Ten cases of severe oral lichen planus showing granular C3 deposition in oral mucosal basement membrane zone

Background Oral lichen planus (OLP) may show depositions of immunoglobulins and complement components in oral mucosal basement membrane zone (BMZ) in direct immunofluorescence, although these finding are not frequently seen. Objective We collected and examined ten cases of severe OLP showing granular C3 deposition in BMZ. Materials and Methods In addition to clinical, histopathological and direct immunofluorescence assessments, we performed various immuneserological tests, including indirect immunofluorescence of normal human skin and 1M NaCl-split skin, immunoblotting of normal human epidermal and dermal extracts, recombinant proteins of BP180 NC16a and C-terminal domains, concentrated culture supernatant of HaCaT cells and purified human laminin-332, and enzyme-linked immunosorbent assays for BP230 and BP180. Results Direct immunofluorescence showed C3 deposition in BMZ exclusively of granular pattern in 7 cases and of both granular and linear patterns in 3 cases. The 10 cases showed no positive reactivity for either IgG or IgA antibodies in any immunoserological tests. Detailed analyses of clinical, histopathological and immunological findings revealed striking female prevalence, although other parameters were in general characteristic of OLP. Conclusions Granular C3 deposition in oral BMZ may be one of the characteristic features of severe OLP, although mechanisms for C3 deposition and its pathogenic role in OLP are currently unknown.