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.
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, 5,500+ board-style questions, flashcards, and an AI tutor. Your 7-day free trial includes everything, and there's no credit card required.
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 |
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. 5,500+ board-style questions with an AI tutor that explains every answer — free to start, no card required.
Start studying free → Browse all 514 diagnosesEducational 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 or PAEA. PANCE® and PANRE® are registered trademarks of the National Commission on Certification of Physician Assistants; End of Rotation™ is a program of the Physician Assistant Education Association.