T Cell Subpopulations in the Physiopathology of Fibromyalgia: Evidence and Perspectives

Fibromyalgia: A Review of the Pathophysiological Mechanisms and Multidisciplinary Treatment Strategies

Fibromyalgia is a syndrome characterized by chronic widespread musculoskeletal pain, which may or may not be associated with muscle or joint stiffness, accompanied by other symptoms such as fatigue, sleep disturbances, anxiety, and depression. It is a highly prevalent condition globally, being considered the third most common musculoskeletal disorder, following lower back pain and osteoarthritis. It is more prevalent in women than in men, and although it can occur at any age, it is more common between the ages of thirty and thirty-five. Although the pathophysiology and etiopathogenesis remain largely unknown, three underlying processes in fibromyalgia have been investigated. These include central sensitization, associated with an increase in the release of both excitatory and inhibitory neurotransmitters; peripheral sensitization, involving alterations in peripheral nociceptor signaling; and inflammatory and immune mechanisms that develop concurrently with the aforementioned processes. Furthermore, it has been determined that genetic, endocrine, psychological, and sleep disorders may influence the development of this pathology. The accurate diagnosis of fibromyalgia remains challenging as it lacks specific diagnostic biomarkers, which are still under investigation. Nonetheless, diagnostic approaches to the condition have evolved based on the use of scales and questionnaires for pain identification. The complexity associated with this pathology makes it difficult to establish a single effective treatment. Therefore, treatment is multidisciplinary, involving both pharmacological and non-pharmacological interventions aimed at alleviating symptoms. The non-pharmacological treatments outlined in this review are primarily related to physiotherapy interventions. The effectiveness of physical exercise, both on land and in water, as well as the application of electrotherapy combined with transcranial therapy and manual therapy has been highlighted. All of these interventions aim to improve the quality of life of patients highly affected by fibromyalgia.

Immune Dysregulation, Inflammation in Characterizing Women with Vulvodynia, Depression, and Both

Background: Depression and vulvodynia are often comorbid. The onset of depression and vulvodynia may be immune and/or stress/environmentally induced. We explored whether vulvodynia, depression, or both occur in response to a Th1-mediated versus Th2-mediated immune response. Materials and Methods: We analyzed data from a case-control study of clinically confirmed vulvodynia and history of depression determined through structured clinical interviews. Immune dysregulation and inflammation were categorized based on the following self-reported conditions: rheumatoid arthritis, Sjogren's disease, scleroderma, systemic lupus erythematosus, inflammatory bowel disease, fibromyalgia, osteoarthritis, polycystic ovarian syndrome, diabetes mellitus, uterine fibroids, asthma, atopic dermatitis, and allergic rhinitis. Logistic regression analyses were adjusted for marital status, body mass index, age, and pack years. Results: Women with systemic immune dysregulation had higher odds of depression (adjusted odds ratio [aOR] = 1.61, confidence interval [95% CI]: 0.65-3.98), vulvodynia (aOR = 2.45, 95% CI: 1.00-5.96), and comorbid depression and vulvodynia (aOR = 4.93, 95% CI: 2.19-11.10) versus neither condition. Women reporting local immune dysregulation had similar odds of depression (aOR = 1.89, 95% CI: 0.99-3.59), vulvodynia (aOR = 2.12, 95% CI: 1.08-4.18), and comorbid depression and vulvodynia (aOR = 1.96, 95% CI: 0.98-3.90). Women with Th2 inflammation had similar odds of depression (aOR = 2.23, 95% CI: 1.05-4.77) and vulvodynia (aOR = 2.56, 95% CI: 1.20-5.49). Women with Th1 or Th2 inflammation had similar odds of comorbid depression and vulvodynia (aOR = 3.03, 95% CI: 1.48-6.19; aOR = 3.14, 95% CI: 1.49-6.60, respectively). Conclusions: Our results suggest that an imbalance of cytokines, indicated by the presence of one or more immune-related health conditions, is associated with an increased risk of vulvodynia and/or depression.

Characteristics of pain and their relationship to disease activity in UK patients with Behçet's syndrome: a prospective cohort study

Background

Behçet's syndrome (BS) is a rare multi-systemic vasculitis of unknown aetiology. Fibromyalgia syndrome (FMS) is more prevalent in rheumatological conditions such-as BS, than the general population. However, there is limited research into the aetiology and characteristics of pain in BS.

Objectives

To describe the pain characteristics and incidence of FMS in people with BS and investigate their relationship with BS disease activity.

Methods

A cohort study of BS patients attending the Liverpool Behçet's Centre between February 2017 and March 2019. BS was defined using the International Study Group Criteria. BS severity was assessed using the Behçet's Disease Current Activity Form. FMS was determined from consultant diagnosis. Assessments of pain included: Pain Visual Analogue Scale (PVAS), Pain Mannequin, Brief Pain Inventory, EQ-5D-3L and Short Form McGill. Pain and FMS prevalence were compared between high and low disease activity.

Results

90% reported moderate-severe pain with a median PVAS score of 68/100 [38, 81]. 35.6% of participants had FMS and 46.5% experienced generalized pain. 76% of participants with high disease activity reported severe pain, compared to 39.1% with low disease activity (p = .003). Pain was more generalised in high disease activity (72%) compared to low disease activity (37.7%) (p = .003). FMS was more prevalent in the high disease activity group (52%) than the low disease activity group (29%) (p = .04).

Conclusions

This is the first study to explore pain in participants with BS in the United Kingdom. The majority of BS patients experience moderate-severe widespread pain. Severe widespread pain is more prevalent in those with high disease activity. We have demonstrated a relationship between high disease activity, worse pain intensity, and FMS. This paper contributes to the understanding of two conditions which remain to be fully understood, FMS and BS, and generates new hypotheses to describe the interplay between.

The frequency of psychiatric disorder co-morbidities in patients with fibromyalgia: A cross-sectional study in Iran

AIM

This study aimed to investigate psychiatric disorders in Iranian female patients with fibromyalgia (FM).

DESIGN

Female patients, newly diagnosed with FM, were interviewed by a psychiatrist for psychiatric assessments during a 2-year period.

METHODS

The diagnosis of the psychiatric disorders was based on the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5), and sleep quality was evaluated using the Pittsburgh Sleep Quality Index (PSQI).

RESULTS

In total, 159 patients with the mean age of 42.15 ± 9.89 were recruited in this study. Over 92% of the cases were also diagnosed with at least one type of psychiatric disorder. Sleep disorders (SDs, 90.57%), mood disorders (MDs, 52.83%), personality disorders (PDs, 40.25%) and anxiety disorders (ADs, 16.98%) were the most prevalent diagnoses among these patients. The logistic regression results correspondingly showed that suffering from Cluster-B PDs was associated with a higher prevalence rate of somatic symptom disorders (SSDs), with a p-value of 0.019 and an odds ratio (OR) of 2.7.

Regulatory T-cells and IL-5 mediate pain outcomes in a preclinical model of chronic muscle pain

Fibromyalgia (FM) is a chronic musculoskeletal pain disorder primarily diagnosed in women. Historically, clinical literature focusing on cytokines and immune cells has been inconsistent. However, recent key studies show several layers of immune system dysfunction in FM. Preclinically, studies of the immune system have focused on monocytes with little focus on other immune cells. Importantly, T-cells are implicated in the development and resolution of chronic pain states, particularly in females. Our previous work showed that monocytes from women with FM produced more interleukin 5 (IL-5) and systemic treatment of IL-5 reversed mechanical hypersensitivity in a preclinical model of FM. Typically, IL-5 is produced by T_H2-cells, so in this study we assessed T-cell populations and cytokine production in female mice using the acid-induced chronic muscle pain model of FM before and after treatment with IL-5. Two unilateral injections of pH4.0 saline, five days apart, into the gastrocnemius muscle induce long-lasting widespread pain. We found that peripheral (blood) regulatory T_helper-cells (CD4⁺ FOXP3+) are downregulated in pH4.0-injected mice, with no differences in tissue (lymph nodes) or CD8⁺ T-cell populations. We tested the analgesic properties of IL-5 using a battery of spontaneous and evoked pain measures. Interestingly, IL-5 treatment induced place preference in mice previously injected with pH4.0 saline. Mice treated with IL-5 show limited changes in T-cell populations compared to controls, with a rescue in regulatory T-cells which positively correlates with improved mechanical hypersensitivity. The experiments in this study provide novel evidence that downregulation of regulatory T-cells play a role in chronic muscle pain pathology in the acidic saline model of FM and that IL-5 signaling is a promising target for future development of therapeutics.

AKAP12 and RNF11 as Diagnostic Markers of Fibromyalgia and Their Correlation with Immune Infiltration

Fibromyalgia (FM) is a chronic nonarticular rheumatic disease mainly characterized by diffuse disseminated skeletal muscle pain, with varied symptoms including anxiety, sleep disturbance, and fatigue. Due to its unknown etiology and pathogenesis, FM is easily ignored in clinical practice, resulting in unclear diagnosis and difficult treatment. This study is aimed at investigating whether AKAP12 and RNF11 can be used as biomarkers for the diagnosis of FM and at determining their correlation with immune infiltration. The FM dataset in Gene Expression Omnibus (GEO) database was downloaded and was randomly divided into the training and test sets. Differentially expressed genes (DEGs) were screened, and functional correlation analysis was performed. Diagnostic markers of FM were screened and validated by random forest (RF). The least absolute shrinkage and selection operator (LASSO) logistic regression algorithm was then used to evaluate immune cell infiltration in the FM patients' peripheral blood. Finally, Spearman's rank correlation analysis was used to identify correlation between the diagnostic indexes and immune cell infiltration. A total of 69 DEGs were selected. Results indicated that AKAP12 and RNF11 can be used as diagnostic markers of FM, and CD8 + T cells might contribute in the pathogenesis of FM. In addition, AKAP12 was positively correlated with CD8 + T cells, while RNF11 was negatively correlated with CD8 + T cells. In conclusion, AKAP12 and RNF11 can be used as diagnostic indicators of FM, and CD8 + T cells may be involved in the occurrence and development of FM.

The Role of Neuro-Immune Interaction in Chronic Pain Conditions; Functional Somatic Syndrome, Neurogenic Inflammation, and Peripheral Neuropathy

Functional somatic syndromes are increasingly diagnosed in chronically ill patients presenting with an array of symptoms not attributed to physical ailments. Conditions such as chronic fatigue syndrome, fibromyalgia syndrome, or irritable bowel syndrome are common disorders that belong in this broad category. Such syndromes are characterised by the presence of one or multiple chronic symptoms including widespread musculoskeletal pain, fatigue, sleep disorders, and abdominal pain, amongst other issues. Symptoms are believed to relate to a complex interaction of biological and psychosocial factors, where a definite aetiology has not been established. Theories suggest causative pathways between the immune and nervous systems of affected individuals with several risk factors identified in patients presenting with one or more functional syndromes. Risk factors including stress and childhood trauma are now recognised as important contributors to chronic pain conditions. Emotional, physical, and sexual abuse during childhood is considered a severe stressor having a high prevalence in functional somatic syndrome suffers. Such trauma permanently alters the biological stress response of the suffers leading to neuroexcitatory and other nerve issues associated with chronic pain in adults. Traumatic and chronic stress results in epigenetic changes in stress response genes, which ultimately leads to dysregulation of the hypothalamic-pituitary axis, the autonomic nervous system, and the immune system manifesting in a broad array of symptoms. Importantly, these systems are known to be dysregulated in patients suffering from functional somatic syndrome. Functional somatic syndromes are also highly prevalent co-morbidities of psychiatric conditions, mood disorders, and anxiety. Consequently, this review aims to provide insight into the role of the nervous system and immune system in chronic pain disorders associated with the musculoskeletal system, and central and peripheral nervous systems.

Unbiased immune profiling reveals a natural killer cell-peripheral nerve axis in fibromyalgia

ABSTRACT

The pathophysiology of fibromyalgia syndrome (FMS) remains elusive, leading to a lack of objective diagnostic criteria and targeted treatment. We globally evaluated immune system changes in FMS by conducting multiparametric flow cytometry analyses of peripheral blood mononuclear cells and identified a natural killer (NK) cell decrease in patients with FMS. Circulating NK cells in FMS were exhausted yet activated, evidenced by lower surface expression of CD16, CD96, and CD226 and more CD107a and TIGIT. These NK cells were hyperresponsive, with increased CCL4 production and expression of CD107a when co-cultured with human leukocyte antigen null target cells. Genetic and transcriptomic pathway analyses identified significant enrichment of cell activation pathways in FMS driven by NK cells. Skin biopsies showed increased expression of NK activation ligand, unique long 16-binding protein, on subepidermal nerves of patients FMS and the presence of NK cells near peripheral nerves. Collectively, our results suggest that chronic activation and redistribution of circulating NK cells to the peripheral nerves contribute to the immunopathology associated with FMS.

Effect of ancient Khorasan wheat on gut microbiota, inflammation, and short-chain fatty acid production in patients with fibromyalgia

BACKGROUND

Fibromyalgia (FM) syndrome is mainly characterized by widespread pain, sleeping disorders, fatigue, and cognitive dysfunction. In many cases, gastrointestinal distress is also reported, suggesting the potential pathogenic role of the gut microbiota (GM). The GM is deeply influenced by several environmental factors, especially the diet, and recent findings highlighted significant symptom improvement in FM patients following various nutritional interventions such as vegetarian diet, low-fermentable oligosaccharides, disaccharides, monosaccharides, and polyols based diets, gluten-free diet, and especially an ancient grain supplementation. In particular, a recent study reported that a replacement diet with ancient Khorasan wheat led to an overall improvement in symptom severity of FM patients.

AIM

To examine the effects of ancient Khorasan wheat on the GM, inflammation, and short-chain fatty acid production in FM patients.

METHODS

After a 2-wk run-in period, 20 FM patients were enrolled in this randomized, double-blind crossover trial. In detail, they were assigned to consume either Khorasan or control wheat products for 8 wk and then, following an 8-wk washout period, crossed. Before and after treatments, GM characterization was performed by 16S rRNA sequencing while the fecal molecular inflammatory response and the short-chain fatty acids (SCFAs) were respectively determined with the Luminex MAGPIX detection system and a mass chromatography-mass spectrometry method.

RESULTS

The Khorasan wheat replacement diet, in comparison with the control wheat diet, had more positive effects on intestinal microbiota composition and on both the fecal immune and SCFAs profiles such as the significant increase of butyric acid levels (P = 0.054), candidatus Saccharibacteria (P = 9.95e-06) and Actinobacteria, and the reduction of Enterococcaceae (P = 4.97e-04). Moreover, the improvement of various FM symptoms along with the variation of some gut bacteria after the Khorasan wheat diet have been documented; in fact we reported positive correlations between Actinobacteria and both Tiredness Symptoms Scale (P < 0.001) and Functional Outcome of Sleep Questionnaire (P < 0.05) scores, between Verrucomicrobiae and both Widespread Pain Index (WPI) + Symptom Severity scale (SS) (P < 0.05) and WPI (P < 0.05) scores, between candidatus Saccharibacteria and SS score (P < 0.05), and between Bacteroidales and Sleep-Related and Safety Behaviour Questionnaire score (P < 0.05).

CONCLUSION

The replacement diet based on ancient Khorasan wheat results in beneficial GM compositional and functional modifications that positively correlate with an improvement of FM symptomatology.

Major Histocompatibility Complex Class II HLA-DRB1 Allelic Epitopes in Fibromyalgia

BACKGROUND

Preliminary evidence has pointed an association of the gene HLA-DRB1 with fibromyalgia. HLA-DRB1 alleles carrying the shared or susceptibility epitope encoding the five-amino acid motif QKRAA, QRRAA or RRRAA in positions 70 to 74 of the major histocompatibility complex class II DRβ chain are associated with several autoimmune diseases.

OBJECTIVE

The objective of this study was to test the hypothesis that susceptibility epitope-encoding HLA-DRB1 alleles are associated with fibromyalgia.

METHODS

Using a case-control design, the prevalence of susceptibility epitope-encoding HLADRB1 alleles in 27 white Caucasian patients fulfilling the revised diagnostic criteria for fibromyalgia of the American College of Rheumatology was compared with that in 27 white Caucasian ageand sex-matched healthy controls.

RESULTS

13 (48%) of the fibromyalgia patients had susceptibility epitope-coding HLA-DRB1 alleles compared with 15 (56%) of the controls (P = 0.785). The DRB1*01 allele encoding the protective epitope 70-DERAA-74 motif was found in one of the control subjects; none of the fibromyalgia patients had such a protective epitope.

CONCLUSION

While the present study does not provide evidence supporting the potential role of HLA-DRB1 in the etiology of fibromyalgia, it does not exclude the possibility that there is a polygenic component to a putative genetic causative role.

Post-COVID-19 syndrome: persistent neuroimaging changes and symptoms 9 months after initial infection

A previously healthy and active middle-aged woman acquired COVID-19 as an occupational exposure with subsequent persistent post-COVID-19 symptoms including headache, dyspnoea on exertion, chest pressure, tachycardia, anosmia, parosmia, persistent myalgia, vertigo, cognitive decline and fatigue. She presented to a tertiary medical centre for further evaluation after 9 months of persistent symptoms and had a largely unremarkable workup with the exception of a persistently elevated monocyte chemoattractant protein 1, blunted cardiovagal response and non-specific scattered areas of low-level hypometabolism at the bilateral frontal, left precuneus, occipital and parietal regions on PET scan.

The Female-Predominant Persistent Immune Dysregulation of the Post-COVID Syndrome

OBJECTIVE

To describe the clinical data from the first 108 patients seen in the Mayo Clinic post-COVID-19 care clinic (PCOCC).

METHODS

After Institutional Review Board approval, we reviewed the charts of the first 108 patients seen between January 19, 2021, and April 29, 2021, in the PCOCC and abstracted from the electronic medical record into a standardized database to facilitate analysis. Patients were grouped into phenotypes by expert review.

RESULTS

Most of the patients seen in our clinic were female (75%; 81/108), and the median age at presentation was 46 years (interquartile range, 37 to 55 years). All had post-acute sequelae of SARS-CoV-2 infection, with 6 clinical phenotypes being identified: fatigue predominant (n=69), dyspnea predominant (n=23), myalgia predominant (n=6), orthostasis predominant (n=6), chest pain predominant (n=3), and headache predominant (n=1). The fatigue-predominant phenotype was more common in women, and the dyspnea-predominant phenotype was more common in men. Interleukin 6 (IL-6) was elevated in 61% of patients (69% of women; P=.0046), which was more common than elevation in C-reactive protein and erythrocyte sedimentation rate, identified in 17% and 20% of cases, respectively.

CONCLUSION

In our PCOCC, we observed several distinct clinical phenotypes. Fatigue predominance was the most common presentation and was associated with elevated IL-6 levels and female sex. Dyspnea predominance was more common in men and was not associated with elevated IL-6 levels. IL-6 levels were more likely than erythrocyte sedimentation rate and C-reactive protein to be elevated in patients with post-acute sequelae of SARS-CoV-2 infection.

Denying the Truth Does Not Change the Facts: A Systematic Analysis of Pseudoscientific Denial of Complex Regional Pain Syndrome

Purpose

Several articles have claimed that complex regional pain syndrome (CRPS) does not exist. Although a minority view, it is important to understand the arguments presented in these articles. We conducted a systematic literature search to evaluate the methodological quality of articles that claim CRPS does not exist. We then examined and refuted the arguments supporting this claim using up-to-date scientific literature on CRPS.

Methods

A systematic search was conducted in MEDLINE, EMBASE and Cochrane CENTRAL databases. Inclusion criteria for articles were (a) a claim made that CRPS does not exist or that CRPS is not a distinct diagnostic entity and (b) support of these claims with subsequent argument(s). The methodological quality of articles was assessed if possible.

Results

Nine articles were included for analysis: 4 narrative reviews, 2 personal views, 1 letter, 1 editorial and 1 case report. Seven points of controversy were used in these articles to argue that CRPS does not exist: 1) disagreement with the label “CRPS”; 2) the “unclear” pathophysiology; 3) the validity of the diagnostic criteria; 4) CRPS as a normal consequence of immobilization; 5) the role of psychological factors; 6) other identifiable causes for CRPS symptoms; and 7) the methodological quality of CRPS research.

Conclusion

The level of evidence for the claim that CRPS does not exist is very weak. Published accounts concluding that CRPS does not exist, in the absence of primary evidence to underpin them, can harm patients by encouraging dismissal of patients’ signs and symptoms.

A Systematic Review of Fibromyalgia and Recent Advancements in Treatment: Is Medicinal Cannabis a New Hope?

Fibromyalgia syndrome (FMS) is a pain disorder characterized by chronic widespread pain, fatigue, and sleep disturbance, in the absence of any well-defined underlying organic disease. The exact pathophysiology and the mechanism which links different factors related to the disease is still unknown. Due to unknown precise pathogenesis, the coexistence of other diseases, and overlapping clinical features, FMS diagnosis may be laborious. Various treatment strategies are used, only a few Food and Drug Administration (FDA) approved, still we are facing challenges regarding effective treatment. Recently, medicinal cannabis has proven to be effective in chronic pain conditions such as osteoarthritis, neuropathic pain, and other non-cancer chronic pain. However, further research is needed about how the cannabinoid system works with the pain pathway. Using the fact that medicinal cannabis is effective in the treatment of chronic pain and certain rheumatic diseases, in this review, we aim to analyze the role of the cannabinoid system in fibromyalgia syndrome.

We followed Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) guidelines in searching PubMed, MEDLINE (through PubMed), PubMed Central, and Google Scholar using keywords "fibromyalgia, chronic pain, cannabis, cannabinoids, pharmacotherapy, alternative therapy" and Medical Subject Heading (MeSH) words.

After applying inclusion/exclusion criteria and checking for the quality assessment, 22 articles were retrieved and used for the analysis of the role of cannabis in the treatment of fibromyalgia. The two main compounds of cannabis with analgesic and anti-inflammatory properties are cannabidiol (CBD) and delta-9-tetrahydrocannabinol (THC), and their ratio determines the effect on various symptoms of FMS. We included studies regarding the use of cannabinoids in the treatment of fibromyalgia, investigating the use of nabilone, dronabinol (a synthetic analog of THC), Bedrocan (22.4 mg THC, <1 mg CBD), Bediol (13.4 mg THC, 17.8 mg CBD), and Bedrolite (18.4 mg CBD, <1 mg THC).

In the era of the coronavirus disease 2019 (COVID-19) pandemic and opioid crisis, many adverse outcomes are observed in the patients suffering from FMS due to lack of any definitive treatment and promising outcomes from the known treatment options, which led to the need for effective and safer treatment alternatives.

Although the studies reviewed in this article suggest that medical cannabis is a safe and effective treatment for fibromyalgia pain, several limitations regarding dosage, length of treatment, adverse effects, long-term follow-up, and dependence needs further investigation.

Is Fibromyalgia Associated with Borrelia Specific T Lymphocytes?

BACKGROUND

Although fibromyalgia is a common cause of chronic musculoskeletal pain, its aetiology and pathophysiology are uncertain. It has recently been suggested that fibromyalgia symptomatology represents a T lymphocyte-mediated immune response to pathogens which are known risk factors for autoimmune diseases. One major suggested candidate pathogen is the bacterial genus Borrelia. However, to date this hypothesis has not been tested.

OBJECTIVE

The aim was to carry out the first test of this hypothesis by comparing Borrelia-specific T lymphocyte reactivity in fibromyalgia patients and matched controls.

METHODS

The enzyme-linked immunospot was used to detect T-lymphocyte reactivity to Borrelia burgdorferi sensu stricto (full antigen); outer surface protein (Osp) A from Borrelia burgdorferi sensu stricto, Borrelia afzelii and Borrelia garinii; native OspC plus decorin binding protein A recombinant; and lymphocyte function antigen-1 (shared epitope) in 27 patients who fulfilled the revised diagnostic criteria for fibromyalgia of the American College of Rheumatology and in 26 control subjects. The assays were carried out blind to group status.

RESULTS

The two groups did not differ by age, sex or ethnicity. They did not differ significantly in respect of T lymphocyte reactivity to Borrelia burgdorferi sensu stricto (full antigen) (p = 0.847), Osp mix (p = 0.709) or lymphocyte function antigen-1 (p = 0.367).

CONCLUSION

This novel controlled study provides no evidence of an association between fibromyalgia and Borrelia-specific T lymphocytes.

Central Sensitization Phenotypes in Post Acute Sequelae of SARS-CoV-2 Infection (PASC): Defining the Post COVID Syndrome

OBJECTIVE

To develop and implement criteria for description of post COVID syndrome based on analysis of patients presenting for evaluation at Mayo Clinic Rochester between November 2019 and August 2020.

METHODS

A total of 465 patients with a history of testing positive for COVID-19 were identified and their medical records reviewed. After a thorough review, utilizing the DELPHI methods by an expert panel, 42 (9%) cases were identified with persistent central sensitization (CS) symptoms persisting after the resolution of acute COVID-19, herein referred to as Post COVID syndrome (PoCoS). In this report we describe the baseline characteristics of these PoCoS patients.

RESULTS

Among these 42 PoCoS patients, the mean age was 46.2 years (median age was 46.5 years). Pain (90%), fatigue (74%), dyspnea (43%), and orthostatic intolerance (38%) were the most common symptoms. The characteristics of an initial 14 patients were utilized for the development of clinical criteria via a modified Delphi Method by a panel of experts in central sensitization disorders. These criteria were subsequently applied in the identification of 28 additional cases of suspected PoCoS. A 2-reviewer system was used to analyze agreement with using the criteria, with all 28 cases determined to be either probable or possible cases by the reviewers. Inter-reviewer agreement using these proposed defining criteria was high with a Cohen's alpha of .88.

CONCLUSIONS

Here we present what we believe to be the first definitional criteria for Post COVID syndrome. These may be useful in clinical phenotyping of these patients for targeted treatment and future research.

Allodynia by Splenocytes From Mice With Acid-Induced Fibromyalgia-Like Generalized Pain and Its Sexual Dimorphic Regulation by Brain Microglia

Fibromyalgia (FM), a disease of unknown etiology characterized by chronic generalized pain, is partly recapitulated in an animal model induced by repeated acid saline injections into the gastrocnemius muscle. Here, we attempted to investigate the sex difference in pain hypersensitivity (mechanical allodynia and hypersensitivity to electrical stimulation) in the repeated acid saline-induced FM-like generalized pain (AcGP) model. The first unilateral acid injection into gastrocnemius muscle at day 0/D0 and second injection at D5 (post day 0, P0) induced transient and long-lasting mechanical allodynia, respectively, on both sides of male and female mice. The pretreatment with gonadectomy did not affect the first injection-induced allodynia in both sexes, but gradually reversed the second injection-induced allodynia in male but not female mice. Moreover, the AcGP in male mice was abolished by intracerebroventricular minocycline treatments during D4–P4 or P5–P11, but not by early treatments during D0–D5 in male but not female mice, suggesting that brain microglia are required for AcGP in late-onset and sex-dependent manners. We also found that the intravenous treatments of splenocytes derived from male but not female mice treated with AcGP caused allodynia in naive mice. In addition, the purified CD4⁺ T cells derived from splenocytes of acid-treated male mice retained the ability to cause allodynia in naive mice. These findings suggest that FM-like AcGP has multiple sexual dimorphic mechanisms.

Increased Pain Symptomatology Among Females vs. Males With Fragile X-Associated Tremor/Ataxia Syndrome

Individuals with the fragile X premutation report symptoms of chronic pain from multiple systems, have increased incidence of comorbid conditions where pain is a prominent feature, and pathophysiology that supports disrupted pain regulation, inflammation, and energy imbalance. Less is known about how pain manifests for the subpopulation of carriers that develop the motor and cognitive changes of fragile X-associated tremor and ataxia syndrome (FXTAS), and how pain may differ between men and women. We gathered data collected from 104 males and females with FXTAS related to chronic pain, comorbid conditions related to pain, and medications used for pain control to further explore the types of pain experienced and to better characterize how individuals with the fragile X premutation experience pain sensation across genders. We found that women experience significantly more pain symptoms than men, particularly allodynia (20 vs. 2.0%, p = 0.008), peripheral neuropathy pain (43.9 vs. 25.4%, p = 0.0488), migraine (43.9 vs. 14.5%, p = 0.0008), fibromyalgia (26.8 vs. 0%, p = 0.0071) and back pain (48.5 vs. 23.4%, p = 0.008). We found onset of peripheral neuropathy predicts the onset of ataxia (β = 0.63 ± 0.25, p = 0.019) and tremor (β = 0.56 ± 0.17, p = 0.004) across gender. Women also report significantly more anxiety (82.9 vs. 39.7%, p < 0.001), which has implications for ideal pain treatment. These pain symptoms need to be recognized in the medical history and treated appropriately, with consideration for overlapping comorbidities.

Pathogenic mechanisms of lipid mediator lysophosphatidic acid in chronic pain

A number of membrane lipid-derived mediators play pivotal roles in the initiation, maintenance, and regulation of various types of acute and chronic pain. Acute pain, comprising nociceptive and inflammatory pain warns us about the presence of damage or harmful stimuli. However, it can be efficiently reversed by opioid analgesics and anti-inflammatory drugs. Prostaglandin E₂ and I₂, the representative lipid mediators, are well-known causes of acute pain. However, some lipid mediators such as lipoxins, resolvins or endocannabinoids suppress acute pain. Various types of peripheral and central neuropathic pain (NeuP) as well as fibromyalgia (FM) are representatives of chronic pain and refractory owing to abnormal pain processing distinct from acute pain. Accumulating evidence demonstrated that lipid mediators represented by lysophosphatidic acid (LPA) are involved in the initiation and maintenance of both NeuP and FM in experimental animal models. The LPAR₁-mediated peripheral mechanisms including dorsal root demyelination, Ca_vα2δ1 expression in dorsal root ganglion, and LPAR₃-mediated amplification of central LPA production via glial cells are involved in the series of molecular mechanisms underlying NeuP. This review also discusses the involvement of lipid mediators in emerging research directives, including itch-sensing, sexual dimorphism, and the peripheral immune system.

Acupuncture decreased the risk of stroke among patients with fibromyalgia in Taiwan: A nationwide matched cohort study

BACKGROUND

The aim of this study was to investigate the effectiveness of acupuncture in decreasing the risk of stroke in patients with fibromyalgia.

METHODS

We enrolled patients who was newly diagnosed as having fibromyalgia between 1 January, 2000 and 31 December, 2010 from the Taiwanese National Health Insurance Research Database. The claim data for both the acupuncture cohort and non-acupuncture cohort were assessed from the index date to 31 December, 2013. A Cox regression model adjusted for age, sex, comorbidities, and drugs use was used to compare the hazard ratios of the two cohorts. The cumulative incidence of stroke was estimated by using the Kaplan-Meier method.

RESULTS

After performing a propensity score matching with a 1:1 ratio, there were 65,487 patients in the acupuncture and non-acupuncture cohorts with similar distributions in the baseline characteristics. The cumulative incidence of stroke was significantly lower in the acupuncture cohort (log-rank test, p < 0.001). In the follow-up period, 4,216 patients in the acupuncture cohort (11.01 per 1000 person-years) and 6,849 patients in the non-acupuncture cohort (19.82 per 1000 person-years) suffered from stroke (adjusted HR 0.53, 95% CI 0.51-0.55). Acupuncture favorably affected the incidence of stroke regardless of the patient's age, sex, comorbidities, and conventional drug use.

CONCLUSIONS

Our study found that acupuncture might have a beneficial effect on reducing the risk of stroke in patients with fibromyalgia in Taiwan. Additional clinical and basic science studies are warranted.

Excessive exercise induces cardiac arrhythmia in a young fibromyalgia mouse model

Background

Fibromyalgia patients experience cardiovascular complications in addition to musculoskeletal pain. This study aimed to investigate the cardiac effects of a prolonged shallow water gait in a fibromyalgia-induced young mouse model.

Methods

To produce a fibromyalgia mouse model, wild-type mice were administered an intraperitoneal injection of reserpine once a day for three days, and two primary experiments were performed. First, three types of gait tests were performed before and after the reserpine injections as follows: (i) 5 minutes of free gait outside the water, (ii) 1 minute of free gait in shallow warm water, and (iii) 5 minutes of free gait in shallow warm water. Second, electrocardiogram recordings were taken before and after the three gait tests. The average heart rate and heart rate irregularity scores were analyzed.

Results

Exercise-induced cardiac arrhythmia was observed at 1-minute gait in shallow water during the acute stage of induced FM in young mice. Further, both cardiac arrhythmia and a decrease in HR have occurred at 5-minute gait in shallow water at the same mice. However, this phenomenon was not observed in the wild-type mice under any test conditions.

Conclusion

Although a short-term free gait in shallow warm water may be advantageous for increasing the motor activity of FM-model mice, we should be aware of the risk of prolonged and excessive exercise-induced cardiac arrhythmia. For gait exercises in shallow water as a treatment in FM patients. We suggest a gradual increase in exercise duration may be warranted.

The Influence of Pro-inflammatory Cytokines and Genetic Variants in the Development of Fibromyalgia: A Traditional Review

Fibromyalgia is a complex syndrome characterized by widespread chronic pain, without any obvious etiology, and it is often accompanied by a constellation of symptoms such as fatigue, sleep disturbances and cognitive dysfunction, to name a few. The syndrome may be associated with a variety of autoimmune and psychiatric conditions. Fibromyalgia can occur with other musculoskeletal pathologies and its symptoms can overlap with other chronic painful conditions such as chronic myofascial pain syndromes seen in cervical and lumbar spinal osteoarthritis and degenerative disc disease. Gene polymorphisms have been related to a decreased pain threshold and an increased susceptibility to disorders associated with chronic pain. Some of those genetic variants might trigger the onset of fibromyalgia. Researchers are looking into the possible factors that might contribute to its pathophysiology. It is important to study the connections between pro-inflammatory cytokines and genetic variants in pain-related genes and their roles in predisposition and development of fibromyalgia. The objective of this review article is to provide a brief overview of the pro-inflammatory cytokines commonly associated with fibromyalgia, as well as to look into the genes that have shown some level of involvement in the development of fibromyalgia and its symptomatology.

Mirtazapine, an α2 Antagonist-Type Antidepressant, Reverses Pain and Lack of Morphine Analgesia in Fibromyalgia-Like Mouse Models

Treatment of fibromyalgia is an unmet medical need; however, its pathogenesis is still poorly understood. In a series of studies, we have demonstrated that some pharmacological treatments reverse generalized chronic pain but do not affect the lack of morphine analgesia in the intermittent cold stress (ICS)-induced fibromyalgia-like pain model in mice. Here we report that repeated intraperitoneal treatments with mirtazapine, which is presumed to disinhibit 5-hydroxytriptamine (5-HT) release and activate 5-HT1 receptor through mechanisms of blocking presynaptic adrenergic α2 and postsynaptic 5-HT2 and 5-HT3 receptors, completely reversed the chronic pain for more than 4 to 5 days after the cessation of treatments. The repeated mirtazapine treatments also recovered the morphine analgesia after the return of nociceptive threshold to the normal level. The microinjection of small interfering RNA (siRNA) adrenergic α2a receptor (ADRA2A) into the habenula, which showed a selective upregulation of α2 receptor gene expression after ICS, reversed the hyperalgesia but did not recover the morphine analgesia. However, both reversal of hyperalgesia and recovery of morphine analgesia were observed when siRNA ADRA2A was administered intracerebroventricularly. As the habenular is reported to be involved in the emotion/reward-related pain and hypoalgesia, these results suggest that mirtazapine could attenuate pain and/or augment hypoalgesia by blocking the habenular α2 receptor after ICS. The recovery of morphine analgesia in the ICS model, on the other hand, seems to be mediated through a blockade of α2 receptor in unidentified brain regions. SIGNIFICANCE STATEMENT: This study reports possible mechanisms underlying the complete reversal of hyperalgesia and recovery of morphine analgesia by mirtazapine, a unique antidepressant with adrenergic α2 and serotonergic receptor antagonist properties, in a type of intermittently repeated stress (ICS)-induced fibromyalgia-like pain model. Habenula, a brain region which is related to the control of emotional pain, was found to play key roles in the antihyperalgesia, whereas other brain regions appeared to be involved in the recovery of morphine analgesia in the ICS model.

Gene Expression Profiling in Fibromyalgia Indicates an Autoimmune Origin of the Disease and Opens New Avenues for Targeted Therapy

Fibromyalgia is a chronic disorder characterized by widespread pain and by several non-pain symptoms. Autoimmunity, small fiber neuropathy and neuroinflammation have been suggested to be involved in the pathogenesis of the disease. We have investigated the gene expression profile in peripheral blood mononuclear cells obtained from ten patients and ten healthy subjects. Of the 545,500 transcripts analyzed, 1673 resulted modulated in fibromyalgic patients. The majority of these genes are involved in biological processes and pathways linked to the clinical manifestations of the disease. Moreover, genes involved in immunological pathways connected to interleukin-17 and to Type I interferon signatures were also modulated, suggesting that autoimmunity plays a role in the disease. We then aimed at identifying differentially expressed Long non-coding RNAs (LncRNAs) functionally connected to modulated genes both directly and via microRNA targeting. Only two LncRNAs of the 298 found modulated in patients, were able to target the most highly connected genes in the fibromyalgia interactome, suggesting their involvement in crucial gene regulation. Our gene expression data were confirmed by real time PCR, by autoantibody testing, detection of soluble mediators and Th-17 polarization in a validation cohort of 50 patients. Our results indicate that genetic and epigenetic mechanisms as well as autoimmunity play a pivotal role in the pathogenesis of fibromyalgia.