Stiff person syndrome — a rare, progressive disorder that causes painful muscle spasms — can be treated with a therapy commonly used for cancer, a new case report suggests.
IN rigid person syndrome (SPS), the immune system attacks a key protein in the nervous system. The condition is rare, it affects less than 5000 people in the US, but recently gained attention when Canadian singer Céline Dion has announced she had SPS.
Those most severely affected by SPS develop progressively worse muscle stiffness, eventually leaving them bedridden, while chest spasms can sometimes impede their breathing. There is currently no cure for SPS, only treatments to manage the symptoms – but these not always help.
Now, a case study published in June in the journal PNAS highlights a possible new treatment for people with SPS.
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One of the biggest challenges people with SPS face is getting a diagnosis, because the disease is rare and its symptoms resemble those of other disorders. in 2014, Dr. Simon Faissner, a neurologist at St. Josef at the Ruhr University of Bochum, met the patient presented in the case report. She reported stiffness and pain when moving, but her case notes said previous doctors thought her symptoms were psychosomatic – caused by a psychological condition.
Faissner performed a lumbar puncture test, revealing that the patient’s cerebrospinal fluid, which circulates through the spinal cord and brain, was filled with antibodies against a protein called glutamic acid decarboxylase (GAD). GAD is needed to make GABA, a chemical messenger that helps reduces the activity of neurons. Without it, the brain sends signals at an excessive rate, leading to the muscle spasms and stiffness seen in SPS.
After her diagnosis, the patient began therapies that lowered these GAD-targeting antibodies and stabilized her condition for several years. However, by 2023, her condition had worsened, leaving her unable to walk for some time.
To try and alleviate some of the patient’s symptoms, Faissner and Dr Jeremias Motteanother neurologist at St. Josef, decided to use a new treatment: an adapted one CAR T cell therapy.
This treatment uses immune cells called T cells, which hunt down and kill abnormal and diseased cells in the body. The therapy involves removing some of a patient’s T cells and adjusting them to target a specific target – usually cancer.
However, in the new case report, the researchers targeted the CAR T cell junctions on antibody-producing immune cells, called B cells. This approach has previously been tried as a treatment for an autoimmune condition called lupus nephritisbut Faissner and Motte wanted to see if it could help their SPS patient.
Existing SPS therapies also target B cells, but less completely. “It’s not such a profound depletion of B cells,” Motte told Live Science. “Not as deep in the lymph nodes and not as deep in the organs, muscles or bone marrow.”
The idea is that CAR T-cell therapy eliminates the B cells that drive the disease, but leaves behind a population of “baby B cells,” Motte said. These then repopulate the body without creating harmful antibodies.
“It’s like rebooting a computer system,” Faissner told Live Science. “The problematic immunological system must be erased [following the therapy].”
The treatment had a rapid effect, the team found in the case report. The patient had recovered some ability to walk before receiving the therapy, and within six months of a single treatment, her walking speed had doubled. She was still tired and stiff, but went from walking just a few yards to about 4 miles (6 kilometers) a day.
The patient was also able to discontinue all other immunotherapies and reduce the use of benzodiazepines, which help compensate for lost GABA function.
“It’s an impressive improvement,” Marinos Dalakasa neurologist at Thomas Jefferson University who developed one of the first immunotherapies for SPS in 2001, told Live Science.
Dalakas, who was not involved in the case, stressed that the new treatment remains experimental. Future trials will need to expand on the limited data provided by a single case study. He also noted that there is a mid-stage clinical trial of a different one CAR T-cell therapy for SPS occursalthough it will take some time before there are any results.
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