Fibromyalgia – a poorly understood condition that causes widespread pain throughout the body and extreme tiredness – may be caused by be an autoimmune response that increases the activity of pain-sensing nerves throughout the body.
The findings, published in the Journal of Clinical Investigation, challenge the widely held view that the condition originates in the brain, and could pave the way for more effective treatments for the millions of people affected.
They could also have implications for patients suffering from myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) and “long Covid”. “These different syndromes are symptomatically very similar, so I think it could be very relevant to both of these conditions,” said Dr David Andersson from the Institute of Psychiatry, Psychology and Neuroscience at King’s College London, who led the new study.
Fibromyalgia affects at least 1 in 40 people worldwide, although some estimates suggest nearly 1 in 20 people may be affected to some degree. It is characterised by widespread pain and crippling fatigue – often referred to as “fibro fog” – and usually develops between the ages of 25 and 55, although children can also get it. Similar to many autoimmune conditions, the vast majority of those affected (80% are women).
Current treatment tends to focus on gentle aerobic exercise, as well as drug and psychological therapies designed to manage pain. However, these have proven ineffective in most patients and have left behind an enormous unmet clinical need, said Andersson. “The widespread paradigm at the moment is that this is a disease that emanates from the brain, and I think our findings suggest that that’s not the case,” he said.
The development of new therapies has also been hampered by a limited scientific understanding of what causes the condition in the first place, but this could change with the discovery that the immune system is involved.
Andersson and his colleagues harvested blood from 44 people with fibromyalgia and injected purified antibodies from each of them into different mice. The mice rapidly became more sensitive to pressure and cold, and displayed reduced grip strength in their paws. Animals injected with antibodies from healthy people were unaffected.
Prof Camilla Svensson from the Karolinska Institute in Sweden, who was also involved in the study, said: “Antibodies from people with fibromyalgia living in two different countries, the UK and Sweden, gave similar results, which adds enormous strength to our findings.”
The mice recovered once the antibodies had been cleared from their systems, which took a few weeks. This suggests that therapies such as plasma-exchange, which are designed to reduce antibody levels and are available for other autoimmune disorders, such as myasthenia gravis, may be effective in fibromyalgia patients.
“Establishing that fibromyalgia is an autoimmune disorder will transform how we view the condition and should pave the way for more effective treatments for the millions of people affected,” Andersson said. “Our work has uncovered a whole new area of therapeutic options and should give real hope to fibromyalgia patients.
The next step will be to identify what factors the symptom-inducing antibodies bind to, said Svensson: “This will help us not only in terms of developing novel treatment strategies for fibromyalgia, but also of blood-based tests for diagnosis, which are missing today.”
Anderson said he also hoped to conduct similar experiments using antibodies harvested from people with ME/CFS and long Covid.
Des Quinn, the chair of Fibromyalgia Action UK, said: “The prospect of fibromyalgia being an autoimmune condition has been debated many times and this will add to that discussion. If these results can be replicated and expanded upon, then the prospect of a new treatment for people with fibromyalgia would be extraordinary. However, the results need further confirmation and investigation before the outcomes can be applied universally.”
It would also be interesting to investigate how these findings relate to other symptoms of fibromyalgia, such as fatigue, sleep disturbance, and cognitive issues, he added.