Can Polymyalgia Rheumatica (PMR) cause elevated White Cell Count (WCC) and neutrophils?

Polymyalgia Rheumatica and Elevated White Cell Count

Polymyalgia rheumatica (PMR) can cause elevated white cell count (WCC) and neutrophils, reflecting the inflammatory nature of the disease rather than indicating an infection. 1, 2

Laboratory Findings in PMR

PMR typically presents with several characteristic laboratory abnormalities:

• Elevated inflammatory markers:
  • Erythrocyte sedimentation rate (ESR)
  • C-reactive protein (CRP)
  • Leukocytosis (elevated WCC) 1, 2
  • Neutrophilia (elevated neutrophil count) 1, 2
  • Thrombocytosis (elevated platelet count) 2
  • Decreased hemoglobin (anemia of inflammation) 1

Research has demonstrated that untreated PMR patients show significant increases in leukocytes and neutrophils compared to healthy controls 1. This myeloid shift (increased neutrophils and monocytes) is a hallmark of the inflammatory response in PMR 2.

Mechanism of Neutrophil Activation in PMR

The elevated neutrophil count in PMR is not merely a numerical increase but reflects functional activation:

• Immune complex-mediated neutrophil activation occurs via FcγRIIA receptors 3
• Increased levels of neutrophil activation markers (CD66b, CD11b) 3
• Elevated plasma calprotectin (a neutrophil activation marker) 3
• Increased neutrophil extracellular traps (NETs) 3

Diagnostic Implications

When evaluating a patient with suspected PMR who has elevated WCC and neutrophils:

1. Basic laboratory dataset should be obtained as recommended by EULAR/ACR guidelines 4:

   • Complete blood count (will show the elevated WCC and neutrophils)
   • ESR and/or CRP (typically markedly elevated)
   • Rheumatoid factor and anti-CCP antibodies (to exclude RA)
   • Liver function tests, creatinine, glucose
   • Bone profile (calcium, alkaline phosphatase)

2. Consider additional tests to exclude mimicking conditions 4, 5:

   • Thyroid function tests
   • Creatine kinase (to exclude inflammatory myopathies)
   • Protein electrophoresis (to exclude paraproteinemia)
   • Antinuclear antibodies and ANCA (if other autoimmune diseases suspected)

Clinical Correlation

The elevated WCC and neutrophils in PMR should be interpreted in the context of:

• Age >60 years
• Bilateral shoulder and/or hip girdle pain
• Morning stiffness >45 minutes
• Rapid response to low-dose glucocorticoids (15-20 mg/day prednisone) 5

Treatment Effect on WCC and Neutrophils

Treatment with glucocorticoids typically results in:

• Rapid reduction in inflammatory markers
• Normalization of leukocyte and neutrophil counts 1
• Improvement in clinical symptoms within 24-72 hours 5

However, research suggests that a myeloid profile (elevated monocytes and neutrophils) may persist even during treatment and in treatment-free remission, possibly reflecting ongoing subclinical inflammation 2.

Pitfalls and Caveats

• Differential diagnosis: Elevated WCC and neutrophils can also indicate infection, which must be excluded before attributing these findings to PMR 4
• Monitoring: Regular follow-up (every 4-8 weeks in first year) should include assessment of inflammatory markers 4
• Treatment response: Failure of WCC and neutrophils to normalize with appropriate glucocorticoid therapy should prompt reconsideration of the diagnosis

PMR represents more of an inflammatory disease than an autoimmune disease, with the myeloid lineage playing a significant role in its pathophysiology 1, 6. The elevated WCC and neutrophils are consistent with this inflammatory profile and should normalize with appropriate treatment.