Dermatology · PANCE / PANRE

Lichen Planus

Written & clinically reviewed by Ryan Busch, PA-C · Updated August 2026 · Report an error

Idiopathic T-cell mediated inflammatory dermatosis with pruritic violaceous polygonal papules and characteristic Wickham striae.

Also known as: lichen planus, LP, oral lichen planus, lichen planopilaris

Overview

An idiopathic, T-cell mediated inflammatory disorder affecting skin, mucous membranes, hair, and nails, characterized by the '6 P's': pruritic, planar (flat-topped), purple, polygonal, papules and plaques.

Epidemiology

Affects ~1% of adults; peak ages 30-60. Slight female predominance. Oral lichen planus affects 1-2% of adults, often without skin involvement.

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Question 1DermatologyMedium
A 42-year-old woman presents with a 6-week history of an intensely itchy rash. Examination reveals clusters of flat-topped, violaceous, polygonal papules on the flexor surfaces of both wrists and the ankles, several arising along a linear scratch mark. Fine, lacy white lines are visible on the surface of the papules under side lighting. Inspection of the mouth shows reticular white striations on the buccal mucosa bilaterally. Which of the following is the most likely diagnosis?
  • ALichen planus
  • BPityriasis rosea
  • CPsoriasis
  • DSecondary syphilis
Reveal answer & full explanation
Correct answer: A — Lichen planus
  • ALichen planus✓
  • BPityriasis rosea
  • CPsoriasis
  • DSecondary syphilis

Why Lichen planus is correct

  • The vignette shows the classic "6 P's": pruritic, planar (flat-topped), purple (violaceous), polygonal papules on the flexor wrists and ankles.
  • The fine lacy white lines on the papule surface are Wickham striae, which are essentially pathognomonic for lichen planus when seen with side lighting or dermoscopy.
  • Reticular white striations on the buccal mucosa indicate oral lichen planus, which frequently accompanies cutaneous disease.
  • Lesions appearing along a scratch mark demonstrate the Koebner phenomenon, also characteristic of lichen planus.

Why the others are wrong

  • Psoriasis — well-demarcated plaques with thick silvery scale on extensor surfaces (elbows, knees, scalp) and nail pitting; lesions are not violaceous, lack Wickham striae, and do not produce buccal reticular striae.
  • Pityriasis rosea — a self-limited eruption with a herald patch followed by salmon-colored oval plaques in a "Christmas tree" distribution on the trunk; lesions are non-violaceous and spare the oral mucosa.
  • Secondary syphilis — generalized papulosquamous eruption that characteristically involves the palms and soles, with mucous patches, lymphadenopathy, and condylomata lata; it lacks Wickham striae, and serology (RPR/FTA) is positive.
Question 2DermatologyMedium
A 52-year-old woman presents with a 6-week history of an intensely itchy rash on both wrists and ankles. On exam, there are clusters of violaceous, flat-topped, polygonal papules over the flexor surfaces of the wrists, with fine reticulated white lines visible on the surface of several lesions under side lighting. She also reports a burning sensation in her mouth, and white lacy streaks are seen on the buccal mucosa bilaterally. A punch biopsy shows a band-like lymphocytic infiltrate at the dermoepidermal junction with saw-toothed rete ridges. Which of the following is the most appropriate additional diagnostic test?
  • AAntinuclear antibody
  • BHepatitis C serology
  • CRapid plasma reagin
  • DDesmoglein antibody
Reveal answer & full explanation
Correct answer: B — Hepatitis C serology
  • AAntinuclear antibody
  • BHepatitis C serology✓
  • CRapid plasma reagin
  • DDesmoglein antibody

Why Hepatitis C serology is correct

  • The vignette is classic lichen planus: the 6 P's (pruritic, planar, purple, polygonal papules) with Wickham striae on the surface, plus reticular oral mucosal involvement and confirmatory band-like interface histology with saw-toothed rete ridges.
  • Hepatitis C is the strongest documented systemic association with lichen planus, and HCV antibody screening is recommended in patients with lichen planus—particularly those with widespread or oral involvement—because detecting and treating HCV is meaningful and the testing is low-risk.

Why the others are wrong

  • Antinuclear antibody — used to work up discoid lupus erythematosus, which can mimic LP but presents as photo-distributed annular scarring plaques with follicular plugging; the biopsy and Wickham striae here already establish LP, so ANA is non-discriminating.
  • Rapid plasma reagin — screens for secondary syphilis, which causes copper-colored palmoplantar macules, lymphadenopathy, and condyloma lata, not violaceous polygonal papules with interface dermatitis on histology.
  • Desmoglein antibody — positive in pemphigus vulgaris (intraepidermal acantholysis with flaccid bullae); for erosive/mucosal LP, direct immunofluorescence (shaggy fibrinogen at the basement membrane zone) is used to exclude pemphigus/pemphigoid, but circulating desmoglein serology is not the appropriate next test in this classic, biopsy-confirmed case.
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Risk factors

  • Hepatitis C infection (strongest association, especially in Mediterranean and Asian populations)
  • Medications (lichenoid drug eruption): thiazides, ACE inhibitors, beta-blockers, NSAIDs, antimalarials, gold, allopurinol, immune checkpoint inhibitors (anti-PD-1)
  • Contact allergens (dental amalgam → oral LP)
  • Stress
  • Autoimmune disease (alopecia areata, vitiligo, ulcerative colitis, myasthenia gravis)

Pathophysiology

Autoreactive CD8+ T-cells target basal keratinocytes expressing altered self-antigens, triggering apoptosis (Civatte/colloid bodies). Dense band-like lymphocytic infiltrate at the dermal-epidermal junction with vacuolar interface change, wedge-shaped hypergranulosis, and saw-toothed rete ridges.

Clinical presentation

Symptoms

  • Intense pruritus (skin LP) — patients rub rather than scratch (limits excoriation)
  • Painful oral or genital erosions — burning, dysphagia, dyspareunia
  • Scalp pain or itching with progressive hair loss (lichen planopilaris)

Signs / physical exam

  • Cutaneous: pruritic, planar (flat-topped), purple, polygonal papules with fine white reticulated lines (Wickham striae) on surface; flexor wrists, forearms, ankles, lower back, shins
  • Koebner phenomenon (lesions at sites of trauma)
  • Hyperpigmentation on resolution, especially in skin of color
  • Oral: reticular white striae on buccal mucosa (most common, asymptomatic); erosive form with painful ulcers (premalignant)
  • Genital: vulvovaginal-gingival syndrome (erosive vulvovaginal + oral LP); penile annular violaceous papules
  • Nail: longitudinal ridging/grooves, thinning, pterygium formation (scarring), anonychia
  • Scalp (lichen planopilaris): scarring alopecia with perifollicular erythema and scale; frontal fibrosing alopecia variant (postmenopausal women, recession of frontotemporal hairline)

Classic findings

Wickham striae (fine reticulated white lines on papule surface); violaceous polygonal flat-topped papules on wrists/ankles; reticular white striations on buccal mucosa.

Differential diagnosis

  • Lichenoid drug eruption — More widespread, photo-distributed, less oral involvement; resolves after offending drug withdrawn
  • Psoriasis — Silvery scale on extensor surfaces; nail pitting; not violaceous
  • Discoid lupus erythematosus — Photo-distributed annular plaques with follicular plugging, scarring; ANA may be positive
  • Pityriasis rosea — Herald patch followed by 'Christmas tree' pattern on trunk; non-violaceous; self-limited
  • Secondary syphilis — Palmoplantar copper macules, lymphadenopathy, condyloma lata; positive RPR/FTA
  • Oral candidiasis (mucosal LP DDx) — White plaques that wipe off; KOH or culture positive; immunosuppression
  • Oral leukoplakia / SCC — White plaque that does not wipe off; biopsy to exclude dysplasia/cancer
  • Graft-versus-host disease (chronic) — Post-HSCT; lichenoid skin and oral changes; multi-organ involvement

Diagnostic workup

Diagnostic criteria

Clinical + histopathologic confirmation; DIF in mucosal cases.

Labs

  • Hepatitis C antibody screening (strong recommendation in endemic areas and high-risk patients)
  • Skin biopsy: hyperkeratosis, wedge-shaped hypergranulosis, saw-toothed rete ridges, band-like lymphocytic infiltrate, Civatte bodies
  • Direct immunofluorescence (DIF) for mucosal/erosive disease: shaggy fibrinogen at BMZ, IgM-positive cytoid bodies — helps distinguish from pemphigus/pemphigoid

Imaging

  • Not indicated

Diagnostic algorithm

SiteTypical LesionFirst-Line Therapy
Cutaneous (wrists, ankles, shins)Pruritic violaceous polygonal papules with Wickham striaeHigh-potency topical steroid (clobetasol)
Oral (reticular)Asymptomatic white reticular striae on buccal mucosaObservation; oral hygiene
Oral (erosive)Painful ulcers, gingivitisTopical clobetasol gel, dexamethasone rinse, topical tacrolimus
GenitalErosive vulvovaginal-gingival syndrome; penile papulesTopical clobetasol/tacrolimus; vaginal dilators
Scalp (LPP, FFA)Scarring alopecia, perifollicular erythemaTopical/IL steroid + hydroxychloroquine ± 5ARI
NailsLongitudinal grooves, pterygiumIL triamcinolone in nail matrix; systemic if severe
Lichen planus variants and first-line therapy.

Treatment

First-line

  • Cutaneous LP (limited): high-potency topical corticosteroid (clobetasol 0.05%) BID 2-4 weeks
  • Topical calcineurin inhibitors (tacrolimus 0.1%, pimecrolimus 1%) for mucosal, genital, intertriginous areas — steroid-sparing
  • Antihistamines for pruritus (hydroxyzine, cetirizine)
  • Oral LP (reticular asymptomatic): observation; good oral hygiene
  • Oral LP (erosive): topical clobetasol gel, dexamethasone elixir swish-and-spit, or topical tacrolimus 0.1%; intralesional triamcinolone for refractory ulcers

Widespread / refractory cutaneous LP

  • Oral prednisone 30-60 mg/day tapered over 4-6 weeks (relapse common)
  • Phototherapy: narrowband UVB or PUVA
  • Oral acitretin 25-35 mg/day (teratogenic)
  • Methotrexate, mycophenolate, hydroxychloroquine, or sulfasalazine as steroid-sparing

Lichen planopilaris / frontal fibrosing alopecia

  • High-potency topical corticosteroid + intralesional triamcinolone
  • Hydroxychloroquine 200 mg BID (mainstay)
  • Oral 5-alpha reductase inhibitor (finasteride, dutasteride) for frontal fibrosing alopecia
  • Doxycycline, mycophenolate, JAK inhibitors as second-line

Second-line / adjunct

  • Dapsone, retinoids, oral cyclosporine, apremilast in refractory cases
  • Discontinue suspected drug if lichenoid drug eruption (improvement may take months)
  • Monitor erosive oral and genital LP for SCC transformation

Complications

  • Post-inflammatory hyperpigmentation (months to years)
  • Scarring alopecia (lichen planopilaris, frontal fibrosing alopecia)
  • Nail pterygium and permanent nail loss (anonychia)
  • Vulvovaginal scarring with introital stenosis
  • Squamous cell carcinoma in chronic erosive oral/genital LP (~1-3% lifetime risk) — surveillance biopsies
  • Sleep disruption from pruritus, depression

PANCE pearls

  • Remember the 6 P's: Pruritic, Planar, Purple, Polygonal, Papules, Plaques.
  • Wickham striae on lesion surface are pathognomonic — examine with side lighting or dermoscopy.
  • Check hepatitis C serology in all patients with lichen planus, especially with widespread or oral involvement.
  • Erosive oral and genital LP carries a small but real risk of SCC transformation — biopsy non-healing ulcers.
  • Frontal fibrosing alopecia is now considered a variant of lichen planopilaris and is rising sharply in incidence, particularly in postmenopausal women — early treatment may preserve hairline.

References

  • AAD/BAD — British Association of Dermatologists' Guidelines for the Management of Lichen Planus (Ioannides et al., Br J Dermatol 2020)
  • WHO 2005 — WHO Classification of Oral Potentially Malignant Disorders (van der Waal, Oral Oncol 2009)
  • AAD 2024 — Approach to Cicatricial Alopecias including Lichen Planopilaris (AAD updated work group statements)

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Related Dermatology diagnoses

Acne VulgarisRosaceaAtopic Dermatitis (Eczema)Allergic and Irritant Contact DermatitisSeborrheic DermatitisPsoriasisPityriasis RoseaTinea Infections (corporis, capitis, pedis, cruris, versicolor)Cutaneous CandidiasisScabiesPediculosisImpetigoHerpes Zoster (Shingles)Verrucae (Warts, HPV)

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