Expression of toll-like receptor 9 and human herpes virus 7 in lichen planus

Background Lichen planus (LP) is an inflammatory disease of unknown aetiology in which a viral cause or viral trigger has been suggested. Toll-like receptors (TLRs) have recently emerged as key sensors of invading microbes, with TLR9 being expressed inplasmacytoid dendritic cells, which are suggested to be elevated in association with viral infections such as human herpes virus 7 (HHV7). Objective The objective of this study was to evaluate tissue expression of TLR9 mRNA and HHV7 DNA in the skin lesions of patients with LP and to investigate whether a relation exists between them. Patients and methods In this case control study, skin biopsies were taken from lesional skin of 30 patients with LP and from 30 normal individuals as controls for detection of TLR9 mRNA using reverse transcriptase PCR and HHV7 DNA using PCR. Results This study showed significantly higher LR9 mRNA levels in lesional skin than in control skin (Po0.001). HHV7 DNA was positive in 16 patients (53.3%), whereas it was negative in all the controls, and the difference was statistically significant (Po0.001). HHV7-positive patients showed higher mean TLR9 mRNA values when compared with HHV7-negative patients, but no significant relation was detected between them(P = 0.339). Conclusion HHV7 and TLR9 may play a role in the pathogenesis of LP.