Fibromualgia
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"fibromyalgia"[MeSH Terms] AND treatment
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Fibromyalgia
Definition
Fibromyalgia is the term for chronic widespread musculoskeletal pain for which no alternative structural or inflammatory cause can be identified. It belongs to a broader category now called nociplastic pain (or centralized pain / chronic overlapping pain conditions) - a third mechanism of pain distinct from nociceptive and neuropathic pain, driven primarily by central nervous system (CNS) dysfunction rather than peripheral tissue damage.
The same patient population may be labeled differently depending on the specialist they see:
- Gastroenterologist: IBS, functional dyspepsia, noncardiac chest pain
- Neurologist: chronic headache, unexplained facial pain
- Urologist: interstitial cystitis, chronic prostatitis, vulvodynia
- Dentist: temporomandibular disorder
Epidemiology
- Prevalence: 2-20% of the general population (varies by diagnostic criteria used)
- Chronic widespread pain affects 4-12% of the population at any time
- Women are affected ~1.5x more than men, consistent across ethnicities and cultures
- Comorbidity: present in 15-25% of patients with inflammatory rheumatic diseases (e.g., axial spondyloarthropathy, RA)
- Onset is typically triggered by environmental stressors (physical trauma, infections, psychological stress)
Pathophysiology
Central Sensitization (the core mechanism)
The pathophysiologic hallmark is augmented central pain processing. Patients are more tender everywhere in the body, not just at classical "tender points." Key mechanisms include:
- Decreased activity of descending analgesic pathways (spino-cortical inhibitory circuits)
- Diffuse increase in processing of all sensory stimuli - not just pain (explains hyperacusis, photophobia, sensitivity to smell)
- Functional MRI evidence: Application of mild pressure that healthy controls experience as touch is experienced as pain in fibromyalgia patients. The insula is consistently more active.
- Increased levels of substance P in cerebrospinal fluid (3-4x normal)
- Decreased levels of serotonin and norepinephrine (key inhibitory neurotransmitters in descending pain pathways)
Peripheral Contributions (emerging evidence)
- Autoantibodies binding to Fc receptors on peripheral sensory neurons
- Autoantibodies directed to satellite cells in dorsal root ganglia (DRG) that increase peripheral nociceptor sensitivity
- Widespread small fiber neuropathy in subgroups
These peripheral findings have not yet led to effective new interventions, and fibromyalgia is best understood as having both central and peripheral contributions.
Genetics
- Strong genetic component: linkage to chromosome 17p11.2-q11.2
- Candidate gene associations: GABRB3, TAAR1, GBP1
- Epigenetic mechanisms are also implicated, given the prominent role of environmental stressors
Clinical Features
| Domain | Symptoms |
|---|---|
| Pain | Widespread musculoskeletal pain; activity-related; often worsens with flares |
| Sleep | Non-restorative sleep; alpha-wave intrusion on polysomnography |
| Fatigue | Diurnal fatigue; often severe |
| Cognitive | "Fibro fog" - memory and concentration difficulties |
| Mood | Depression, anxiety |
| Comorbid pain | IBS, headache (especially tension/migraine), pelvic pain, TMD |
| Sensory | Allodynia, hyperalgesia, paresthesias, stiffness, feelings of tissue swelling; hyperacusis |
Diagnosis
2010/2016 ACR Diagnostic Criteria (no longer requires tender point count)
Diagnosis is based on:
- Widespread Pain Index (WPI) - count of body regions painful in the past week (0-19)
- Symptom Severity Scale (SSS) - scores fatigue, unrefreshing sleep, cognitive symptoms, and somatic symptoms (0-12)
Diagnosis requires: (WPI ≥ 7 AND SSS ≥ 5) OR (WPI 3-6 AND SSS ≥ 9)
Key point: Fibromyalgia can coexist with other diseases. Its presence does NOT exclude other diagnoses.
Mechanistic Classification of Pain Types
| Nociceptive | Neuropathic | Centralized/Nociplastic | |
|---|---|---|---|
| Cause | Inflammation/damage | Nerve damage/entrapment | CNS/systemic problem |
| Features | Well-localized pain | Dermatomal, lancinating, numbness | Widespread + fatigue + sleep + cognitive + mood |
| Tools | - | PainDETECT | Body map or fibromyalgia survey |
| Treatment | NSAIDs, opioids, surgery | Local/nerve-targeted | CNS-acting drugs, non-pharmacologic |
| Examples | OA, cancer pain, RA | Diabetic neuropathy, PHN, sciatica | Fibromyalgia, IBS, TMD, tension headache |
Treatment
A multimodal approach is essential. Opioids and NSAIDs have little evidence and are not recommended as primary therapy.
Non-pharmacologic (first-line)
- Aerobic exercise - most evidence-based intervention (reduces pain and fatigue; recent 2025 meta-analysis [PMID 39805734] supports individualized aerobic prescription)
- Cognitive Behavioral Therapy (CBT) - addresses maladaptive pain behaviors and central sensitization
- Patient education - understanding the CNS mechanism reduces catastrophizing
- Sleep hygiene and sleep-directed therapies
- Aquatic therapy, yoga, tai chi - especially for those who cannot tolerate land-based exercise
- A 2025 network meta-analysis [PMID 40319533] found mixed exercise approaches (aerobic + resistance) most effective for pain intensity in women
Pharmacologic
| Drug | Class | Evidence |
|---|---|---|
| Duloxetine (Cymbalta) | SNRI | FDA-approved; reduces pain and fatigue |
| Milnacipran (Savella) | SNRI | FDA-approved; effective for pain and function |
| Pregabalin (Lyrica) | α2δ calcium channel ligand | FDA-approved; improves pain and sleep |
| Amitriptyline (low dose) | TCA | Good evidence for sleep and pain; not FDA-approved for FM |
| Cyclobenzaprine | Muscle relaxant/TCA-like | Short-term benefit, especially for sleep |
| Tramadol | Weak opioid + SNRI | Limited use; avoid strong opioids |
NSAIDs and opioids are generally ineffective because fibromyalgia is a central pain disorder, not driven by peripheral inflammation or tissue damage.
Diet (emerging)
A 2025 systematic review [PMID 40576703] found that the Mediterranean diet, with anti-inflammatory and low-antigenic properties, may reduce fibromyalgia symptom burden, though evidence remains preliminary.
Fibromyalgia as a Comorbidity
When fibromyalgia coexists with inflammatory diseases (RA, axSpA):
- Disease activity scores (like ASDAS, DAS28) are artifactually elevated
- Response to biologics appears worse, but biologics still provide real benefit for underlying joint disease
- The comorbid fibromyalgia needs independent management - it will not respond to DMARDs or biologics
- Arthroplasty outcomes may be worse, but surgery still benefits underlying joint disease
Key Takeaway
Fibromyalgia is a real, biologically grounded condition - brain imaging, CSF analysis, and neurophysiology demonstrate objective abnormalities. It is best treated with therapies targeting the CNS: exercise, CBT, and SNRIs/alpha-2-delta ligands. Opioids worsen central sensitization over time and should be avoided.
Sources: Goldman-Cecil Medicine (26th ed.), p. 2885-2888 | Firestein & Kelley's Textbook of Rheumatology (11th ed.), p. 598 | Rheumatology 2-Volume Set (Elsevier, 2022)
Recent evidence: aerobic exercise meta-analysis (PMID 39805734) and network meta-analysis on exercise types (PMID 40319533) confirm non-pharmacologic therapies as cornerstone treatment.
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