Oral lichen planus possibly associated with Hashimoto's thyroiditis: A case-control study in a northwest Chinese population.

BACKGROUND/PURPOSE: Some studies have previously demonstrated possible association between Hashimoto's thyroiditis (HT) and oral lichen planus (OLP), however, data of immunity and inflammation in these patients were not well investigated. This study aimed to propose some novel findings based on a case-control study of 185 OLP patients and 185 age- and gender-matched non-OLP volunteers in northwest China. MATERIALS AND METHODS: This study was designed and implemented in a tertiary teaching hospital between January 2021 and December 2024. Comprehensive evaluation was performed including thyroid function tests and seroimmunological parameters. RESULTS: The incidence of HT among OLP patients reached 31.9 %, demonstrating a statistically significant elevation compared to the control group's prevalence of 9.7 % (P < 0.001). Regarding autoimmune markers, thyroid peroxidase antibody (TPO-Ab) positivity was observed in 18.9 % of OLP patients, significantly exceeding the 4.3 % rate in controls (P = 0.002). Gender-based analysis revealed that female patients had a markedly higher TPO-Ab positivity rate (21.99 %) compared to males (9.09 %) (P = 0.012). Clinical subtype analysis demonstrated that patients with erosive OLP lesions showed a significantly higher TPO-Ab positive rate (25.74 %) than those with reticular lesions (11.63 %) or atrophic lesions (9.76 %) (P = 0.028). Logistic regression modeling identified two significant risk factors: female OLP patients had an 8.935-fold increased risk of TPO-Ab positivity compared to males (P = 0.036), while patients with erosive lesions showed a 3.199-fold higher risk than non-erosive cases (P = 0.038). CONCLUSION: Our findings demonstrate a strong correlation between OLP, especially its erosive form, and thyroid autoimmunity, with female sex representing an independent and clinically relevant predisposing factor.