Fibromyalgia is a chronic functional neurosensory disorder of unknown etiology. The pathophysiology is notable for pervasive symptoms despite the absence of identifiable inflammation or structural changes on physical exam, imaging, or histology. Cardinal symptoms include diffuse chronic musculoskeletal pain, fatigue, and unrefreshing sleep. Cognitive dysfunction (often called fibro fog), headaches, and morning stiffness are also commonly reported. Individuals with fibromyalgia often have comorbid conditions with overlapping clinical features (e.g., depressive disorders, migraine, irritable bowel syndrome). Since objective findings cannot be used to confirm or rule out fibromyalgia, the diagnosis relies on a thorough history of symptoms (i.e., character, duration, and severity). Although fibromyalgia is not a progressive illness, it can cause significant functional limitations and distress. Step-wise treatment begins with patient education, especially pertaining to exercise for which there is strong evidence to support a therapeutic effect. Additional treatments (e.g., physiotherapy and pharmacological therapy) and multidisciplinary pain management can be considered using shared decision-making.
The pathophysiology of fibromyalgia is not fully understood; its etiology is likely multifactorial. The interaction of the following factors may play a role: 
- Genetic predisposition
- Autoimmune 
- Environmental triggers (e.g., physical or psychosocial stress)
- Dysregulation of the neuroendocrine and autonomic nervous systems
Fibromyalgia manifests with chronic functional symptoms. Symptoms and severity vary between individuals, ranging from mild and intermittent to persistent and disabling.
Cardinal symptoms of fibromyalgia 
Diffuse chronic musculoskeletal pain
- Distribution: all or most regions of the body
- Character: variable, often neuropathic, without objective pathologic findings
- Unrefreshing sleep
Common additional symptoms 
- Fibro fog: a form of cognitive dysfunction that includes difficulty concentrating and lack of clarity of thought
- Headaches (e.g., migraine)
- Morning stiffness
- Memory deficits
- Abdominal pain or cramps
- Autonomic changes
- Restless leg syndrome
- Pain at tender points; (used historically): 18 sites on the body, primarily where muscles and tendons attach to bone
The diagnosis of fibromyalgia is based on symptoms alone. Imaging studies and biomarkers (e.g., ESR) are typically normal.
Clinical evaluation 
- Consider the diagnosis in patients with cardinal symptoms of fibromyalgia (± fibro fog) for ≥ 3 months.
- Assess for:
- Baseline impact on quality of life and functional status
- Alleviating and aggravating factors (e.g., sensitivity to cold or noise)
- Order CBC and either ESR or CRP to identify a concomitant inflammatory condition. 
- Limit additional studies to specific conditions being considered, e.g: 
- Evaluation tools may help standardize the assessment but are not required for diagnosis.
Do not test patients for specific alternative conditions (e.g., Lyme disease) unless they have characteristic clinical features and appropriate history. 
Evaluation tools 
Numerous diagnostic criteria and validated tools for screening and assessment have been proposed but are not required for diagnosis.
- 2016 ACR diagnostic criteria
- Simplified Fibromyalgia Screening Questionnaire
- Advantage: standardized assessments
- Limitation: debated and uncertain clinical utility
Comorbid conditions 
Several conditions share prominent clinical features with fibromyalgia and often occur simultaneously, e.g.:
- Functional syndromes
- Inflammatory conditions
Fibromyalgia and conditions with overlapping symptoms are not mutually exclusive and can occur simultaneously. 
- See also “.”
Myofascial pain syndrome
- Definition: : a chronic pain syndrome caused by muscle tension, injury, or repetitive motion and characterized by the presence of trigger points in muscles and/or fascia (small tender knots) 
- Pain is mostly confined to one anatomical region: fewer tender points compared to fibromyalgia (≤ 11 of 18)
- Leads to weakness and limited range of motion
- Jump sign (myofascial pain syndrome): A physical examination finding characterized by an involuntary, sudden jerk or wince in response to stimulation of a tender area or trigger point (not seen in fibromyalgia).
- Fatigue, headache, and sleep disturbances are less frequent compared to fibromyalgia
- Treatment: physical therapy, massage, stretching, ice packs, NSAIDs
The differential diagnoses listed here are not exhaustive.
- Optimize patient education and supportive therapy for all patients.
- Consider adding pharmacotherapy for severe pain and/or sleep disturbance refractory to nonpharmacological measures.
- Engage a multidisciplinary team ; (e.g., rheumatology, psychiatry) for patients who do not achieve adequate relief.
- For patients with new, worsening, or changing pain seen in ambulatory and emergency settings:
- Follow the general approach to .
- Avoid repeating extensive diagnostic testing that has already been done (especially involving radiation or invasive procedures).
- Consult the patient's regular provider(s) early and arrange follow-up.
Patient education 
- Exercise: There is strong evidence to support the benefits of aerobic and strengthening exercises. 
- Reassurance: Fibromyalgia is not a progressive illness and does not result from muscle or nerve damage.
- Validation: Symptoms can be overwhelming and disabling.
- Coping strategies, e.g., relaxation techniques
- See also “Patient encounters” in “Managing chronic conditions.”
Supportive therapy 
- Physiotherapy (e.g., stretching, hydrotherapy, and heat application)
- Cognitive behavioral therapy
Pharmacological therapy 
- Severe pain: pregabalin and/or duloxetine and/or tramadol (off-label) 
- Sleep disturbance: low dose amitriptyline and/or cyclobenzaprine and/or pregabalin