Serum Calprotectin Concentration in Patients with Oral Lichen Planus: A Cross-Sectional Study

Background and Objectives: Oral lichen planus (OLP) is a mucocutaneous autoimmune disease with a complex aetiology and an entirely unknown pathophysiological mechanism. Calprotectin (CP) is an inflammation-related protein and a potential biomarker of disease activity. This study aimed to examine the association between serum calprotectin (sCP), disease duration, and disease activity in patients with erosive (active) and non-erosive (inactive) OLP. Materials and Methods: This cross-sectional study included 50 participants: 30 patients with OLP (20 erosive, 10 non-erosive) and 20 healthy controls. Medical and dental histories, sociodemographic data, disease duration, and OLP activity assessed by the Oral Lichen Planus Disease Activity Scale (OLP-DAS) were recorded, along with inflammatory markers [C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), lactate dehydrogenase (LDH), and sCP]. Results: Non-erosive OLP patients had a statistically significantly higher sCP concentration than erosive patients (2.32 μg/mL vs. 1.34 μg/mL, p = 0.018). The area under the curve (AUC) was 43.9% in OLP patients (p = 0.470). There were no statistically significant differences between OLP patients and controls for ESR (p = 0.878), CRP (p = 0.439), or LDH (p = 0.476). There was a weak negative correlation between sCP concentration and disease duration in erosive (r₁ = -0.115, p₁ = 0.629) and non-erosive OLP (r₂ = -0.166, p₂ = 0.647). There was a moderate, negative, statistically significant correlation between sCP concentration and OLP-DAS (r = -0.455, p = 0.012). Conclusions: The findings of this study indicate that OLP inflammation is primarily local and chronic, rather than systemic. Serum CP showed limited diagnostic and prognostic value.