Fibromyalgia vs Polymyositis and Dermatomyositis
Fibromyalgia and Polymyositis and Dermatomyositis are easy to mix up on the boards. Here's a side-by-side comparison — presentation, workup, imaging, and first-line treatment — drawn from our full outlines.
Fibromyalgia vs Polymyositis and Dermatomyositis at a glance
- Fibromyalgia: Centralized pain syndrome with widespread tenderness, fatigue, and sleep and cognitive disturbance; normal labs and imaging.
- Polymyositis and Dermatomyositis: Idiopathic inflammatory myopathies causing symmetric proximal muscle weakness; dermatomyositis adds skin findings.
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Side-by-side comparison
| Feature | Fibromyalgia | Polymyositis and Dermatomyositis |
|---|---|---|
| At a glance | Centralized pain syndrome with widespread tenderness, fatigue, and sleep and cognitive disturbance; normal labs and imaging. | Idiopathic inflammatory myopathies causing symmetric proximal muscle weakness; dermatomyositis adds skin findings. |
| Classic presentation | Diffuse musculoskeletal pain >3 months in multiple body regions, often migratory; Profound fatigue, especially morning fatigue and after exertion;… | Middle-aged woman with several months of progressive symmetric proximal weakness, a violaceous (heliotrope) rash over the upper eyelids, and Gottron papules… |
| Workup / key labs | 2016 ACR criteria: widespread pain index (WPI) and symptom severity scale (SSS) — pain in 4 of 5 body regions for ≥3 months with WPI ≥7 and SSS ≥5 (or WPI 4-6… | Bohan and Peter criteria (historic) and EULAR/ACR 2017 criteria. Classic features include symmetric proximal weakness, elevated muscle enzymes, characteristic… |
| Imaging | Generally NOT indicated — incidental findings on MRI commonly mislead; Image only if focal red-flag findings emerge (true weakness, focal joint signs,… | MRI of affected muscles — T2 hyperintensity reflecting edema; guides biopsy site; High-resolution chest CT for interstitial lung disease, particularly if… |
| First-line treatment | Patient education — emphasize that pain is real, reflects altered central pain processing, and is not destructive or progressive; Aerobic exercise — graded,… | High-dose corticosteroids — prednisone 1 mg/kg/day (up to 60-80 mg) until objective improvement, then taper over 9-12 months; Methylprednisolone pulses for… |
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