feel better.
How has Christina Applegate's health affected her daily life?
Applegate has previously spoken about how significantly her symptoms have affected her independence and career.
She explained that she still needs to use a wheelchair for some medical appointments because walking even relatively short distances can be difficult.
The actress also described the emotional toll of losing the ability to work in the same way she once did.
For several years, she believed MS explained those limitations and gave her a framework for understanding her experiences.
Discovering that the diagnosis was incorrect has left her facing renewed uncertainty.
She has also expressed concern about disappointing people who looked to her as an advocate for those living with MS, although her experiences of illness and disability remain real regardless of the eventual diagnosis.
What happens next for Christina Applegate?
Applegate has said that her medical team is continuing to investigate conditions that can produce symptoms similar to MS.
The process may involve blood tests, neurological assessments and other investigations depending on what her doctors consider clinically appropriate.
At present, there is no publicly confirmed replacement diagnosis.
While rheumatoid arthritis, lupus and Lyme disease are among the possibilities being explored, none has been established as the cause of her symptoms.
Applegate has continued using her podcast to speak openly about the emotional and physical impact of living with an unexplained illness.
Her latest update highlights the complexity of diagnosing conditions with overlapping symptoms and the importance of further medical investigation when an existing diagnosis is called into question.
For now, the actress remains focused on finding answers and identifying whether any additional treatment could improve her quality of life.
