Fibromyalgia: Diagnosis and Management

Introduction

Fibromyalgia is a chronic pain syndrome characterised by widespread musculoskeletal pain, profound fatigue, unrefreshing sleep and cognitive difficulty, in the absence of any demonstrable inflammatory, structural or metabolic cause. It is now understood as a disorder of central pain processing - central sensitisation and abnormal descending pain modulation - rather than a disease of the joints or muscles themselves.¹

It commonly coexists with other conditions with a similar central-sensitisation mechanism, including irritable bowel syndrome, chronic fatigue syndrome, migraine, temporomandibular joint dysfunction and interstitial cystitis, and frequently overlaps with anxiety and depression.

It is examined for a specific reason: the diagnostic approach (clinical, pattern-based, with normal investigations) and the treatment approach (exercise and psychological support first, avoiding opioids and NSAIDs) both run counter to the instinct to chase and treat an inflammatory cause, and testing that judgement is exactly the point.

Aetiology and pathophysiology

The precise mechanism remains incompletely understood, but functional imaging and other studies point to central sensitisation: an amplified central nervous system response to normal sensory input, so that stimuli that would not normally be painful are perceived as painful (allodynia), and painful stimuli are perceived as more painful than expected (hyperalgesia).

• Female sex - commoner in women, though the gap has narrowed since diagnostic criteria moved away from tender point counting
• Genetic predisposition - a degree of familial clustering is recognised
• Psychological stress and trauma - can act as a trigger, though fibromyalgia is not simply a psychiatric condition
• Sleep disturbance - both a cause and a consequence, creating a self-perpetuating cycle
• Coexisting chronic pain conditions - a history of another central sensitisation syndrome (IBS, chronic fatigue syndrome) increases risk
• Physical or emotional trauma, and some infections, have been proposed as triggers in a subset of patients

Clinical features

• Chronic widespread pain, present for more than 3 months, affecting both sides of the body, above and below the waist, and often the axial skeleton
• Profound fatigue, often out of proportion to activity
• Unrefreshing sleep - waking tired despite adequate sleep duration
• Cognitive difficulty ('fibro fog') - problems with concentration, word-finding and short-term memory
• Diffuse tenderness on examination, without objective synovitis, swelling, or weakness
• Associated symptoms - headache, irritable bowel symptoms, paraesthesiae, restless legs, temperature dysregulation, and low mood or anxiety

Differential diagnosis

Because fibromyalgia has no diagnostic test, other explanations for widespread pain and fatigue need to be actively considered and excluded, particularly at first presentation:

• Inflammatory arthritis (rheumatoid arthritis, other connective tissue disease) - look for objective synovitis and raised inflammatory markers
• Polymyalgia rheumatica - in an older patient with proximal pain and a raised ESR/CRP, unlike the normal markers of fibromyalgia
• Hypothyroidism - fatigue and diffuse aching, checked with TFTs
• Inflammatory myopathy - a raised CK points away from fibromyalgia
• Vitamin D deficiency - a common and easily treated contributor to diffuse musculoskeletal pain
• Chronic fatigue syndrome - substantial symptomatic overlap; the two frequently coexist
• Depression and anxiety disorders - can present with fatigue and somatic pain, and commonly coexist with fibromyalgia rather than being a simple alternative diagnosis
• Hypermobility spectrum disorder / Ehlers-Danlos syndrome - joint hypermobility with chronic pain, worth considering particularly in younger patients

Investigations

Fibromyalgia is a clinical diagnosis. Investigations are used to exclude other conditions, not to confirm fibromyalgia itself, and should be targeted rather than an exhaustive screen repeated at every visit.

• FBC, CRP/ESR - normal in fibromyalgia; abnormal results should prompt investigation for an inflammatory or infective cause
• TFTs - to exclude hypothyroidism
• Creatine kinase - normal; excludes a myopathic cause of pain and weakness
• Vitamin D - deficiency is common and treatable, and can mimic or worsen fibromyalgia-type symptoms
• Further serology or imaging - only where specific clinical features (objective synovitis, weight loss, neurological signs) suggest an alternative diagnosis, not as a routine part of fibromyalgia work-up

Management

Management is built around a biopsychosocial model, addressing physical, psychological and sleep components together, with medication playing a supporting rather than a central role.²

Core, non-pharmacological treatment

• Patient education - explaining central sensitisation in accessible terms, and validating that the pain is real even though investigations are normal, is itself a meaningful part of treatment
• Graded aerobic exercise - the intervention with the strongest evidence base; started gently and built up gradually, since too rapid an increase can worsen symptoms and undermine engagement
• Cognitive behavioural therapy (CBT) or acceptance and commitment therapy (ACT) - helps patients manage the impact of chronic pain on function and mood
• Sleep hygiene measures, given how central unrefreshing sleep is to the symptom complex
• Multidisciplinary pain management programmes, combining physiotherapy, psychology and occupational therapy

Pharmacological treatment

NICE's chronic pain guidance (NG193) classifies fibromyalgia as a form of chronic primary pain and is explicit that paracetamol, NSAIDs, opioids and corticosteroids should not be started for it, given the lack of proven benefit and the real risk of harm, particularly dependence with long-term opioid use.³

• Low-dose amitriptyline - commonly used off-label, particularly for pain and sleep
• Duloxetine - an SNRI antidepressant with evidence for pain in fibromyalgia
• Pregabalin - used off-label in the UK, with evidence for pain reduction, though sedation and weight gain limit tolerability for some patients
• Medication is generally considered as an adjunct to the non-pharmacological programme above, not as first-line treatment on its own

Complications

Fibromyalgia itself does not cause structural joint or organ damage, but its impact on quality of life, work, relationships and mental health can be substantial, and depression and anxiety are common, bidirectional companions. Poorly managed expectations - repeated investigation seeking a structural cause, or reflexive analgesic escalation including opioids - can cause iatrogenic harm without benefit, which is why clear communication about the diagnosis early on matters as much as any specific treatment.

Red flags

Prognosis

Fibromyalgia is a chronic condition that tends to fluctuate rather than resolve completely, but many patients achieve meaningful improvement in symptoms and function with a sustained exercise programme, psychological support and appropriate expectation-setting. Outcomes are generally better where the diagnosis is made and explained early, avoiding a prolonged, anxiety-provoking search for an alternative structural cause.