The exact pathogenesis of LP remains uncertain; however, it is postulated that keratinocyte damage occurs through CD8+ cytotoxic T-cell-mediated apoptosis following antigen presentation by basal keratinocytes. A deficiency in TGF-β1-mediated immunosuppression may lead to sustained overactivity of these cytotoxic T cells, contributing to the chronicity of the disease. ^{1, 2}

Accurate epidemiologic data on LP are limited. A systematic review and meta-analysis conducted in September 2019 reported a global pooled prevalence of LP at 1.01% with significant geographical variation. ³ Due to the lack of robust, large-scale epidemiologic data specifically on cutaneous LP, we have used published data on oral LP as a proxy for estimating prevalence. We acknowledge this limitation, and an interim analysis is planned to validate the prevalence assumptions within our study population.

Currently, the diagnosis of lichen planus relies primarily on clinical evaluation, including assessment of the “6P’s” (planar, purple, polygonal, pruritic, papules and plaques) and distribution that commonly affects the skin of the flexor surfaces. The presence of Wickham striae, which are prominent, lacy, reticular white lines, is considered diagnostic. However, differential diagnoses such as Prurigo, Lupus Erythematosus, erythema dyschromicum perstans, psoriasis, secondary syphilis, pityriasis rosea, lichen nitidus, graft versus host disease, and keratosis lichenoides chronica must be ruled out, often necessitating histopathological confirmation via excisional biopsy. ^{4, 5}

Dermoscopy enhances the visualisation of subtle skin changes that are not apparent to the naked eye, thereby revolutionising the diagnosis of inflammatory dermatoses. Dermoscopic patterns have been shown to correlate with histopathological features; for example, Wickham striae (WS) reflect focal thickening of the stratum granulosum, while red dots indicate vascular changes. ^{6– 9}

Histologically, LP is characterised by hyperkeratosis (typically orthokeratosis), acanthosis, and irregular thickening of the stratum granulosum (hypergranulosis) resulting in the “saw-tooth” appearance of the rete ridges. Basal cell liquefaction leads to the formation of apoptotic keratinocytes (Civatte or cytoid bodies) and the development of a cleft (Max Joseph space). A dense band-like lymphocytic infiltrate (interface dermatitis) is observed at the dermo-epidermal junction, sometimes accompanied by a few plasma cells, and in drug-induced cases, eosinophils. ^{4, 10– 12}

Dermoscopy offers an attractive adjunct to reduce the need for invasive biopsies. UVFD, by providing additional optical data (through penetration, absorption, scattering, and Stokes-shift phenomena), may further enhance diagnostic accuracy. ^{13– 16}

Although some literature suggests that UVFD may be less effective than non-contact polarised dermoscopy in diagnosing LP, we hypothesise that its integration will improve diagnostic accuracy by revealing both specific and non-specific features that correlate with histopathological findings. For instance, loose keratin may appear as white lines and compact keratin plugs as yellow clods on conventional dermoscopy, whereas UVFD may reveal white fluorescence in both, confirming keratin’s natural fluorescence. In early-stage disease, when vascular structures are not distinctly visible as red dots or clods, UVFD may delineate them as dark structureless areas at the lesion periphery. Accordingly, an additional rationale for this study is to document both specific and non-specific UVFD features and correlate them with polarised dermoscopy and histopathological findings. ^{13, 17, 18}

1.

Correlation between dermoscopic and histopathological findings may be challenging because dermoscopy provides an axial surface view, whereas histopathology provides a cross-sectional tissue view. ^{23, 24}

This study is expected to clarify the diagnostic utility of dermoscopy and ultraviolet-induced fluorescence dermoscopy in cutaneous lichen planus and to identify imaging features that correlate with histopathological findings. By exploring both conventional dermoscopic patterns and UVFD-derived observations, this protocol may contribute to the development of more refined non-invasive diagnostic approaches for lichen planus. The study’s prospective design and planned clinicodermoscopic-histopathological correlation are strengths, although its single-centre setting may limit generalisability. The findings may also provide preliminary data to inform future multicentre validation studies.

This study has been approved by the Institutional Ethics Committee of Datta Meghe Institute of Higher Education and Research, Wardha, Maharashtra, India (study approval number: DMIHER (DU)/IEC/2024/141; IEC Re-reg. No. ECR/440/Inst/MH/2013/RR-2019) in December 2023. Written informed consent will be obtained from all participants before enrolment into the study. Separate written consent will be obtained for the use of clinical images where applicable. The study will be conducted in accordance with the ethical principles of the Declaration of Helsinki.

Clinical Trials Registry–India (CTRI): CTRI/2025/05/086296; Reference No. REF/2024/03/080873. Registered on 05/05/2025 URL: https://ctri.nic.in/Clinicaltrials/regtrial.php?modid=1&compid=19&EncHid=71931.98915

The study findings will be disseminated through publication in peer-reviewed journals and presentation at academic conferences.

Image analysis will be performed using ImageJ and QuPath. Statistical analysis will be conducted using R version 4.3.2. These are publicly available software tools. No custom source code was generated or used for this study protocol.

During manuscript preparation, the authors used OpenAI ChatGPT (GPT-5.4 Thinking), Google Gemini 3.1 Pro, and Grammarly (Superhuman Go, running on OpenAI’s GPT-4.1 family) solely to improve the English language, enhance readability, and cross-check journal author guidelines. These tools were not used for data generation, statistical analysis, interpretation of findings, or scientific decision-making. All generated suggestions were critically reviewed and edited by the authors, who take full responsibility for the final manuscript content.