Some people with stiff person syndrome have regained abilities, including walking on a treadmill, after receiving an experimental cell therapy, according to a multicentre trial published in JAMA Neurology on 9 November.

The early results offer a potential new research lead for a condition that affects singer Céline Dion. However, researchers say it is too soon to know whether the improvements will last.

Dion disclosed her diagnosis in 2022. She did not take part in the trial, and there is no suggestion that she has received CAR-T therapy. The treatment is more commonly used against cancer and remains experimental for stiff person syndrome.

The trial tested CAR-T therapy, which uses a patient's own immune cells. These cells are re-engineered to target the cells driving the disease before being returned to the body. Participants received a single treatment. Mayo Clinic, one of the three participating sites, said the results warrant further investigation in larger studies.

What Researchers Found in the CAR-T Trial

Dr Anastasia Zekeridou, a neurologist and researcher at Mayo Clinic in Rochester, Minnesota, said: 'What was most striking was the degree of improvement we saw in some patients. With existing treatments, we may be able to improve symptoms, but we very rarely see patients return to their previous level of function.'

She called the early results 'very encouraging' but said the key question was whether the improvements would be sustained.

Dr Sean Pittock, chair of Mayo Clinic's neurology department, said: 'There is still much we need to learn, but this opens an exciting new avenue for the field.' He said the findings could also have implications for other immune-mediated neurological conditions for which effective treatments are limited.

The trial was non-randomised. Mayo Clinic's release did not state how many patients took part or how long they were followed up, making it difficult to assess how widely the findings might apply. The therapy, mivocabtagene autoleucel, was developed by Kyverna Therapeutics, the trial's sponsor.

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One Participant's Experience, and the Limits of the Evidence

Shari St Germain developed severe leg cramps and difficulty walking in 2021. As her condition progressed, sudden noises could trigger muscle rigidity and falls. By 2024, standard treatments were no longer controlling her symptoms.

St Germain had once walked about seven miles a day. Mayo Clinic said she began noticing improvements months after receiving CAR-T therapy and later managed to walk on a treadmill again. Her experience is one person's account and does not establish how other patients might respond.

Stiff person syndrome causes progressive muscle stiffness and painful spasms, which can make walking, driving and working increasingly difficult. Sudden noises, touch and emotional distress can trigger episodes. The condition is estimated to affect one or two people in every million. Mayo Clinic first described the disease in 1956.

Dion has said stiff person syndrome affected her singing. In interviews in 2024, she described a treatment plan combining medication and immune therapy with physical and vocal therapy five days a week. Her experience has brought attention to the condition, but the trial provides no evidence about whether CAR-T therapy would be suitable for her.

Researchers have not described CAR-T as a cure, and the treatment is not ready for routine use in stiff person syndrome. It can cause serious side effects. Further evidence and longer follow-up are needed to establish who might benefit, what risks the treatment carries and whether the reported improvements endure.

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