Fibromyalgia

Overview

•Chronic centralised pain disorder - widespread musculoskeletal pain, fatigue, and cognitive difficulties with NO identifiable inflammatory or structural pathology

•Mechanism: central sensitisation - heightened CNS excitability causing allodynia and hyperalgesia; disorder of pain processing, not primary muscle/joint disease

•Women ~10x more affected; typical age 20-50 years

Presentation

•Widespread pain - chronic (>3 months), bilateral, above and below waist, axial skeleton; aching/burning/stabbing

•Unrefreshing sleep - wakes unrestored despite adequate hours

•Fatigue - profound and persistent

•'Fibro fog' - concentration, memory, and word-finding difficulties

•Paraesthesias, headaches, mood disturbance (anxiety/depression), widespread tenderness on palpation

•Examination: characteristically normal - no muscle weakness, no joint swelling, no synovitis, no neurological deficit

Investigations

•Clinical diagnosis - investigations exclude mimics

•FBC, ESR, CRP - expected normal in fibromyalgia; raised ESR/CRP prompts alternative diagnosis

•TFTs - exclude hypothyroidism (close mimic)

•Creatine kinase - normal in fibromyalgia; raised in inflammatory myopathy

•Rheumatoid factor, anti-CCP, ANA - if RA or SLE suspected

🎯

Normal ESR and CRP is a key discriminating feature from polymyalgia rheumatica (ESR typically >40 mm/hr) - this distinction is frequently tested.

Diagnostic criteria

•ACR 2010 criteria - all three must be met:

•WPI ≥7 and SSS ≥5 OR WPI 3-6 and SSS ≥9

•Symptoms present for at least 3 months

•No other disorder adequately explains the symptoms

•Fibromyalgia can coexist with other conditions (e.g. RA, SLE) - ~25% of RA patients and ~50% of SLE patients also meet fibromyalgia criteria

Management

•First-line (non-pharmacological): aerobic exercise - single most effective treatment; improves pain, fatigue, and quality of life

🥇 First-line

•patient education (central sensitisation model) and cognitive behavioural therapy (CBT)

•First-line pharmacological: amitriptyline (low-dose TCA at night) - improves sleep and reduces central pain sensitisation

•Duloxetine (SNRI) - useful when depression/anxiety is significant comorbidity

•Pregabalin or gabapentin (gabapentinoids) - reduce neuronal excitability; effective for pain and sleep

⚠️

Opioids and long-term NSAIDs should be avoided - opioids worsen central sensitisation (opioid-induced hyperalgesia); NSAIDs target peripheral inflammation which is absent in fibromyalgia.