Collagen crosslinks in fibromyalgia

Factors associated with keratoconus in Israel-A cross-sectional population-based study

PURPOSE

To identify potential factors associated with keratoconus.

METHODS

This cross-sectional study included data from Israel's largest healthcare provider for the years 2005-2020. Keratoconus patients and age-matched controls were identified. Demographic factors and comorbid conditions, including smoking, diabetes mellitus, asthma, myalgia, mental retardation, Down syndrome, atopic dermatitis and allergy/allergic rhinitis, were compared between the two cohorts. The independent risk factors associated with keratoconus were determined using a multivariable conditional logistic regression model.

RESULTS

Overall, 145 508 subjects were reviewed of which 13 228 were keratoconus patients. A ten-fold group (n = 132 280) of age-matched control subjects served as controls for comparisons. In multivariable analysis, several factors were found to be significantly associated with keratoconus. Male gender (OR = 1.27, p < 0.001), Arab ethnicity (OR = 1.50, p < 0.001), diabetes (OR = 1.19, p < 0.001), asthma (OR = 1.50, p < 0.001), myalgia (OR = 1.09, p = 0.02), mental retardation (OR = 2.63, p < 0.001), atopic dermatitis (OR = 1.35, p < 0.001) and allergic rhinitis (OR = 1.21, p < 0.001) were significantly associated with keratoconus. Smoking was significantly protective of keratoconus (OR = 0.66, p < 0.001).

CONCLUSIONS

This population-based study reports male gender, Arab ethnicity, diabetes, asthma, myalgia, mental retardation/Down syndrome, atopic dermatitis and allergic rhinitis as factors associated with keratoconus while smoking demonstrates a protective effect. The results of this study could guide enhanced screening strategies and early interventions, particularly for high-risk groups.

“Long COVID-19” and viral “fibromyalgia-ness”: Suggesting a mechanistic role for fascial myofibroblasts (Nineveh, the shadow is in the fascia)

The coronavirus pandemic has led to a wave of chronic disease cases; “Long COVID-19” is recognized as a new medical entity and resembles “fibromyalgia” which, likewise, lacks a clear mechanism. Observational studies indicate that up to 30%–40% of convalescent COVID-19 patients develop chronic widespread pain and fatigue and fulfill the 2016 diagnostic criteria for “fibromyalgia.” A recent study suggested a theoretical neuro-biomechanical model (coined “Fascial Armoring”) to help explain the pathogenesis and cellular pathway of fibromyalgia, pointing toward mechanical abnormalities in connective tissue and fascia, driven by contractile myo/fibroblasts and altered extracellular matrix remodeling with downstream corresponding neurophysiological aberrations. This may help explain several of fibromyalgia’s manifestations such as pain, distribution of pain, trigger points/tender spots, hyperalgesia, chronic fatigue, cardiovascular abnormalities, metabolic abnormalities, autonomic abnormalities, small fiber neuropathy, various psychosomatic symptoms, lack of obvious inflammation, and silent imaging investigations. Pro-inflammatory and pro-fibrotic pathways provide input into this mechanism via stimulation of proto/myofibroblasts. In this hypothesis and theory paper the theoretical model of Fascial Armoring is presented to help explain the pathogenesis and manifestations of “long COVID-19” as a disease of immuno-rheumo-psycho-neurology. The model is also used to make testable experimental predictions on investigations and predict risk and relieving factors.

Metabolomics analysis of plasma samples of patients with fibromyalgia and electromagnetic sensitivity using GC-MS technique

Fibromyalgia (FM) is a chronic and systemic condition that causes widespread chronic pain, asthenia, and muscle stiffness, as well as in some cases depression, anxiety, and disorders of the autonomic system. The exact causes that lead to the development of FM are still unknown today. In a percentage of individuals, the symptoms of FM are often triggered and/or exacerbated by proximity to electrical and electromagnetic devices. Plasma metabolomic profile of 54 patients with fibromyalgia and self-reported electromagnetic sensitivity (IEI-EMF) were compared to 23 healthy subjects using gas chromatography-mass spectrometry (GC-MS) coupled with multivariate statistical analysis techniques. Before the GC-MS analysis the plasma samples were extracted with a modified Folch method and then derivatized with methoxamine hydrochloride in pyridine solution and N-trimethylsilyltrifuoroacetamide. The combined analysis allowed to identify a metabolomic profile able of distinguishing IEI-EMF patients and healthy subjects. IEI-EMF patients were therefore characterized by the alteration of 19 metabolites involved in different metabolic pathways such as energy metabolism, muscle, and pathways related to oxidative stress defense and chronic pain. The results obtained in this study complete the metabolomic "picture" previously investigated on the same cohort of IEI-EMF patients with ¹H-NMR spectroscopy, placing a further piece for better understanding the pathophysiological mechanisms in patients with IEI-EMF.

Functions and Mechanisms of Pro-Lysyl Oxidase Processing in Cancers and Eye Pathologies with a Focus on Diabetic Retinopathy

Lysyl oxidases are multifunctional proteins derived from five lysyl oxidase paralogues (LOX) and lysyl oxidase-like 1 through lysyl oxidase-like 4 (LOXL1-LOXL4). All participate in the biosynthesis of and maturation of connective tissues by catalyzing the oxidative deamination of lysine residues in collagens and elastin, which ultimately results in the development of cross-links required to function. In addition, the five LOX genes have been linked to fibrosis and cancer when overexpressed, while tumor suppression by the propeptide derived from pro-LOX has been documented. Similarly, in diabetic retinopathy, LOX overexpression, activity, and elevated LOX propeptide have been documented. The proteolytic processing of pro-forms of the respective proteins is beginning to draw attention as the resultant peptides appear to exhibit their own biological activities. In this review we focus on the LOX paralogue, and what is known regarding its extracellular biosynthetic processing and the still incomplete knowledge regarding the activities and mechanisms of the released lysyl oxidase propeptide (LOX-PP). In addition, a summary of the roles of both LOX and LOX-PP in diabetic retinopathy, and brief mentions of the roles for LOX and closely related LOXL1 in glaucoma, and keratoconus, respectively, are included.

Fascial preadipocytes: another missing piece of the puzzle to understand fibromyalgia?

Fibromyalgia (FM) syndrome is a chronic condition causing pain, affecting approximately 0.5%-6% of the developed countries' population, and on average, 2% of the worldwide population. Despite the large amount of scientific literature available, the FM etiology is still uncertain. The diagnosis is based on the clinical presentation and the severity of the symptomatology. Several studies pointed out pathological alterations within the central nervous system, suggesting that FM could originate from a central sensitization of the pain processing centers. Research supports the thesis of a peripheral neuropathic component, with the finding of axonal damages. The fibromyalgia patient has many myofascial system abnormalities, such as pain and fatigue, impairing the symptomatic profile. This paper revises the myopathic compensations, highlighting the possible role of the fascia in generating symptoms, being aware of the new information about the fascia's activity in stimulating inflammation and fat cell production.

Bone mass and vitamin D levels in women with a diagnosis of fibromyalgia

No differences in either bone mineral density or serum 25OHD levels have been found between 205 women with fibromyalgia (both pre- and postmenopausal) and their controls. However, a lack of the expected 25OHD summer rise was observed in patients.

INTRODUCTION

Contradictory data have been published regarding a possible association between fibromyalgia and osteoporosis or hypovitaminosis D. Most studies, however, have been performed in small size samples and have excluded postmenopausal women. We decided to study this association in a larger sample of fibromyalgia patients including both pre- and postmenopausal women.

METHODS

Two hundred five patients were recruited from a clinic specializing in fibromyalgia and 205 healthy controls were enrolled from the census of a Primary Care Center. Controls were matched with patients by age and the time of the year they were included in the study. Bone mineral density (BMD) was measured by DXA. Serum 25OHD, iPTH, P1NP, and CTX were also determined.

RESULTS

BMD was similar in both groups (lumbar spine, 0.971 ± 0.146 g/cm(2) in patients and 0.970 ± 0.132 g/cm(2) in controls; femoral neck, 0.780 ± 0.122 g/cm(2) and 0.785 ± 0.117 g/cm(2), respectively). 25OHD levels were also similar: 23.0 ± 9.5 ng/ml and 24.1 ± 9.6 ng/ml. However, while controls showed the usual summer rise in 25OHD, fibromyalgia patients did not. PTH did not show seasonal changes, but on average was higher in patients (51 pg/ml vs. 48 pg/ml; p = 0.034). P1NP or CTX were similar in both groups.

CONCLUSIONS

No differences in BMD were found between patients and controls. As for 25OHD, a lack of its expected summer rise was observed. It is doubtful whether this has any homeostatic consequence. We consider that the association reported in other studies is merely circumstantial, and not due to the intrinsic characteristics of these disorders.

Serum prolidase enzyme activity and oxidative status in patients with fibromyalgia

OBJECTIVE

This study was performed to investigate serum prolidase enzyme activity and oxidative stress in patients diagnosed with fibromyalgia (FM).

METHODS

The study population consisted of 40 patients with a previous diagnosis of FM and 30 healthy subjects. We measured serum prolidase enzyme activity, total antioxidant status (TAS), total oxidative status (TOS), oxidative stress index (OSI), and paraoxonase-1 (PON-1) levels.

RESULTS

On average, FM patients were diagnosed within 3.2 years of symptom onset, and patients had a mean of 14 tender points. There were no significant differences between patients and controls in age, body mass index, serum TAS, or PON-1 levels. However, patients with FM demonstrated higher serum prolidase activity, TOS, and OSI than the control group. Serum prolidase activity was positively correlated with serum TOS, OSI, and visual analog scale pain and fatigue scores. No correlation was found between serum prolidase activity and FM duration or the average number of tender points.

DISCUSSION

Our results demonstrate a previously unreported association between serum prolidase enzyme activity and FM. Increased prolidase activity may contribute to the pathogenesis of FM, and measuring serum prolidase enzyme activity may be a useful FM biomarker.

Small fibre pathology in patients with fibromyalgia syndrome

Fibromyalgia syndrome is a clinically well-characterized chronic pain condition of high socio-economic impact. Although the pathophysiology is still unclear, there is increasing evidence for nervous system dysfunction in patients with fibromyalgia syndrome. In this case-control study we investigated function and morphology of small nerve fibres in 25 patients with fibromyalgia syndrome. Patients underwent comprehensive neurological and neurophysiological assessment. We examined small fibre function by quantitative sensory testing and pain-related evoked potentials, and quantified intraepidermal nerve fibre density and regenerating intraepidermal nerve fibres in skin punch biopsies of the lower leg and upper thigh. The results were compared with data from 10 patients with monopolar depression without pain and with healthy control subjects matched for age and gender. Neurological and standard neurophysiological examination was normal in all patients, excluding large fibre polyneuropathy. Patients with fibromyalgia syndrome had increased scores in neuropathic pain questionnaires compared with patients with depression and with control subjects (P < 0.001 each). Compared with control subjects, patients with fibromyalgia syndrome but not patients with depression had impaired small fibre function with increased cold and warm detection thresholds in quantitative sensory testing (P < 0.001). Investigation of pain-related evoked potentials revealed increased N1 latencies upon stimulation at the feet (P < 0.001) and reduced amplitudes of pain-related evoked potentials upon stimulation of face, hands and feet (P < 0.001) in patients with fibromyalgia syndrome compared to patients with depression and to control subjects, indicating abnormalities of small fibres or their central afferents. In skin biopsies total (P < 0.001) and regenerating intraepidermal nerve fibres (P < 0.01) at the lower leg and upper thigh were reduced in patients with fibromyalgia syndrome compared with control subjects. Accordingly, a reduction in dermal unmyelinated nerve fibre bundles was found in skin samples of patients with fibromyalgia syndrome compared with patients with depression and with healthy control subjects, whereas myelinated nerve fibres were spared. All three methods used support the concept of impaired small fibre function in patients with fibromyalgia syndrome, pointing towards a neuropathic nature of pain in fibromyalgia syndrome.

Abnormal overexpression of mastocytes in skin biopsies of fibromyalgia patients

Formalin-fixed, paraffin-embedded skin tissue sections were collected from a matched cohort of 63 fibromyalgia syndrome (FMS) patients and 49 volunteers from the general population with both alpha1-antitrypsin (AAT) normal and deficiency variants. These tissues were examined for the expression of the broad-spectrum inhibitor AAT, the serine proteinases elastase and tryptase, the proinflammatory cytokines MCP-1 and TNFα, the endothelium biomarker VEGF, and the inflammation/nociception-related receptor PAR(2). The most relevant finding of the study was a significantly increased number of mast cells (MCs) in the papillary dermis of all FMS patients (greater than or equal to five to 14 per microscopic high power field) compared to zero to one in controls (p < 0.001). MCs strongly stained with tryptase, AAT and PAR(2) antibodies, exhibited a spindle-like shape and were uniformly distributed around blood vessels and appendages. MCP-1 and VEGF expressed weak/moderate positivity in most samples, with a higher expression in controls than in FMS patients (p < 0.001 and 0.051, respectively). No differences in elastase and TNFα were found between both groups. Moreover, no histological differences were found between samples from AAT deficiency and normal AAT phenotypes. Our results indicate that FMS is a MC-associated condition. MCs are present in skin and mucosal surfaces throughout the human body, and are easily stimulated by a number of physical, psychological, and chemical triggers to degranulate, releasing several proinflammatory products which are able to generate nervous peripheral stimuli causing CNS hypersensitivity, local, and systemic symptoms. Our findings open new avenues of research on FMS mechanisms and will benefit the diagnosis of patients and the development of therapeutics.

Detection of elevatedNε‐carboxymethyllysine levels in muscular tissue and in serum of patients with fibromyalgia

OBJECTIVES

To compare levels of the advanced glycation end product (AGE) N(epsilon)-carboxymethyllysine (CML) present in the muscle tissue and in the serum of patients with fibromyalgia (FM) vs. healthy controls.

METHODS

The serum levels of CML were measured in 41 patients with FM and 81 healthy controls. The presence of CML, nuclear factor kappa B (NF-kappaB), the AGE receptor (RAGE), collagen types I, II, VI, and CD68-positive monocytes/macrophages in muscle tissue of 14 patients with FM was investigated by immunohistochemistry.

RESULTS

Patients with FM showed significantly increased serum levels of CML in comparison to healthy controls. The immunohistochemical investigation revealed a stronger staining for CML and NF-kappaB and more CD68-positive monocytes/macrophages in the muscle of FM patients. The collagens and CML were co-localized, suggesting that the AGE modifications were related to collagen. RAGE was absent in controls but a faint and patchy staining was seen in FM.

CONCLUSIONS

In the interstitial connective tissue of fibromyalgic muscles we found a more intensive staining of the AGE CML, activated NF-kappaB, and also higher CML levels in the serum of these patients compared to the controls. RAGE was only present in FM muscle. AGE modification of proteins causes reduced solubility and high resistance to proteolytic digestion of the altered proteins (e.g. AGE-modified collagens). AGEs can stimulate different types of cells by activation of the transcription factor NF-kappaB, mediated by specific receptors of AGEs (e.g. RAGE) on the cell surface. Both mechanisms may contribute to the development, perpetuation, and spreading of pain characteristic in FM patients.

Characteristic electron microscopic findings in the skin of patients with fibromyalgia—preliminary study

This blinded study was done to determine if there are any abnormal electron microscopic (EM) findings in the skin of fibromyalgia syndrome (FMS) patients, which might contribute to or be due to the increased pain sensitivity seen in this condition. Skin biopsy samples were obtained from 13 FMS patients and 5 control subjects. All tissues were prepared for EM examination by immediate prefixation in 2.5% glutaraldehyde for 2 h and postfixation in 1% osmium acid for 24 h. Ultrathin sections on grids were stained by uranyl acetate and lead citrate. Biopsies were read by an individual without knowledge of participant status. Five skin biopsies from healthy controls showed relatively even distribution of variegated sized unmyelinated axons sheathed well by complicatedly folded Schwann cell membranes. In tissues from 9/13 FMS patients, unmyelinated Schwann cells were noted to be ballooned, whereas this finding was not noted in any controls (p = 0.029). Axons in most patients trended towards being localized in the periphery of the unmyelinated Schwann cell sheaths (p = 0.002). Particularly, peripheral localization of axon in the unmyelinated Schwann cell sheath had a strong relationship with ballooning of Schwann cell (p = 0.042), simplified folding of Schwann cell sheath (p = 0.039) and smaller axon (p = 0.034). Myelinated nerve fibers were unremarkable. The EM findings seen in the skin of FMS patients show unusual patterns of unmyelinated nerve fibers as well as associated Schwann cells. If these findings are replicated in a larger study, these abnormalities may contribute to, or be due to, the lower pain threshold seen in FMS patients.

Skin biopsy findings: implications for the pathophysiology of fibromyalgia

The mechanisms responsible for symptom expression in fibromyalgia (FM) are complex. The most consistently detected objective abnormalities in FM involve pain-processing systems. Up to recently, central nervous system was a primary focus of investigations in FM. Although it is unlikely that FM occurs because of primary disorders of the peripheral tissues, there are still data to suggest that some abnormalities can be detected in the periphery. With the recognition of abnormalities in skin of some FM patients, it is now apparent that the role of peripheral nerve endings in FM is much greater than previously thought. The aim of this paper is to review literature concerning the skin biopsy findings of FM patients and discuss their potential relevance to FM. This paper suggests that patients with FM represent a state of the dysfunction of descending, antinociceptive pathways and low hypothalamic-pituitary-adrenal function. This state is further proposed to result in many skin biopsy findings associated with the disorder, including increased N-methyl-d-aspartate receptors subtype 2D expression, neurogenic inflammation and characteristic electron microscopic findings. Future direction of research would be identification of specific laboratory markers such as skin biopsy for diagnostic and clinical evaluation purposes in FM.

Is fibromyalgia a muscle disorder?

The presence of abnormalities in fibromyalgia muscle using current methodological approaches is well established. The more serious abnormalities are demonstrated by histologic studies particularly on electron microscopy: disorganisation of Z bands and abnormalities in the number and shape of mitochondria. Biochemical studies and P 31 magnetic resonance spectroscopy show inconstant abnormalities of ATP and phosphocreatine levels. Mitochondrial abnormalities reduced capillary circulation and thickened capillary endothelium may result in decreased availability of oxygen and impaired oxidative phosphorylation as well as ATP synthesis. These abnormalities do not seem to be the consequences of the much-discussed deconditioning of muscles although these consequences are not well known. Further studies of energy metabolism of the muscle during exercise are needed.

Urinary and plasma organic acids and amino acids in chronic fatigue syndrome

Previous work by others have suggested the occurrence of one or more chemical or metabolic 'markers' for ME/CFS including specific amino acids and organic acids and a number of unidentified compounds (CFSUM1, CFSUM2). We have shown elsewhere that CFSUM1 is partially derivatised pyroglutamic acid and CFSUM2 partially derivatised serine and have suggested and demonstrated that the analytical methods used were unsuitable to identify or to accurately quantify urinary metabolites. We have now made a detailed analysis of plasma and urinary amino acids and of urinary organic acids from patients with ME/CFS and from three control groups. Fasting blood plasma and timed urine samples were obtained from 31 patients with CFS, 31 age and sex-matched healthy controls, 15 patients with depression and 22 patients with rheumatoid arthritis. Plasma and urinary amino acids and urinary organic acids were determined using established and validated methods and data compared by statistical analysis. None of the previously reported abnormalities in urinary amino acids or of organic acids could be confirmed. Results however provide some evidence in patients with ME/CFS for underlying inflammatory disease and for reduced intramuscular collagen with a lowered threshold for muscle micro-injury. These factors in combination may provide a basis for the fatigue and muscle pain that are the major symptoms in these patients.

A metabolic basis for fibromyalgia and its related disorders: the possible role of resistance to thyroid hormone

It has long been recognized that the symptom complex of fibromyalgia can be seen with hypothyroidism. Hypothyroidism may been categorized, like diabetes, into type I (hormone deficient) and type II (hormone resistant). Most cases of fibromyalgia fall into the latter category. The syndrome is reversible with treatment, and is usually of late onset. It is likely more often acquired than due to mutated receptors. Now that there is evidence to support the hypothesis that fibromyalgia may be due to thyroid hormone resistance, four major questions appear addressable. First, can a simple biomarker be found to help diagnose it? Second, what other syndromes similar to Fibromyalgia may share a thyroid-resistant nature? Third, in non-genetic cases, how is resistance acquired? Fourth, what other methods of treatment become available through this new understanding? Preliminary evidence suggests that serum hyaluronic acid is a simple, inexpensive, sensitive, and specific test that identifies fibromyalgia. Overlapping symptom complexes suggest that chronic fatigue syndrome, Gulf war syndrome, premenstrual syndrome, post traumatic stress disorder, breast implant silicone sensitivity syndrome, bipolar affective disorder, systemic candidiasis, myofascial pain syndrome, and idiopathic environmental intolerance are similar enough to fibromyalgia to merit investigation for possible thyroid resistance. Acquired resistance may be due most often to a recently recognized chronic consumptive coagulopathy, which itself may be most often associated with chronic infections with mycoplasmids and related microbes or parasites. Other precipitants of thyroid resistance may use this or other paths as well. In addition to experimentally proven treatment with supraphysiologic doses of thyroid hormone, the thyroid-resistant disorders might be treatable with anti-hypercoagulant, anti-infective, insulin-sensitizing, and hyaluronolytic strategies.

Assessment and Recommendations on Factors Contributing to Preanalytical Variability of Urinary Pyridinoline and Deoxypyridinoline

Background: Pyridinoline (PYD) and deoxypyridinoline (DPD) are two of the most extensively characterized biochemical bone markers, but the interpretation of results is hampered by biologic and other preanalytical variability. We reviewed factors contributing to preanalytical variation of pyridinium cross-links in urine.

Methods: We searched four databases for English-language reports on PYD and/or DPD in urine. Searches were restricted to humans, except for studies of stability, when the search was expanded to other species. The 599 identified articles were supplemented with references from those articles and with articles known to the authors.

Results: The mean reported within-day variability was 71% for PYD (range, 57–78%) and 67% for DPD (range, 53–75%). The mean interday variability was 16% for both DPD and PYD (range for PYD, 12–21%; range for DPD, 5–24%). The mean intersubject variabilities across studies were 26% for PYD (range, 12–63%) and 34% for DPD (range, 8–98%) for healthy premenopausal women and 36% (range, 22–61%) and 40%, (range, 27–54%) for postmenopausal women, respectively. Specimen instability and errors in creatinine measurements were additional sources of variability.

Conclusions: Intra- and intersubject variability can be reduced by collecting specimens at a specific time of the day and by maintaining similar patient status at each specimen collection regarding factors such as medications and dietary supplements.

[What happens to the fibromyalgia syndrome?]

OBJECTIVE

To realize a clarification about fibromyalgia, attempting to consider diagnostic criteria, prevalence, pathophysiology and therapeutic approach.

METHOD

A systematic literature search was conducted to select articles about fibromyalgia and connected diseases. The database are Premedline, Medline and Medlineplus.

RESULTS

Fifty-eight articles about fibromyalgia and twelve articles about connected diseases were selected to realize this review of literature.

DISCUSSION

Fibromyalgia constitutes a syndrome characterized by widespread musculo-skeletal pain, present above the waist and below the waist and in the axial skeleton. Widespread pain must have been present for at least three months. "Spasmophilie", chronic fatigue syndrome and myofascial syndrome represent diseases connected with fibromyalgia: differential diagnosis must be established. Researches related to fibromyalgia suggest a reduction of muscular performances associated with histological and biochemical anomalies. Patients are characterized by shorter and nonrestorative sleep. Psychological, neuroendocrine and central alterations appear often associated with fibromyalgia. The reduction of pressure tolerance and pain thresholds may be linked to the alterations of neuroendocrine substances. Literature recommend a multidisciplinary therapeutic approach in management of fibromyalgia.

CONCLUSION

The pathophysiologic mechanisms in fibromyalgia appear multiple and interdependent. With the aim to optimizing treatment, investigations are necessary to determine biochemical repercussions of various therapeutic approaches.

Fibromyalgia, chronic fatigue syndrome, and myofascial pain syndrome

Fibromyalgia was almost completely absent from an urban affluent population compared with poor urban and rural communities. Seventeen percent of Gulf War veterans with soft tissue syndromes had fibromyalgia, a much higher rate than was seen in previous studies of rheumatic disease in the military population. A state of central hyperexcitability in the nociceptive system was reported in fibromyalgia. Altered functioning of the stress-response system has been further documented in fibromyalgia and chronic fatigue syndrome. Administration of growth hormone to patients with fibromyalgia who have low levels of insulin-like growth factor 1 resulted in improvement in their symptoms and tenderness. An association between chronic fatigue syndrome and initial infections was demonstrated. A correlation between particular immunologic abnormalities and measures of disease severity was documented in chronic fatigue syndrome. Concomitant fibromyalgia in other rheumatic diseases was a major contributor to poor quality of life. A favorable outcome of fibromyalgia in children was reported; the majority of patients improved over 2 to 3 years of follow-up. Treatment of patients with fibromyalgia continues to be of limited success.

Current concepts in the pathophysiology of abnormal pain perception in fibromyalgia

Fibromyalgia is a noninflammatory rheumatic disorder characterized by chronic widespread musculoskeletal pain. Although many studies have described the pain and other clinical symptoms associated with this disorder, the primary mechanisms underlying the etiology of fibromyalgia remain elusive. This article reviews recent data supporting the links among each of three systems--the musculoskeletal system, the neuroendocrine system, and the central nervous system (CNS), all of which appear to play major roles in fibromyalgia pathophysiology--and pain in fibromyalgia, and concludes by presenting a model of the pathophysiology of abnormal pain perception in fibromyalgia which integrates the research findings described.