What is Polymyalgia Rheumatica (PMR)?
Polymyalgia rheumatica is an inflammatory rheumatic disease affecting adults over 50 years of age, characterized by bilateral proximal pain and morning stiffness in the shoulders, neck, and pelvic girdle, accompanied by elevated inflammatory markers. 1, 2
Clinical Characteristics
PMR presents with specific features that distinguish it from other conditions:
- Bilateral proximal aching and morning stiffness affecting the neck, shoulders, upper arms, lower back, hips, and thighs 3
- Age requirement: Only occurs in individuals over 50 years of age, with most cases appearing after age 60 1, 2
- Gender predilection: 2-3 times more common in women, who also face higher risk of glucocorticoid side effects 2, 1
- Onset pattern: May be acute or develop over a few days to weeks 4
- Systemic symptoms: Fatigue, fever, and weight loss commonly occur, driven by systemic IL-6 signaling 4
Underlying Pathology
The disease involves:
- Synovial and periarticular inflammation affecting the shoulder and pelvic girdle regions 4
- Muscular vasculopathy contributing to the pain syndrome 4
- Intense systemic inflammatory response reflected in laboratory markers 2
Laboratory Findings
PMR is characterized by:
- Elevated inflammatory markers: C-reactive protein (CRP) and/or erythrocyte sedimentation rate (ESR) are typically elevated 5
- High ESR (>40 mm/1st hour) at baseline is associated with higher relapse rates and prolonged therapy 1, 6
Key Diagnostic Considerations
When evaluating suspected PMR, you must exclude mimicking conditions:
- Rheumatoid arthritis: Obtain rheumatoid factor and/or anti-cyclic citrullinated peptide antibodies (ACPA) 5
- Giant cell arteritis (GCA): PMR may be the first manifestation of GCA, requiring painstaking search for other signs 7
- Elderly-onset rheumatoid arthritis (EORA): A chief mimicker that must be differentiated 2
- Other conditions: Inflammatory myositis, vasculitis, malignancy, infections, endocrine disorders, and drug-induced syndromes (particularly from immune checkpoint inhibitors) 5, 2, 4
Atypical Presentations Requiring Specialist Referral
Consider referral when encountering:
- Peripheral inflammatory arthritis (associated with higher relapse rates) 1, 6
- Systemic symptoms beyond typical PMR presentation 5
- Low inflammatory markers despite clinical symptoms 5
- Age <60 years 1, 5
- Immune checkpoint inhibitor-induced PMR-like syndromes: Can present with severe myalgia in proximal upper extremities, sometimes without significant lower extremity involvement 5
Treatment Response
PMR is highly responsive to glucocorticoid therapy:
- Prompt response to 15-25 mg prednisolone daily is characteristic 4
- Failure to respond should suggest giant cell arteritis, malignant disease, or infection 7
- Relapse rate: Estimated at 50% of patients while tapering glucocorticoid doses 2
Disease Burden
PMR is the second most frequent inflammatory rheumatic disease in people aged over 50 years, after rheumatoid arthritis 8. The condition causes significant morbidity, particularly from glucocorticoid-related complications including diabetes and osteoporosis, as treatment often exceeds 1 year 2, 8.