COVID-19 and Oral Lichen Planus: Between an "Intriguing Plot" and the "Fata Morgana Effect".

The COVID-19 pandemic, caused by the SARS-CoV-2 virus, has led to significant morbidity and mortality worldwide since its declaration as a global pandemic in March 2020. Alongside the typical respiratory symptoms, unusual clinical manifestations such as oral lichen planus (OLP) have been observed. OLP is a chronic inflammatory mucocutaneous dermatosis that results from a cell-mediated reaction, and its pathogenesis involves the loss of immunological tolerance. OLP has been associated with several triggering factors, such as certain drugs, stress, smoking, and even some viruses. Exposure to the spike protein antigen of SARS-CoV-2 during an infection can trigger autoimmune reactions and lead to the onset or flare of OLP. The E3 protein ligase TRIM21, which is identified in the lamina propria of OLP lesions, is overexpressed in COVID-19 patients and plays a critical role in autoimmune pathologies. Furthermore, the psychological stress of the lockdown and quarantine can be a trigger for the onset or exacerbation of OLP. However, the diagnosis of OLP is complex and requires a biopsy in order to confirm a clinical diagnosis, rule out other pathologies, and establish the most appropriate therapeutic procedure. Further research is needed to understand the potential link between Co-19 and OLP.