Polymyalgia rheumatica (PMR) and rheumatoid arthritis (RA) are both inflammatory conditions that can cause joint pain and stiffness, but they have key differences in presentation, pathology, and management.
Key Differences Between Polymyalgia Rheumatica and Rheumatoid Arthritis
| Feature | Polymyalgia Rheumatica (PMR) | Rheumatoid Arthritis (RA) |
|---|---|---|
| Onset | Sudden or subacute | Gradual and insidious |
| Age Group | >50 years (usually >70) | Any age, but common 30–50 |
| Gender | More common in women | More common in women |
| Symptoms | Proximal muscle pain and stiffness (shoulders, hips, neck) | Symmetric joint pain, swelling, and morning stiffness (>1 hour) |
| Morning Stiffness | >45 minutes | >1 hour |
| Joint Involvement | Large joints, no erosions | Small joints (MCP, PIP, wrists), erosions seen on imaging |
| Systemic Symptoms | Fatigue, weight loss, low-grade fever | Fatigue, weight loss, low-grade fever |
| Giant Cell Arteritis (GCA) Association | Common (15–20% have GCA) | Not associated |
| Autoantibodies | None | RF and anti-CCP often positive |
| ESR/CRP | Markedly elevated | Elevated but variable |
| Imaging | MRI/ultrasound: bursitis, synovitis | X-ray: joint space narrowing, erosions |
| Response to Steroids | Dramatic response to low-dose prednisone | Partial response to steroids |
| Treatment | Corticosteroids (low dose) | DMARDs (methotrexate, biologics) |
Clinical Pearls
- PMR: Predominantly affects proximal muscles, causes stiffness but no true weakness, and has a dramatic response to corticosteroids.
- RA: Affects small joints first, causes erosive arthritis, and requires long-term DMARDs to prevent joint damage.
Would you like a case-based comparison for better understanding?
Case-Based Comparison: Polymyalgia Rheumatica (PMR) vs. Rheumatoid Arthritis (RA)
Case 1: Polymyalgia Rheumatica (PMR)
Patient: 72-year-old woman
Presentation:
- Symptoms: Sudden onset of shoulder and hip stiffness, particularly severe in the morning, lasting over an hour. Difficulty raising arms to comb hair or getting out of bed. Mild fatigue and low-grade fever. No swelling in small joints (hands or feet).
- Labs:
- ESR: 70 mm/hr (elevated)
- CRP: Elevated
- RF and anti-CCP: Negative
- Imaging: MRI shows bursitis in shoulders and hips, no joint erosions.
- Treatment: Started on low-dose prednisone (10-20 mg daily). Symptoms improve dramatically within 48 hours.
- Diagnosis: Polymyalgia Rheumatica
Key Points:
- Rapid response to low-dose steroids is a hallmark.
- Common in older adults (>50 years).
- Often associated with Giant Cell Arteritis (GCA)—look for headache, scalp tenderness, and jaw claudication.
Case 2: Rheumatoid Arthritis (RA)
Patient: 45-year-old woman
Presentation:
- Symptoms: Gradual onset of pain and swelling in both hands, affecting the metacarpophalangeal (MCP) and proximal interphalangeal (PIP) joints symmetrically. Morning stiffness lasting more than an hour. Fatigue and mild weight loss.
- Labs:
- ESR: Elevated
- CRP: Elevated
- RF: Positive
- Anti-CCP: Positive
- Imaging: X-ray shows joint space narrowing and early erosions in MCP joints.
- Treatment: Started on methotrexate, later added a biologic agent. Symptoms improved gradually over weeks.
- Diagnosis: Rheumatoid Arthritis
Key Points:
- RA affects small joints symmetrically with erosive changes.
- Positive RF and anti-CCP are supportive but not required for diagnosis.
- Requires DMARDs for long-term management to prevent joint destruction.
Clinical Application
- PMR is considered when elderly patients have severe proximal stiffness with a rapid steroid response.
- RA should be suspected in adults of any age presenting with symmetric small joint arthritis, especially with positive serologies and erosions.
These cases illustrate the diagnostic distinctions and treatment approaches for PMR and RA. Let me know if you want more details or have other questions!
Simon Downes, MD, PhD 