The Role of Immature Granulocytes in Fibromyalgia: An Indicator of Subclinical Inflammation?

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Background: Fibromyalgia (FM) is a chronic musculoskeletal disorder characterized by widespread body pain and various symptoms. Its etiology remains unclear to date. It has been associated with various pathogenic mechanisms, primarily inflammation. Immature granulocytes (IGs) have been proposed as a potential biomarker, playing a role in both inflammatory responses and prognosis in numerous diseases. No other study has investigated the count of immature granulocytes (IG#) and percentage of immature granulocytes (IG%) in FM patients. The aim of this study is to investigate the IG# and IG% in FM patients and to evaluate the relationship between these parameters and disease parameters. Methods: This retrospective observational study included 95 patients diagnosed with FM and 63 healthy control subjects matched for body mass index and gender. Biochemical, hematological parameters, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) and other inflammatory markers were recorded for both groups. Fibromyalgia Survey Diagnostic Criteria and Severity Scale (FSDC) and Fibromyalgia Impact Questionnaire (FIQ) scores were recorded for FM patients. Results: In FM patients, the IG% and IG# were significantly higher than in the healthy control group (p < 0.001, p: 0.006, respectively). There was no significant difference between the CRP and ESR values of the two groups. The platelet large cell count (PLCC) was significantly lower in the FM group (p < 0.032). Conclusions: IG levels can be used as a systemic early, sensitive, and low-cost marker in patients with FM. Based on our current knowledge, and considering the heterogeneous nature of FM, IG levels may serve as a meaningful tool in identifying subgroup elements reflecting an inflammatory phenotype. However, these findings require further validation through larger sample size, prospective studies, and advanced analyses including cytokine levels.