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  • Is Fibromyalgia an Autoimmune Disease?

    What Current Research Actually Shows

    Fibromyalgia is one of the most misunderstood chronic illnesses in modern medicine. It affects millions of people worldwide and is characterized by widespread musculoskeletal pain, fatigue, sleep disturbances, and cognitive difficulties often referred to as “fibro fog.” Despite its prevalence, the underlying cause of fibromyalgia remains an ongoing subject of research and debate.
    For decades, fibromyalgia has been classified as a nociplastic pain condition, meaning the pain originates from altered processing in the nervous system rather than tissue damage or inflammation. However, emerging research over the past several years has raised an important question: Could immune system dysfunction play a role in fibromyalgia?
    Recent studies in rheumatology, neurology, and chronic pain research suggest that immune abnormalities, including autoantibodies and inflammatory signaling, may contribute to fibromyalgia symptoms in at least some patients. At the same time, evidence remains mixed, and fibromyalgia is not currently classified as an autoimmune disease.

    Understanding where the science stands today requires examining both the evidence supporting an immune connection and the limitations of current research.
    The Traditional Understanding of Fibromyalgia
    Historically, fibromyalgia has been viewed primarily as a disorder of central sensitization. Central sensitization refers to a condition in which the brain and spinal cord amplify pain signals, causing the body to perceive normal sensations as painful. This altered pain processing can lead to the widespread pain and tenderness commonly experienced by fibromyalgia patients.
    The International Association for the Study of Pain classifies fibromyalgia under nociplastic pain, which occurs when the nervous system processes pain abnormally despite the absence of tissue damage or nerve injury (Paroli, Gioia, Accapezzato, & Caccavale, 2024).


    Research supporting this model includes neuroimaging studies showing increased activity in brain regions responsible for pain processing, as well as abnormalities in neurotransmitters such as serotonin and norepinephrine. These findings have helped shape current treatment approaches, which often focus on medications that affect nervous system signaling and therapies aimed at reducing central pain amplification.
    However, the central sensitization model does not fully explain all aspects of fibromyalgia. Many patients report symptoms that extend beyond pain processing, including immune-related symptoms, persistent fatigue, and overlap with other inflammatory conditions. These observations have prompted researchers to investigate whether additional biological mechanisms may be involved.


    New Evidence Linking Fibromyalgia and the Immune System


    In recent years, several studies have begun exploring whether immune system activity could contribute to fibromyalgia symptoms. While this research is still developing, some findings have been particularly significant.


    Autoantibodies and Pain Signaling


    One of the most notable discoveries involves the role of immunoglobulin G (IgG) antibodies. Antibodies are proteins produced by the immune system to identify and neutralize pathogens such as bacteria and viruses. In autoimmune diseases, antibodies mistakenly target the body’s own tissues.

    A 2023 study published in the journal Pain investigated whether antibodies from fibromyalgia patients could influence pain signaling. Researchers isolated IgG antibodies from individuals diagnosed with fibromyalgia and transferred them into mice. The results were striking: mice that received fibromyalgia antibodies developed increased pain sensitivity and nerve hypersensitivity (Krock, Morado-Urbina, Menezes, Hunt, Sandström, Kadetoff, Tour, Verma, & Kultima, 2023).


    Further analysis revealed that these antibodies bound to satellite glial cells, which are supportive cells surrounding sensory neurons in the dorsal root ganglia. These cells play an important role in regulating pain signals transmitted from the body to the brain.


    In addition, the study found that patients with higher levels of these antibodies experienced more severe fibromyalgia symptoms, including greater pain intensity and pressure sensitivity (Krock et al., 2023). This finding suggests that immune activity may influence symptom severity in some individuals.
    While this does not prove that fibromyalgia is an autoimmune disease, it provides compelling evidence that immune system factors may contribute to pain mechanisms.
    Altered Autoantibody Patterns in Fibromyalgia
    Other studies have also examined the presence of autoantibodies in fibromyalgia patients. A pilot study investigating autoantibody signatures found differences in immune markers between individuals with fibromyalgia and healthy control participants (Ryabkova, Churilov, & Shoenfeld, 2023).


    Researchers observed alterations in antibodies associated with neural signaling pathways, including those affecting gamma-aminobutyric acid (GABA) receptors. Because GABA plays a key role in regulating nervous system activity, abnormalities in these antibodies could potentially influence pain perception and neurological symptoms.
    The study also noted that some fibromyalgia patients showed antibodies targeting spinal ganglia, structures involved in transmitting pain signals from the peripheral nervous system to the brain. However, these antibodies were present only in a subset of patients, highlighting the complexity and heterogeneity of the condition.
    Immune Cells and Chronic Pain
    Beyond antibodies, several immune cell types have been implicated in fibromyalgia.
    Recent research has explored the role of mast cells, neutrophils, and microglia in the development of chronic pain.

    Mast cells are immune cells involved in inflammatory responses and allergic reactions. Studies have found increased mast cell numbers in skin biopsies from fibromyalgia patients, suggesting they may contribute to inflammatory signaling in pain pathways (Paroli et al., 2024).
    Neutrophils, another type of immune cell, have also been investigated. Experimental studies have shown that transferring neutrophils from fibromyalgia patients into animal models can induce widespread pain sensitivity.

    This suggests that immune cells themselves may influence pain amplification mechanisms.
    Within the central nervous system, microglia activation has been observed in several chronic pain conditions, including fibromyalgia. Microglia are immune cells that reside in the brain and spinal cord and release inflammatory cytokines when activated. Increased microglial activity has been associated with chronic widespread pain and may contribute to neuroinflammation.
    These findings suggest that fibromyalgia may involve a complex interaction between the nervous system and immune system rather than being solely a neurological condition.


    Fibromyalgia and Autoimmune Diseases
    Another area of research focuses on the relationship between fibromyalgia and established autoimmune disorders.


    Fibromyalgia frequently occurs alongside immune-mediated rheumatic diseases, including rheumatoid arthritis, Sjögren’s syndrome, psoriatic arthritis, and spondyloarthritis. Research suggests that fibromyalgia symptoms occur in a significant percentage of patients with these conditions (Mettler, Ming-Azevedo, & Hügle, 2025).
    Meta-analyses indicate that fibromyalgia occurs in approximately:
    21% of patients with rheumatoid arthritis
    13% of patients with axial spondyloarthritis
    18% of patients with psoriatic arthritis
    (Paroli et al., 2024).


    These rates are significantly higher than fibromyalgia prevalence in the general population. This overlap raises the possibility that shared biological pathways may contribute to both conditions.
    However, fibromyalgia symptoms in autoimmune diseases are often related to central pain sensitization rather than active autoimmune inflammation. As a result, the presence of fibromyalgia in autoimmune patients does not necessarily mean fibromyalgia itself is autoimmune.
    Why Fibromyalgia Is Not Classified as an Autoimmune Disease
    Despite emerging evidence linking immune activity to fibromyalgia, the condition is not currently classified as an autoimmune disease. Several reasons explain this.


    First, autoimmune diseases typically involve consistent immune attacks on specific tissues or organs. For example, rheumatoid arthritis targets joint tissue, and multiple sclerosis affects the central nervous system. In fibromyalgia, researchers have not identified a consistent tissue target for immune attack.


    Second, many fibromyalgia patients do not show abnormal autoimmune markers such as antinuclear antibodies. Studies examining these markers often find levels comparable to those seen in the general population (Ryabkova et al., 2023).


    Third, the strongest evidence supporting fibromyalgia still centers on central nervous system pain processing abnormalities. Neuroimaging studies repeatedly demonstrate altered pain processing in the brain, which remains the primary explanation for fibromyalgia symptoms.


    Finally, immune-related findings appear to apply only to a subset of patients, rather than representing a universal feature of the disease.
    What the Current Research Suggests
    Taken together, current evidence suggests that fibromyalgia likely involves multiple biological mechanisms.
    Central nervous system sensitization remains the primary driver of widespread pain. However, immune system abnormalities may contribute to symptom development in some individuals.

    Autoantibodies targeting satellite glial cells, altered immune signaling, and increased inflammatory activity all suggest that immune processes may influence pain pathways.
    Rather than replacing the nociplastic pain model, these findings suggest that fibromyalgia may involve a combination of neurological and immune factors.


    Future research will likely focus on identifying biomarkers that can distinguish different fibromyalgia subtypes. This could eventually lead to more personalized treatment approaches that target specific biological pathways.


    Conclusion


    Fibromyalgia remains a complex and multifaceted chronic illness. While it is still classified as a nociplastic pain disorder, recent research suggests that immune system activity may play a role in symptom development for some patients.


    Studies involving antibody transfer experiments, altered immune markers, and increased inflammatory signaling all point toward possible immune involvement. At the same time, the current evidence does not support classifying fibromyalgia as a primary autoimmune disease.
    Instead, fibromyalgia likely reflects an interaction between nervous system dysfunction and immune system activity, highlighting the need for continued research.
    Understanding these mechanisms is critical not only for improving treatment strategies but also for shifting the broader conversation about fibromyalgia toward a more accurate, biology-based understanding of the condition.


    References


    Krock, E., Morado-Urbina, C. E., Menezes, J., Hunt, M. A., Sandström, A., Kadetoff, D., Tour, J., Verma, V., & Kultima, K. (2023). Fibromyalgia patients with elevated levels of anti-satellite glia cell immunoglobulin G antibodies present with more severe symptoms. Pain, 164(8), 1828–1840. https://doi.org/10.1097/j.pain.0000000000002881⁠.


    Mettler, J., Ming-Azevedo, P., & Hügle, T. (2025). Fibromyalgia with concomitant immune-mediated rheumatic diseases: An evaluation of clinical characteristics, diagnostic criteria and multimodal treatment outcomes. Advances in Rheumatology, 65(27). https://doi.org/10.1186/s42358-025-00457-4⁠.


    Paroli, M., Gioia, C., Accapezzato, D., & Caccavale, R. (2024). Inflammation, autoimmunity, and infection in fibromyalgia: A narrative review. International Journal of Molecular Sciences, 25(11), 5922. https://doi.org/10.3390/ijms25115922⁠.


    Ryabkova, V. A., Churilov, L. P., & Shoenfeld, Y. (2023). Autoantibody correlation signatures in fibromyalgia and myalgic encephalomyelitis/chronic fatigue syndrome: Association with symptom severity. Autoimmunity Reviews, 22, 103364.

  • Central Sensitization Explained: Why the Nervous System Amplifies Pain in Fibromyalgia

    When Tests Are Normal but the Pain Is Not.


    Many people with fibromyalgia hear the same confusing message from doctors: your tests are normal.
    Bloodwork looks fine. Imaging shows nothing unusual. Yet the pain is persistent, widespread, and often severe.
    This disconnect has led to decades of misunderstanding about fibromyalgia. But research in pain neuroscience has begun to clarify what is happening.
    The issue is often not in the muscles or joints.
    The issue is how the nervous system processes pain.


    Researchers refer to this phenomenon as central sensitization—a biological process in which the brain and spinal cord become overly responsive to sensory signals.
    Instead of filtering incoming information, the nervous system amplifies it. Signals that should feel mild begin to feel painful, and existing pain signals become stronger.
    Central sensitization helps explain why fibromyalgia pain can be widespread, persistent, and difficult to treat with traditional pain medications.


    What Is Central Sensitization?
    Central sensitization refers to increased responsiveness of neurons within the central nervous system, particularly in the spinal cord and brain regions involved in pain processing (Jo Nijs, Lotte Lahousse, Efthymios Kapreli, Panagiota Bilika, İbrahim Saraçoğlu, Anneleen Malfliet, Iris Coppieters, and Mira Meeus, 2021).
    Under normal conditions, the nervous system filters sensory information. Signals travel from peripheral nerves through the spinal cord to the brain, where they are interpreted.
    When central sensitization develops, that filtering system becomes disrupted.
    The nervous system essentially turns up the volume on incoming signals.


    Two common features of this process include:
    Hyperalgesia – an exaggerated response to painful stimuli
    Allodynia – pain triggered by sensations that normally would not cause pain, such as light touch or mild pressure
    For someone living with fibromyalgia, something as simple as clothing pressing against the skin or sitting for too long can trigger pain.
    How Central Sensitization Changes Pain Processing
    Researchers have identified several biological changes that contribute to central sensitization.
    One key factor involves glutamate, a neurotransmitter responsible for excitatory signaling in the brain. Elevated glutamate levels have been observed in brain regions associated with pain processing in individuals with fibromyalgia (Kathleen Sluka and Daniel Clauw, 2023).


    Glutamate increases neuronal activity. When glutamate levels rise, neurons become easier to activate and more responsive to incoming signals.
    At the same time, the nervous system loses some of its natural braking system.
    The brain normally relies on descending inhibitory pain pathways that help regulate pain signals before they reach conscious awareness. Evidence suggests that these pathways function less effectively in fibromyalgia (Winfried Häuser, Mary-Ann Fitzcharles, and Claudia Sommer, 2022).


    When excitatory signaling increases and inhibitory control decreases, the nervous system becomes primed to amplify pain.
    The Role of the Spinal Cord in Chronic Pain
    The spinal cord plays an important role in central sensitization.
    Sensory nerves transmit signals to neurons in the dorsal horn of the spinal cord, which then relay those signals to the brain.
    When central sensitization occurs, these spinal neurons become more responsive.
    Researchers often describe this process as wind-up.
    Wind-up occurs when repeated stimulation causes spinal neurons to respond more strongly each time they are activated.

    Over time, the system becomes increasingly reactive.
    This heightened sensitivity can allow pain to persist long after the original trigger has resolved.
    Brain Imaging Evidence in Fibromyalgia
    Brain imaging studies provide strong evidence that central sensitization occurs in fibromyalgia.
    Functional MRI research shows that individuals with fibromyalgia demonstrate greater activity in brain regions responsible for pain processing, even when exposed to sensory stimuli that healthy individuals would not perceive as painful (Kathleen Sluka and Daniel Clauw, 2023).
    These regions include:
    the insula
    the anterior cingulate cortex
    the somatosensory cortex


    Together, these structures form part of the brain’s pain processing network, sometimes referred to as the pain matrix.
    Researchers have also observed changes in how these regions communicate with each other. These changes may contribute to symptoms such as fatigue, sensory sensitivity, and cognitive difficulties.
    Why Fibromyalgia Pain Is Widespread
    Fibromyalgia pain rarely stays in one place. Instead, it often affects multiple regions of the body.
    Central sensitization helps explain why this happens.
    When the nervous system becomes hypersensitive, neurons begin responding to signals from multiple parts of the body rather than a single injury site. The entire system becomes more reactive.


    As a result, pain can migrate between body regions or occur simultaneously in several areas.
    This is why fibromyalgia is often described as a disorder of pain processing rather than tissue damage.

    Common Triggers That May Lead to Central Sensitization
    Researchers believe central sensitization can develop after different types of physiological stress.
    Common triggers reported by patients include:
    physical injury or trauma
    infections or viral illness
    autoimmune diseases
    chronic psychological stress
    disrupted sleep
    For many individuals with fibromyalgia, symptoms begin after a significant physiological event such as surgery, illness, or prolonged stress (Winfried Häuser, Mary-Ann Fitzcharles, and Claudia Sommer, 2022).
    Genetic susceptibility may also influence how easily central sensitization develops.


    Why Traditional Pain Medications Often Do Not Work
    Central sensitization also explains why many traditional pain treatments are ineffective for fibromyalgia.
    Medications such as nonsteroidal anti-inflammatory drugs primarily target inflammation in tissues. However, fibromyalgia is classified as a nociplastic pain condition, meaning the main issue lies in the nervous system’s processing of pain signals rather than tissue inflammation.
    For this reason, medications that affect neurotransmitters involved in pain signaling are sometimes more effective.
    Examples include:
    duloxetine
    milnacipran
    pregabalin
    These medications work by influencing neurotransmitters involved in pain modulation.
    Other Conditions Linked to Central Sensitization
    Central sensitization is not unique to fibromyalgia. Similar mechanisms have been identified in several other chronic pain disorders.


    These include:
    chronic migraine
    irritable bowel syndrome
    temporomandibular disorder
    chronic fatigue syndrome
    complex regional pain syndrome
    Because these conditions share similar neurological mechanisms, researchers sometimes refer to them collectively as central sensitivity syndromes (Jo Nijs, Lotte Lahousse, Efthymios Kapreli, Panagiota Bilika, İbrahim Saraçoğlu, Anneleen Malfliet, Iris Coppieters, and Mira Meeus, 2021).

    Why Understanding Central Sensitization Matters


    Central sensitization reflects real biological changes in the nervous system.
    For people living with fibromyalgia, understanding this concept can help explain why pain persists even when laboratory tests or imaging appear normal.
    Fibromyalgia is not simply stress or emotional distress. It involves measurable differences in how the nervous system processes sensory signals.
    As research continues to evolve, a deeper understanding of central sensitization may lead to more targeted therapies for chronic pain.

    References


    Häuser, Winfried, Fitzcharles, Mary-Ann, and Sommer, Claudia. (2022). Fibromyalgia syndrome: Underlying mechanisms and clinical implications. The Lancet Rheumatology, 4(9), e629–e637. https://doi.org/10.1016/S2665-9913(22)00159-8⁠.


    Nijs, Jo, Lahousse, Lotte, Kapreli, Efthymios, Bilika, Panagiota, Saraçoğlu, İbrahim, Malfliet, Anneleen, Coppieters, Iris, and Meeus, Mira. (2021). Nociplastic pain criteria or recognition of central sensitization? Pain Physician, 24(6), E891–E899.


    Paroli, Massimo, Gioia, Claudio, Accapezzato, Daniele, and Caccavale, Riccardo. (2024). Inflammation, autoimmunity, and infection in fibromyalgia: A narrative review. International Journal of Molecular Sciences, 25(11), 5922. https://doi.org/10.3390/ijms25115922⁠.


    Sluka, Kathleen, and Clauw, Daniel. (2023). Neurobiology of fibromyalgia and chronic widespread pain. Nature Reviews Rheumatology, 19(5), 293–304. https://doi.org/10.1038/s41584-023-00917-6⁠.