Does PMR Cause Elevated CRP and ESR?
Yes, Polymyalgia Rheumatica (PMR) typically causes elevation in both ESR and CRP, though importantly, normal inflammatory markers do not exclude the diagnosis.
Typical Laboratory Findings
Both ESR and CRP are usually elevated in PMR, with ESR being raised (>30 mm/h) in the vast majority of cases and CRP elevated (>6 mg/l) in approximately 89% of patients at presentation 1.
The EULAR/ACR guidelines mandate measurement of both ESR and/or CRP as part of the basic laboratory dataset prior to initiating therapy, recognizing these as key inflammatory markers for diagnosis and monitoring 2.
ESR appears to be the preferred marker for long-term disease monitoring and has stronger prognostic value, with high ESR (>40 mm/1st hour) being specifically associated with higher relapse rates and need for prolonged therapy 3, 2.
The Critical Exception: PMR with Normal Inflammatory Markers
Approximately 7-22% of PMR patients present with normal or only slightly elevated ESR at diagnosis, and this subset is well-recognized in the literature 4, 5, 6.
Normal ESR and CRP do not exclude PMR or GCA, and current EULAR/ACR guidelines explicitly state that clinical presentation takes precedence over laboratory values 7.
PMR with normal inflammatory markers is considered an atypical presentation that warrants specialist referral according to EULAR/ACR guidelines 2, 8.
Distinguishing Features of Low ESR/CRP PMR
Patients with PMR and normal inflammatory markers have specific characteristics:
- Younger age at diagnosis compared to typical PMR patients 5, 6.
- Longer diagnostic delay before treatment initiation 4, 5.
- Longer symptom duration before diagnosis 6.
- Lower frequency of constitutional symptoms such as fever or weight loss 5.
- Lower comorbidity rates 6.
Alternative Inflammatory Markers
When ESR and CRP are normal, serum amyloid A (SAA) may be elevated and can serve as an alternative acute phase reactant 6.
Imaging modalities (ultrasound demonstrating bursitis, MRI, or FDG-PET/CT) can support the diagnosis when inflammatory markers are normal 9, 6.
Clinical Implications for Diagnosis
The diagnosis of PMR should be based on clinical presentation, not solely on laboratory values. Key diagnostic approach:
- Measure both ESR and CRP as part of initial workup 2.
- If clinical presentation is consistent with PMR but markers are normal, do not exclude the diagnosis 7, 9.
- Consider additional testing including SAA, imaging studies, and comprehensive laboratory panel to exclude mimicking conditions 7, 6.
- Refer to rheumatology for atypical presentations including low inflammatory markers 2, 7.
Monitoring Considerations
ESR is generally the better indicator of clinical disease activity during treatment and follow-up 1.
During relapses, ESR may be normal in 48% of cases and CRP in 56%, so clinical assessment remains paramount 1.
Both markers should be monitored during follow-up as they may become elevated during disease flares even if initially normal 8.