Dermatology · PANCE / PANRE

Lichen Planus

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.

🔒 Free preview limit reached

Keep reading — start your free trial

You've read your 2 free diagnosis previews. Create your free account to unlock the full Lichen Planus outline — plus all 514 diagnoses, 3,500+ board-style questions, flashcards, and an AI tutor. Your 7-day free trial includes everything, and there's no credit card required.

Start your 7-day free trial → Sign in

Free to start · No credit card · Cancel anytime

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

Site	Typical Lesion	First-Line Therapy
Cutaneous (wrists, ankles, shins)	Pruritic violaceous polygonal papules with Wickham striae	High-potency topical steroid (clobetasol)
Oral (reticular)	Asymptomatic white reticular striae on buccal mucosa	Observation; oral hygiene
Oral (erosive)	Painful ulcers, gingivitis	Topical clobetasol gel, dexamethasone rinse, topical tacrolimus
Genital	Erosive vulvovaginal-gingival syndrome; penile papules	Topical clobetasol/tacrolimus; vaginal dilators
Scalp (LPP, FFA)	Scarring alopecia, perifollicular erythema	Topical/IL steroid + hydroxychloroquine ± 5ARI
Nails	Longitudinal grooves, pterygium	IL 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)

Practice Dermatology questions on FirstPassPA

Turn this outline into retention. 3,500+ board-style questions with an AI tutor that explains every answer — free to start, no card required.

Start studying free → Browse all 514 diagnoses

Educational use only. This outline is a study aid for PA students and is not medical advice or a substitute for clinical judgment. FirstPassPA is an independent study tool and is not affiliated with, endorsed by, or sponsored by NCCPA. PANCE® and PANRE® are registered trademarks of the National Commission on Certification of Physician Assistants.