What are the diagnostic criteria and treatment options for Polymyalgia Rheumatica (PMR)?

Polymyalgia Rheumatica Diagnosis

Diagnose PMR based on age >50 years, bilateral shoulder and hip girdle pain with morning stiffness, elevated inflammatory markers (ESR/CRP), and exclusion of mimicking conditions through comprehensive laboratory testing, followed by a therapeutic trial of prednisone 12.5-25 mg daily. 1, 2

Diagnostic Algorithm

Step 1: Clinical Criteria Assessment

• Age requirement: Patient must be >50 years old; age <60 years is considered atypical and mandates specialist referral 3
• Pain pattern: New-onset bilateral shoulder pain with or without pelvic girdle involvement (pelvic girdle pain is not mandatory for diagnosis) 4, 5
• Morning stiffness: Pronounced stiffness, particularly in shoulder and hip regions 6, 7
• Functional impairment: Difficulty with activities of daily living due to pain and stiffness 5
• Onset: Acute or subacute development over days to weeks 7

Step 2: Core Laboratory Testing (Mandatory Before Treatment)

Obtain the following baseline tests to exclude mimicking conditions 1, 2:

• Inflammatory markers: ESR and/or CRP (typically elevated in >90% of cases; ESR >40 mm/hr associated with higher relapse rates) 2, 5
• Autoantibodies: Rheumatoid factor and/or anti-CCP antibodies to exclude rheumatoid arthritis 1, 2, 4
• Complete blood count: Assess for anemia and other causes of inflammation 2
• Metabolic panel: Glucose, creatinine, liver function tests (establishes baseline before glucocorticoid therapy) 1, 2
• Bone profile: Calcium and alkaline phosphatase (assesses bone health before steroids) 1, 2
• Urinalysis: Dipstick to exclude inflammatory or infectious conditions 1, 2

Step 3: Additional Recommended Testing

Consider these tests based on clinical presentation 1, 2:

• Protein electrophoresis: Excludes paraproteinemia 2
• TSH: Rules out thyroid disorders 2
• Creatine kinase: Excludes myopathies and myositis 2
• Vitamin D: Establishes baseline before glucocorticoid therapy 2

Step 4: Extended Testing for Atypical Presentations

Order when other autoimmune conditions are suspected 1, 2:

• ANA and ANCA: When vasculitis or other autoimmune diseases are considered 1, 2
• Tuberculosis testing: Before immunosuppressive therapy or in high-risk patients 2
• Chest radiograph: Excludes malignancy and other diagnoses 1, 2

Step 5: Imaging (Optional but Increasingly Useful)

• Ultrasound: Detects bilateral subdeltoid bursitis in 69% of PMR patients, improving diagnostic accuracy 5
• MRI: Can localize inflamed tissues in shoulder and hip regions 6
• PET-CT: Shows systemic inflammation but limited by cost and availability 7

Critical Exclusion of Mimicking Conditions

Before confirming PMR diagnosis, systematically exclude 1, 3:

• Inflammatory arthritis: Rheumatoid arthritis (check RF/anti-CCP), spondyloarthropathy, RS3PE syndrome
• Vasculitis: Giant cell arteritis (check for headache, visual symptoms, jaw claudication), other systemic vasculitides
• Endocrine disorders: Thyroid disease, diabetes
• Infections: Tuberculosis, endocarditis
• Malignancies: Particularly in patients with constitutional symptoms, weight loss, or atypical presentations
• Drug-induced: Checkpoint inhibitor therapy can cause PMR-like syndromes 4
• Other: Myopathy (true weakness vs. pain-related limitation), chondrocalcinosis, SLE

Mandatory Specialist Referral Situations

Refer immediately to rheumatology for 2, 3, 4:

• Age <60 years (highly atypical presentation)
• Peripheral inflammatory arthritis
• Systemic symptoms (significant weight loss, fever)
• Low or normal inflammatory markers despite typical symptoms
• High risk of glucocorticoid-related side effects
• Atypical features that don't fit classic PMR pattern

Therapeutic Trial as Diagnostic Tool

• Initial dose: Prednisone 12.5-25 mg daily (use higher end of range for patients with high relapse risk and low adverse event risk) 1, 4, 5
• Expected response: Dramatic improvement within days to 1 week in true PMR 5, 6
• Caveat: Response to steroids is NOT pathognomonic—other conditions (malignancy, infection, other inflammatory diseases) can also respond to glucocorticoids, so do not use response as sole diagnostic criterion 3

Common Diagnostic Pitfalls

• Do not diagnose PMR in patients <50 years old; this age cutoff is absolute 3, 7
• Do not rely solely on steroid response for diagnosis—many serious conditions respond to glucocorticoids 3
• Do not skip comprehensive laboratory workup even if clinical presentation seems classic—mimicking conditions must be excluded 1, 2
• Do not assume normal inflammatory markers exclude PMR, but recognize this as atypical and warrants specialist evaluation 3
• Do not overlook giant cell arteritis symptoms (headache, visual changes, jaw claudication)—PMR and GCA are associated in up to 20% of cases 5, 7

Assessment of Comorbidities Before Treatment

Document baseline status of 1, 4:

• Hypertension, diabetes, glucose intolerance, cardiovascular disease
• Dyslipidemia, peptic ulcer disease
• Osteoporosis (particularly recent fractures)
• Cataracts or glaucoma risk factors
• Chronic or recurrent infections

Follow-Up Schedule

• Frequency: Every 4-8 weeks during the first year of treatment 4
• Monitoring: Inflammatory markers, symptoms, glucocorticoid side effects, disease activity

Prognostic Factors

Risk factors for relapse include 4:

• Female sex
• High ESR (>40 mm/hr at baseline)
• Peripheral inflammatory arthritis