Neurophysiopathogenesis of fibromyalgia syndrome: a unified hypothesis

The science of fibromyalgia

Fibromyalgia (FM) is a common chronic widespread pain disorder. Our understanding of FM has increased substantially in recent years with extensive research suggesting a neurogenic origin for the most prominent symptom of FM, chronic widespread pain. Neurochemical imbalances in the central nervous system are associated with central amplification of pain perception characterized by allodynia (a heightened sensitivity to stimuli that are not normally painful) and hyperalgesia (an increased response to painful stimuli). Despite this increased awareness and understanding, FM remains undiagnosed in an estimated 75% of people with the disorder. Clinicians could more effectively diagnose and manage FM if they better understood its underlying mechanisms. Fibromyalgia is a disorder of pain processing. Evidence suggests that both the ascending and descending pain pathways operate abnormally, resulting in central amplification of pain signals, analogous to the "volume control setting" being turned up too high. Patients with FM also exhibit changes in the levels of neurotransmitters that cause augmented central nervous system pain processing; levels of several neurotransmitters that facilitate pain transmission are elevated in the cerebrospinal fluid and brain, and levels of several neurotransmitters known to inhibit pain transmission are decreased. Pharmacological agents that act centrally in ascending and/or descending pain processing pathways, such as medications with approved indications for FM, are effective in many patients with FM as well as other conditions involving central pain amplification. Research is ongoing to determine the role of analogous central nervous system factors in the other cardinal symptoms of FM, such as fatigue, nonrestorative sleep, and cognitive dysfunction.

A brain-derived neurotrophic factor polymorphism Val66Met identifies fibromyalgia syndrome subgroup with higher body mass index and C-reactive protein

A common single nucleotide polymorphism (SNP) in the gene of brain-derived neurotrophic factor (BDNF) results from a substitution at position 66 from valine (Val) to methionine (Met) and may predispose to human neuropsychiatric disorders. We proposed to determine whether these BDNF gene SNPs were associated with fibromyalgia syndrome (FMS) and/or any of its typical phenotypes. Patients with FMS (N = 95) and healthy normal controls (HNC, N = 58) were studied. Serum high-sensitivity C-reactive protein (hsCRP) levels were measured using an enzyme-linked immunosorbent assay (ELISA). The BDNF SNPs were determined using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP).The BDNF SNP distribution was 65 (68%) Val/Val, 28 (30%) Val/Met, and 2 (2%) Met/Met for FMS and 40 (69%), 17(29%), and 1 (2%) for HNC, respectively. The serum high-sensitivity C-reactive protein (hsCRP)and body mass index (BMI) in FMS were higher than in HNC. The FMS with BDNF Val66Val had significantly higher mean BMI (P = 0.0001) and hsCRP (P = 0.02) than did FMS carrying the Val66Met genotype. This pattern was not found in HNC. Phenotypic measures of subjective pain, pain threshold, depression, or insomnia did not relate to either of the BDNF SNPs in FMS. The relative distribution BDNF SNPs did not differ between FMS and HNC. The BDNF Val66Met polymorphism is not selective for FMS. The BDNF Val66Val SNP identifies a subgroup of FMS with elevated hsCRP and higher BMI. This is the first study to associate a BDNF polymorphism with a FMS subgroup phenotype.

Improving the recognition and diagnosis of fibromyalgia

Fibromyalgia (FM) is a chronic widespread pain disorder often seen in primary care practices. Advances in the understanding of FM pathophysiology and clinical presentation have improved the recognition and diagnosis of FM in clinical practice. Fibromyalgia is a clinical diagnosis based on signs and symptoms and is appropriate for primary care practitioners to make. The hallmark symptoms used to identify FM are chronic widespread pain, fatigue, and sleep disturbances. Awareness of common mimics of FM and comorbid disorders will increase confidence in establishing a diagnosis of FM.

Genetic polymorphisms of the beta2-adrenergic receptor relate to guanosine protein-coupled stimulator receptor dysfunction in fibromyalgia syndrome

OBJECTIVE

To determine the genotype frequencies of ß(2)-adrenergic receptor (ß(2)AR) gene polymorphisms (Gly16Arg, Glu27Gln) in patients with fibromyalgia syndrome (FM) by comparison with unrelated healthy controls. We sought any clinical association with these polymorphisms and determined whether the polymorphisms would associate with a biologic guanosine protein-coupled stimulator receptor (Gs) dysfunction in FM.

METHODS

Study subjects included 97 clinically characterized patients with FM and 59 controls. The ß(2)AR polymorphisms at codons 16 and 27 were determined using polymerase chain reaction-restriction fragment length polymorphism. The Gs functions of peripheral blood mononuclear cells (PBMC) were tested using isoproterenol (ISO) as the adrenergic Gs ligand and measuring intracellular cyclic adenosine monophosphate (cAMP) levels.

RESULTS

The frequency of the ß(2)AR gene polymorphism Gly16Arg in FM (43.5%) was significantly lower than in controls (63.2%), suggesting that this genotype might have some effect on the risk of developing FM. The only clinical association in FM was with sleep dysfunction. Patients with FM who carried the ß(2)AR polymorphism Arg16Arg also exhibited significantly lower PBMC basal cAMP levels (p < 0.05) and lower ISO-stimulated cAMP levels (p < 0.05) than FM carrying Gly16Gly or Gly16Arg.

CONCLUSION

This confirms a relationship between ß(2)AR polymorphism and FM. It is the first study to demonstrate ß(2)AR polymorphism-related differences in intracellular cAMP responses of FM PBMC after ß(2)AR stimulation in vitro. These findings may explain some of the differences in responsiveness of FM subgroups to the adrenergic agonist medications currently approved for FM treatment.

The FIBRO System: A Rapid Strategy for Assessment and Management of Fibromyalgia Syndrome

Fibromyalgia syndrome (FMS) is a complex disorder of widespread pain and tenderness associated with numerous other symptoms including fatigue, cognitive dysfunction, nonrestorative sleep, depression, anxiety, and stiffness. While new diagnostic criteria and previous management guidelines require quantitation of the severity of associated FMS symptoms experienced by individual patients, no system for rapid patient assessment has been made available to provide a basis for diagnosis, treatment selection and follow-up for clinicians in busy practices who have limited time. This review presents the FIBRO System, an easily remembered system for FMS symptom quantitation using the FIBRO mnemonic along with verbal questions on simple 0-10 scales to assess symptom severity (the FIBRO Problem Scale) and response to treatment (the FIBRO Change Scale) along with recommendations for pharmacologic and nonpharmacologic therapies to address individual FIBRO symptoms. This symptom-based approach can improve the care of FMS patients by providing a comprehensive, focused assessment in limited time.