Lichen Planus

Table of Contents

1. What Lichen Planus Is
2. Pathophysiology: T-Cell Attack on Basal Keratinocytes
3. Cutaneous Lichen Planus: The 5 P's
4. Oral and Genital Mucosal Lichen Planus
5. Clinical Variants: Hair, Nails, and Subtypes
6. Hepatitis C Association
7. Drug-Induced Lichenoid Reactions
8. Diagnosis: Clinical Signs and Histopathology
9. Malignant Potential of Oral and Vulvar LP
10. Treatment: Corticosteroids, Retinoids, and Immunosuppressants
11. Key Research Papers
12. Connections
13. Featured Videos

What Lichen Planus Is

Lichen planus (LP) is a chronic, relapsing, T-cell-mediated inflammatory disease that targets basal keratinocytes — the deepest layer of the epidermis. It can affect the skin, oral and genital mucous membranes, hair follicles (lichen planopilaris), and nails, either individually or in combination. The name comes from the Greek word for "tree moss" (λειχήν, lichen) and the Latin word "planus" (flat, planar) — describing the characteristic flat-topped papules of classic cutaneous LP.

Lichen planus affects approximately 0.5–2% of the population worldwide, with equal sex distribution for cutaneous LP. Oral lichen planus affects women more than men at roughly 2:1. A 2020 pooled analysis of 46 studies estimated oral lichen planus at 0.89% of the general population (95% confidence interval 0.38–2.05%), with 0.57% in Asia, 1.68% in Europe and 1.39% in South America in population-based studies, and 1.55% of women against 1.11% of men. In its clinic-based studies, 0.62% of patients under 40 had it and 1.90% of those 40 and older; the authors urge caution because the studies differ widely. Peak onset is typically between the fourth and sixth decades of life, though LP can occur at any age. It is rare in children.

The etiology remains incompletely understood — lichen planus is called "idiopathic" because no single trigger has been identified for most cases. However, immune-mediated attack on basal keratinocytes is the final common pathway, triggered in susceptible individuals by drugs, infections (notably hepatitis C virus), contact allergens, stress, or unknown factors. Understanding LP matters both for symptom control and because certain subtypes — particularly erosive oral LP and vulvar LP — carry a measurable risk of malignant transformation to squamous cell carcinoma.

Pathophysiology: T-Cell Attack on Basal Keratinocytes

Lichen planus is the prototypical example of a lichenoid tissue reaction — a pattern of immune-mediated basal keratinocyte destruction that can be reproduced by a variety of triggers. The fundamental immunological event is:

T-Cell Infiltration and Basal Cell Targeting

Activated CD4+ and CD8+ T lymphocytes migrate to the skin (or mucous membrane) and accumulate in a dense band immediately below the epidermis, targeting basal keratinocytes. CD8+ cytotoxic T cells in the basal layer directly kill keratinocytes via Fas-FasL interactions, perforin/granzyme-B release, and tumor necrosis factor alpha (TNF-α) secretion. Basal keratinocytes upregulate intercellular adhesion molecule 1 (ICAM-1) and present self-peptides or altered self-antigens (possibly modified by drugs, viral proteins, or contact allergens) on major histocompatibility complex (MHC) class I molecules — triggering recognition and killing by cytotoxic T lymphocytes.

Simultaneously, CD4+ helper T cells in the upper dermis produce interferon-gamma and tumor necrosis factor alpha, amplifying the inflammatory response and sustaining the infiltrate. The result is a characteristic band-like (lichenoid) mononuclear infiltrate hugging the dermo-epidermal junction — the signature of LP on histopathology.

Basal Cell Liquefaction

Killed basal keratinocytes undergo apoptosis, producing Civatte bodies (also called colloid bodies or eosinophilic bodies) — eosinophilic, ovoid apoptotic keratinocytes within or just below the epidermis. This is a diagnostic hallmark on skin biopsy. The destruction of the basal cell layer causes the characteristic histological sawtooth rete ridges — irregular, jagged elongations of the rete ridges that reflect the irregular basal cell destruction and compensatory proliferation pattern.

Melanin Incontinence

Damaged basal keratinocytes release melanin granules into the dermis, where they are engulfed by dermal macrophages (melanophages). This produces the clinically visible post-inflammatory hyperpigmentation — the dark brown or gray discoloration that persists for months to years after LP lesions resolve, particularly on darker skin types. This hyperpigmentation can be more distressing than the original lesions.

Why LP Favors Certain Sites

LP has a predilection for specific anatomical sites — wrists, shins, lower back (skin); buccal mucosa, tongue, gingiva (oral); vulva, glans penis (genital). The tissue-specific expression of basal keratinocyte antigens, the local immune microenvironment, and site-specific T-cell trafficking patterns likely explain the anatomical distribution. The Koebner phenomenon (LP developing in skin areas subjected to trauma) implies that localized trauma can trigger or amplify the T-cell response at that site.

Cutaneous Lichen Planus: The 5 P's

The classic cutaneous presentation of lichen planus is memorized by dermatology trainees with the mnemonic of the 5 P's:

• Pruritic — the lesions are typically intensely itchy, often disproportionately so relative to their appearance
• Polygonal — the papules have an irregular, multi-sided rather than round outline, giving them a characteristic geometric shape when examined closely
• Purple (violaceous) — the color ranges from pink to violaceous (blue-purple) to brown on lighter skin tones; on darker skin, lesions may appear hyperpigmented brown or gray rather than purple
• Planar (flat-topped) — unlike acne papules or nodules, LP papules have a distinctly flat top; dermoscopy reveals this clearly
• Papules — the primary lesion is a small, solid elevation of the skin (1–10 mm); papules can coalesce into plaques

Wickham's Striae

A pathognomonic surface feature of LP papules is Wickham's striae — a network of fine, white, lacy (reticulate) or linear lines visible on the surface of the papule when examined with a magnifying lens or dermoscope (after application of oil or water to the surface). Wickham's striae represent focal thickening of the granular layer of the epidermis (hypergranulosis) directly related to the immune-mediated changes in the epidermis above the lichenoid infiltrate. Their presence on skin papules is highly suggestive of LP.

Distribution of Cutaneous LP

Classic cutaneous LP has a predilection for:

• Flexor wrists — the most characteristic site; clusters of violaceous flat-topped papules on the inner wrist and forearm
• Shins and ankles — lower legs, where lesions may become hypertrophic (see Variants below)
• Lower back and sacral area
• Genitals — glans penis, vulva
• The face, palms, and soles are typically spared in classic cutaneous LP

Oral and Genital Mucosal Lichen Planus

Oral Lichen Planus

Oral LP (OLP) is common, with a pooled estimate of 0.89% of the general population (0.57–1.68% across continents), and may occur with or without cutaneous LP (many patients have isolated oral involvement). The classic presentation is bilateral white reticular (lacy, web-like) lines on the buccal mucosa — often described as a "fishnet" pattern. These reticular lesions are usually asymptomatic or mildly symptomatic and may be discovered incidentally.

However, OLP exists on a spectrum of severity:

• Reticular OLP: White lacy lines on the buccal mucosa (most common form; often asymptomatic; benign course)
• Papular OLP: White papules, often on the buccal mucosa or tongue
• Plaque OLP: Smooth white plaques resembling leukoplakia (biopsy is what separates the two)
• Erosive/ulcerative OLP: Painful irregular erosions or ulcers with surrounding reticular white lines; this form causes significant functional impairment (eating, speaking), has a chronic relapsing course, and carries malignant potential
• Atrophic OLP: Diffuse erythematous (red) areas, particularly on the gingiva ("desquamative gingivitis") — red, friable, easily bleeding gingiva that resembles severe gum disease but is immune-mediated
• Bullous/vesicular OLP: Rare; fluid-filled vesicles that rupture quickly leaving erosions

OLP characteristically shows bilateral symmetric involvement of the buccal mucosa (both cheeks affected simultaneously) — asymmetric or unilateral lesions raise suspicion for alternative diagnoses or malignant transformation.

Genital Lichen Planus

Genital LP is commonly underdiagnosed and can cause significant morbidity:

• Vulvar LP: Can manifest as reticular white striae on the labia minora (resembling oral reticular LP), or as erosive LP with painful red erosions of the vaginal introitus, labia, and vaginal mucosa. Erosive vulvar LP causes dyspareunia, dysuria, and vaginal discharge. Long-term scarring can produce architectural changes (loss of the labia minora, vaginal stenosis). Malignant potential to vulvar squamous cell carcinoma (VSCC) is established.
• Penile LP: Wickham's striae on the glans penis or ring-shaped (annular) lesions — typically less severe than vulvar LP; erosive penile LP is uncommon

Vulvo-vaginal-gingival syndrome (VVG syndrome) — the triad of erosive LP at all three sites simultaneously — is a well-recognized severe variant requiring aggressive systemic immunosuppression.

Clinical Variants: Hair, Nails, and Subtypes

Lichen Planopilaris (LPP) — Scalp and Hair

When lichen planus targets hair follicles, it causes lichen planopilaris (LPP) — a progressive scarring (cicatricial) alopecia. LPP presents with perifollicular erythema and scaling around hair follicles (follicular hyperkeratosis), follicular plugging, and progressive permanent hair loss as follicles are destroyed by the lichenoid infiltrate. Areas of alopecia show smooth, shiny atrophic skin without follicular openings (follicles permanently destroyed = no regrowth possible). Classic LPP involves the scalp vertex and crown; frontal fibrosing alopecia (FFA) — a variant of LPP — causes progressive frontal hairline recession and eyebrow loss, predominantly in postmenopausal women.

Nail Lichen Planus

LP can affect the nail matrix, nail bed, or both. Changes include:

• Longitudinal ridging and grooves (longitudinal striations)
• Nail plate thinning and fragility
• Onychorrhexis (longitudinal splitting)
• Dorsal pterygium (pterygium unguis) — a pathognomonic finding where the nail matrix is destroyed and the proximal nail fold fuses to the nail bed, forming a scar-tissue "wing" that permanently divides the nail. Dorsal pterygium is virtually specific to nail LP and cannot regrow once formed.

Nail LP can progress to permanent nail loss (anonychia) and requires early treatment to prevent irreversible nail matrix destruction.

Hypertrophic LP

Hypertrophic (verrucous) LP occurs predominantly on the shins and ankles — chronic LP lesions subjected to repeated scratching or trauma develop thick, hyperkeratotic, wart-like plaques up to several centimeters. These lesions are intensely pruritic and resistant to treatment; they may persist for decades. Long-standing hypertrophic LP on the shins carries a small but real risk of squamous cell carcinoma development within the plaques.

Other Cutaneous Variants

• Annular LP: Ring-shaped lesions with central clearing; common on the glans penis and male genitalia
• Linear LP: Lesions in a linear Blaschkoid distribution following lines of Blaschko; may represent somatic mosaicism
• Inverse LP: LP in flexural areas (axillae, groin, inframammary folds) rather than extensor surfaces
• Vesiculobullous LP: Blister formation within LP papules from severe basal cell destruction; rare
• Actinic LP: LP triggered by sun exposure; presents on sun-exposed areas; more common in Middle Eastern and Indian populations; lesions may have a melasma-like pigmentary component

Hepatitis C Association

The association between lichen planus (particularly oral LP) and hepatitis C virus (HCV) infection is one of the most consistent and replicated findings in LP epidemiology. A 2009 meta-analysis found 5.4 times higher odds of hepatitis C virus exposure in people with lichen planus than in study controls (95% confidence interval 3.5–8.3), and a 2016 meta-analysis of oral LP found 6.07 times higher odds (95% confidence interval 2.73–13.48). In the 2009 analysis the link was not significant in studies from South Asia, Africa or North America, nor in the isolated cutaneous type. The association is strongest in Mediterranean (Italian, Spanish) and Japanese populations; weaker in Northern European populations.

Proposed Mechanisms

• Direct viral trigger: hepatitis C virus proteins may alter self-antigens on basal keratinocytes (particularly in the oral mucosa, which may be exposed to viremia through mucosal lymphoid tissue), triggering cross-reactive T-cell responses that persist as LP
• Molecular mimicry: hepatitis C virus proteins share epitopes with keratinocyte self-proteins, generating T cells that cross-react with both hepatitis C virus and host basal cells
• Immune dysregulation: Chronic hepatitis C virus infection causes broad immune dysregulation (including Th1/Th17 polarization) that may lower the threshold for autoimmune skin reactions

Clinical Implications

Screening for hepatitis C with anti-HCV antibodies ± HCV RNA is described for people with newly diagnosed oral LP and for extensive cutaneous LP without an obvious trigger; the 2016 meta-analysis concludes that the association "emphasizes the importance of hepatitis C virus screening in oral lichen planus patients." If hepatitis C virus is identified and the patient is eligible for treatment, direct-acting antiviral (DAA) therapy for hepatitis C virus can result in improvement or even resolution of LP in some patients — providing both hepatological and dermatological benefit. This is distinct from most other LP cases where no modifiable trigger is found.

In a 2022 cohort study, all 18 people with hepatitis C and oral LP cleared the virus on direct-acting antivirals, and their mouth lesions improved over time, while 19 people with oral LP and no hepatitis C showed no significant change. One treated patient developed a squamous cell cancer of the tongue during treatment.

Drug-Induced Lichenoid Reactions

Many drugs can cause a lichenoid reaction — a skin eruption that is clinically and histologically indistinguishable from (or closely resembles) idiopathic LP. Drug-induced lichenoid reactions are sometimes called "lichenoid drug eruption" to acknowledge that they may have subtle distinguishing features (more eosinophils on histology, presence of parakeratosis, more widespread distribution, photodistribution).

Major Drug Classes Causing Lichenoid Reactions

• Antimalarials: Hydroxychloroquine, chloroquine, quinidine — among the most established causes of lichenoid drug eruptions; photodistributed involvement is a clue
• Gold salts: Used historically for rheumatoid arthritis; a classic cause of lichenoid eruptions and also oral LP-like stomatitis
• Thiazide diuretics: Hydrochlorothiazide, chlorothiazide; may produce photodistributed lichenoid reactions
• Angiotensin-converting enzyme inhibitors (ACE inhibitors): Captopril, enalapril — lichenoid reactions; captopril's thiol group may act as a hapten
• Beta-blockers: Propranolol, practolol; oral LP-like reactions
• Penicillamine: Classic cause of both LP and pemphigus-like reactions
• Immune checkpoint inhibitors: PD-1/PD-L1 inhibitors (pembrolizumab, nivolumab) cause lichenoid eruptions as immune-related adverse events; histologically identical to idiopathic LP
• Dental amalgam (mercury): Contact lichenoid reactions adjacent to amalgam restorations in the oral cavity — considered a contact hypersensitivity to mercury rather than systemic drug eruption; replacement of amalgam with composite may resolve adjacent oral LP lesions

The interval from drug exposure to lichenoid eruption ranges from weeks to years — a long latency that makes drug causation easy to overlook. Resolution of the eruption weeks to months after drug withdrawal confirms drug causation retrospectively.

Diagnosis: Clinical Signs and Histopathology

Clinical Diagnosis

Classic cutaneous LP on the flexor wrists or shins with the 5 P's features and Wickham's striae visible on dermoscopy can often be diagnosed clinically without biopsy. Similarly, bilateral symmetric reticular white lines on the buccal mucosa are clinically diagnostic of reticular OLP.

However, biopsy is essential when:

• The diagnosis is uncertain (plaque LP mimicking leukoplakia; erosive OLP mimicking malignancy)
• There is suspicion of malignant transformation (especially in erosive OLP or vulvar LP)
• Drug-induced lichenoid reaction needs to be separated from idiopathic LP
• Clinical response to treatment is absent (to reconsider diagnosis)

Histopathological Features

Biopsy of an LP papule shows the characteristic lichenoid tissue reaction pattern:

• Band-like lymphocytic infiltrate: A dense, well-defined ribbon of lymphocytes and histiocytes immediately below the epidermis (the "lichenoid infiltrate"), hugging the dermo-epidermal junction like a storm cloud beneath the epidermis
• Vacuolar degeneration of the basal cell layer: Vacuolization and destruction of the basal keratinocytes (the primary immune target)
• Sawtooth rete ridges: Irregular, pointed elongations of the rete ridges — described as "saw-tooth" or "zigzag" in morphology — resulting from basal cell destruction and regenerative acanthosis
• Civatte bodies (colloid bodies): Eosinophilic, ovoid apoptotic keratinocytes within or just below the epidermis (at the dermo-epidermal junction or papillary dermis); represent dead basal keratinocytes
• Hypergranulosis: Thickening of the granular layer (directly above areas of Wickham's striae)
• Melanin incontinence: Free melanin granules and melanophages in the upper dermis

Direct immunofluorescence (DIF) on LP biopsy shows non-specific immunoglobulin M (IgM) (and less commonly immunoglobulin G (IgG), immunoglobulin A (IgA), C3) deposits within Civatte bodies — a fibrillar, cytoid body pattern at the dermo-epidermal junction. This DIF pattern is suggestive of LP but not diagnostic or specific (unlike the patterns in pemphigus or bullous pemphigoid). Normal-appearing perilesional skin and linear basement membrane zone deposits (which would indicate bullous pemphigoid) are absent in LP.

Malignant Potential of Oral and Vulvar LP

The risk of squamous cell carcinoma (SCC) arising in LP lesions is an important reason for long-term surveillance and aggressive management of erosive forms.

Oral LP — Squamous Cell Carcinoma Risk

A 2019 meta-analysis of 82 studies (26,742 patients, oral LP and related lichenoid lesions) pooled the malignant transformation rate for oral LP to oral SCC at 1.14% (95% confidence interval 0.84–1.49), and a 2026 meta-analysis of 24 studies (13,143 patients) limited to oral LP with no dysplasia at diagnosis found 1.56% (95% confidence interval 1.14–2.12). Both are rates seen during study follow-up, not lifetime risks, and the 2019 authors conclude that rates are underestimated because of restrictive diagnostic criteria, inadequate follow-up and low-quality studies. The risk is not uniform across OLP subtypes:

• Erosive/atrophic OLP carries the highest transformation risk
• Reticular OLP (the most common form) has a much lower risk, potentially negligible
• Carcinoma arising in OLP most commonly involves the tongue, floor of mouth, and buccal mucosa
• Signs treated as urgent reasons for biopsy: development of an indurated area, irregular or raised surface, loss of bilaterality, rapid growth, or change in appearance within a known OLP lesion

The 2019 meta-analysis names who carries more of the risk: people with atrophic-erosive lesions (relative risk 4.09), lesions on the tongue (1.82), tobacco use (1.98) and alcohol use (2.28). Hepatitis C showed a relative risk of 4.46, just short of statistical significance (95% confidence interval 0.98–20.22, p = 0.053).

The World Health Organization (WHO) classifies OLP as a "potentially malignant oral disorder" — placing it in the same category as leukoplakia and erythroplakia as conditions followed with ongoing surveillance. Reviews every 6–12 months by an oral medicine specialist or oral surgeon are the schedule described for all patients with OLP, not only erosive forms.

The classification itself is debated. A 2025 review sets out the disputes over diagnostic criteria, over whether dysplasia excludes the diagnosis, and over how to read reticular lesions and white plaques, and concludes that the evidence still supports treating OLP as a potentially malignant disorder.

Vulvar LP — VSCC Risk

Erosive vulvar LP is increasingly recognized as a precursor to vulvar squamous cell carcinoma (VSCC) through a human papillomavirus-independent pathway. Unlike the more common human papillomavirus-related VSCC (which arises from vulvar intraepithelial neoplasia), LP-associated VSCC arises from differentiated vulvar intraepithelial neoplasia (dVIN) in the context of chronic inflammatory atypia. Published figures for vulvar LP run from about 2% to 5%, with significant uncertainty given the rarity of long-term prospective data, and they are rates seen during follow-up rather than lifetime risks. A 2008 cohort found 1 vulvar carcinoma in 113 women with erosive vulvar LP over an average of 5 years; a 2026 cohort found 4 in 77 women (5.19%) over a mean of 45 months, all 4 in LP with superimposed lichen sclerosus or lichen simplex chronicus. The follow-up described for women with erosive vulvar LP is regular gynecological examination, with biopsy of new, indurated, or persistently non-healing erosions.

A 2026 review of 10 studies (15,829 patients) of lichen planus outside the mouth pooled the cancer rate at 1%: 2% for vulvar disease and 0% for skin disease. The erosive and hypertrophic forms were the ones most often linked with cancer.

Treatment: Corticosteroids, Retinoids, and Immunosuppressants

A 1998 evidence review of 83 clinical trials and small series found no large randomized trials with definitive results for any lichen planus treatment: only 3 small randomized trials with uncertain results (1 of acitretin in skin LP, 2 of topical corticosteroids in mucosal LP), the rest observational, and many expert recommendations resting on personal experience. That review called acitretin the first-line therapy for skin LP and topical corticosteroids the first-line therapy for erosive mucosal LP. The current European guidance is the 2020 S1 guideline of the European Dermatology Forum with the European Academy of Dermatology and Venereology.

First-Line: Topical Corticosteroids

High-potency topical corticosteroids are the cornerstone of LP treatment for both cutaneous and mucosal forms:

• Cutaneous LP: Clobetasol propionate 0.05% cream or ointment applied to affected skin twice daily. For hypertrophic lesions, occlusion under plastic wrap enhances penetration. Typically applied for 2–4 weeks, then tapered or used intermittently.
• Oral LP: Clobetasol 0.05% gel applied directly to oral lesions 2–3 times daily; triamcinolone acetonide in an adhesive oral paste for smaller discrete lesions. Systemic absorption from oral mucosal application is limited; keeping the gel from being swallowed is part of how it is used.
• Vulvar LP: Clobetasol 0.05% ointment applied to the affected area; maintenance therapy with weaker topical steroids to prevent architectural scarring progression.

Intralesional Corticosteroids

Intralesional triamcinolone acetonide (5–10 mg/mL) injected directly into resistant skin plaques (particularly hypertrophic LP on the shins) or into oral LP lesions can achieve local disease control when topical therapy fails. Intralesional injection for nail LP (targeting the nail matrix) may prevent progression to dorsal pterygium formation.

Topical Calcineurin Inhibitors

Tacrolimus 0.1% ointment and pimecrolimus 1% cream are effective steroid-sparing alternatives, particularly for mucosal LP:

• Tacrolimus 0.1% ointment is particularly useful for erosive OLP and erosive vulvar LP — well-tolerated on mucosal surfaces, without the atrophogenic risk of long-term topical steroid use
• Also useful for facial LP and intertriginous areas where prolonged high-potency steroid use causes skin atrophy
• Note: The FDA boxed warning on topical calcineurin inhibitors is not specific to lichen planus. It states that long-term safety has not been established and that, although a causal relationship has not been established, rare cases of malignancy (for example skin and lymphoma) have been reported. The labels cover atopic dermatitis only, so use in lichen planus is off-label. For areas already at risk for LP-associated SCC, the clinical significance remains debated

Systemic Therapy for Extensive or Refractory LP

• Oral corticosteroids (prednisone): For rapidly spreading, generalized, or severely symptomatic cutaneous LP, a short course of prednisone (0.5–1 mg/kg/day tapered over 4–6 weeks) can induce remission. Not suitable for long-term use given side effects.
• Acitretin (oral retinoid): Indicated for extensive cutaneous LP unresponsive to topical therapy and for mucosal LP. Acitretin modulates keratinocyte differentiation and has anti-inflammatory effects on the lichenoid infiltrate. Typical dose 25–50 mg/day. Main limitations: teratogenicity (strict pregnancy prevention required; 3-year washout after stopping), mucocutaneous dryness, hypertriglyceridemia. Effective particularly for hypertrophic LP and lichen planopilaris.
• Cyclosporine: For severe, refractory, erosive oral LP unresponsive to topical therapy; cyclosporine oral rinse (can be used topically in the mouth) has also been used for OLP. Systemic cyclosporine (2.5–5 mg/kg/day) is reserved for the most severe refractory cases given nephrotoxicity and hypertension risk.
• Narrowband UVB (NB-UVB) phototherapy: Effective for generalized cutaneous LP; 2–3 sessions per week for 2–3 months. Not appropriate for mucosal LP.
• Hydroxychloroquine: For actinic LP and some cases of oral LP; paradoxically, antimalarials can also cause lichenoid reactions, requiring careful consideration in individual cases.
• Mycophenolate mofetil, azathioprine: For refractory LP requiring long-term systemic immunosuppression as steroid-sparing agents.
• Tofacitinib and baricitinib (JAK inhibitors): Emerging evidence for refractory LP, particularly lichen planopilaris (LPP/FFA); multiple case series showing benefit; clinical trials underway. In a 2026 assessor-blind randomized trial, 32 people with skin LP took baricitinib 4 mg once daily or hydroxychloroquine 200 mg twice daily for 12 weeks: the disease score fell from 14.20 to 1.07 on baricitinib and from 12.18 to 5.27 on hydroxychloroquine (P = 0.03), and the itch score from 8.33 to 0.21 and from 8.81 to 3.27. The physician global assessment did not differ between groups (P = 0.38). The authors caution that the trial was small, short and not double-blind.

Key Research Papers

Key peer-reviewed studies on lichen planus pathogenesis, oral LP malignancy risk, hepatitis C association, and treatment. Each PMID link opens the study on PubMed.

1. Sugerman PB, et al. The pathogenesis of oral lichen planus. Crit Rev Oral Biol Med. 2002;13(4):350-365. — PubMed PMID: 12191961
2. van der Waal I. Potentially malignant disorders of the oral and oropharyngeal mucosa; terminology, classification and present concepts of management. Oral Oncol. 2009;45(4-5):317-323. — PubMed PMID: 18674954
3. Gandolfo S, et al. Risk of oral squamous cell carcinoma in 402 patients with oral lichen planus: a follow-up study in an Italian population. Oral Oncol. 2004;40(1):77-83. — PubMed PMID: 14662419
4. Carrozzo M, Thorpe R. Oral lichen planus: a review. Minerva Stomatol. 2009;58(10):519-537. — PubMed PMID: 19893476
5. Cribier B, Frances C, Chosidow O. Treatment of lichen planus. An evidence-based medicine analysis of efficacy. Arch Dermatol. 1998;134(12):1521-1530. — PubMed PMID: 9875189
6. Shengyuan L, et al. Hepatitis C virus and lichen planus: a reciprocal association determined by a meta-analysis. Arch Dermatol. 2009;145(9):1040-1047. — PubMed PMID: 19770446
7. Regezi JA, Sciubba JJ, Jordan RC. Oral Pathology: Clinical Pathologic Correlations. 7th ed. 2017. PubMed: Oral LP histopathology
8. Ioannides D, Vakirlis E, Kemeny L, et al. European S1 guidelines on the management of lichen planus: a cooperation of the European Dermatology Forum with the European Academy of Dermatology and Venereology. J Eur Acad Dermatol Venereol. 2020;34(7):1403-1414. — PubMed PMID: 32678513
9. Colafemina ACE, Pedroso CM, Perez-de-Oliveira ME, et al. Malignant Transformation in Extraoral Lichen Planus: A Systematic Review and Meta-Analysis in the Context of the Risk in Oral Lichen Planus. Dent J (Basel). 2026;14(4). — PubMed PMID: 42041670
10. Kennedy CM, Peterson LB, Galask RP. Erosive vulvar lichen planus: a cohort at risk for cancer? J Reprod Med. 2008;53(10):781-784. — PubMed PMID: 19004404
11. Pasquali MF, Dominoni M, Musacchi V, et al. Retrospective Study of the Risk of Progression to Squamous Cell Carcinoma of Vulvar Lichen Planus Forms Isolated or Associated With Other Dermatoses. J Obstet Gynaecol Res. 2026;52(3):e70248. — PubMed PMID: 41856763
12. Tziotzios C, et al. Lichen planus and lichenoid dermatoses: clinical overview and molecular basis. J Am Acad Dermatol. 2018;79(5):789-804. — PubMed PMID: 30318136
13. Li C, Tang X, Zheng X, et al. Global Prevalence and Incidence Estimates of Oral Lichen Planus: A Systematic Review and Meta-analysis. JAMA Dermatol. 2020;156(2):172-181. — PubMed PMID: 31895418
14. Alaizari NA, Al-Maweri SA, Al-Shamiri HM, Tarakji B, Shugaa-Addin B. Hepatitis C virus infections in oral lichen planus: a systematic review and meta-analysis. Aust Dent J. 2016;61(3):282-287. — PubMed PMID: 26475515
15. Di Stasio D, Lucchese A, Romano A, Adinolfi LE, Serpico R, Marrone A. The clinical impact of direct-acting antiviral treatment on patients affected by hepatitis C virus-related oral lichen planus: a cohort study. Clin Oral Investig. 2022;26(8):5409-5417. — PubMed PMID: 35477818
16. González-Moles MÁ, Ruiz-Ávila I, González-Ruiz L, Ayén Á, Gil-Montoya JA, Ramos-García P. Malignant transformation risk of oral lichen planus: A systematic review and comprehensive meta-analysis. Oral Oncol. 2019;96:121-130. — PubMed PMID: 31422203
17. Domingues CB, Botelho J, Azul AM, Trancoso PF. Malignant potential of oral lichen planus without epithelial dysplasia: a systematic review and meta-analysis of longitudinal studies. Front Oncol. 2026;16:1949729. — PubMed PMID: 42947806
18. González-Moles MÁ, Ramos-García P. Malignant transformation of oral lichen planus: where are we now? Med Oral Patol Oral Cir Bucal. 2025;30(1):e65-e75. — PubMed PMID: 39396138
19. Kargar H, Esfandiari MA, Ghahartars M, Parvizi MM. Baricitinib vs. hydroxychloroquine for cutaneous lichen planus: an assessor-blind randomized controlled trial. Clin Exp Dermatol. 2026;51(10):1865-1873. — PubMed PMID: 42161332

Curated PubMed topic searches:

1. PubMed: LP T-cell pathogenesis
2. PubMed: OLP malignant transformation
3. PubMed: LP and hepatitis C
4. PubMed: Lichen planopilaris alopecia
5. PubMed: Drug lichenoid eruptions
6. PubMed: LP topical treatment
7. PubMed: Vulvar LP and VSCC
8. PubMed: Acitretin for LP

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Connections

• Dermatology
• Pemphigus Vulgaris
• Bullous Pemphigoid
• Stevens-Johnson Syndrome
• Psoriasis
• Eczema
• Alopecia
• Contact Dermatitis
• Vitiligo
• Lupus
• Hepatitis C
• Seborrheic Dermatitis

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