PassFinals
Dermatology

Lichen planus

Lichen planus is an inflammatory interface dermatosis causing pruritic violaceous papules with Wickham striae and potentially persistent disease of the mouth, genitals, scalp or nails.

In a nutshell

Lichen planus is an inflammatory lichenoid dermatosis. Think shiny flat-topped violaceous or darker papules with Wickham striae on flexor wrists or ankles, but examine the mouth, genital mucosa, scalp and nails. Potent topical corticosteroids treat symptomatic skin disease; oral or genital erosive disease needs specialist care, dental surveillance and safety-netting for malignant change.

Classic presentation

A middle-aged adult has intensely itchy flat-topped purple papules on the flexor wrists with fine white lines; a second patient has bilateral lacy white oral patches with painful erosions.

Key points

  • Classic cutaneous lesions are flat-topped, shiny, violaceous or darker papules with Wickham striae.
  • Koebnerisation and post-inflammatory hyperpigmentation are common clues.
  • Inspect the mouth, gums, genitalia, scalp and nails because scarring or permanent damage can occur.
  • Potent topical corticosteroids are commonly used for symptomatic skin disease; oral disease needs specialist-directed topical treatment.
  • Persistent erosive oral, genital, scalp or nail disease needs specialist follow-up.
  • Oral lichen planus has a small malignant-transformation risk: maintain dental/oral review and reduce tobacco and alcohol exposure.
  • Unexplained oral ulceration lasting more than 3 weeks, a lump or a suspicious red/red-white patch needs the appropriate oral-cancer referral pathway.

First-line investigation

Full skin and mucosal examination with specialist biopsy when the diagnosis is uncertain, erosive or atypical; review medicines and triggers selectively.

Management

Assess mucosal and appendage risk

  • Examine mouth, gums, genitalia, scalp and nails as appropriate; urgently refer suspicious oral lesions, severe erosive disease, dysphagia, rapid hair loss or destructive nail disease.1,3,6

Confirm the lichenoid pattern

  • Look for flat-topped papules, Wickham striae, Koebnerisation and typical distribution; arrange biopsy when the diagnosis is uncertain or mucosal disease is erosive or atypical.1,3

Treat symptomatic skin disease

  • Use prescribed potent or very potent topical corticosteroid for affected skin with emollient care; tailor treatment to site and severity and follow BNF advice.1,2,5

Treat oral and genital disease

  • Use specialist-directed topical steroid preparations, maintain oral hygiene, avoid foods that trigger soreness and arrange dental/oral-medicine or gynaecology/urology review for persistent erosive or scarring disease.3,4,1

Refer severe, refractory or destructive disease

  • Refer widespread, erosive, scarring, scalp, nail or treatment-resistant disease for phototherapy or specialist systemic treatment and monitoring.1,3,5

Surveil mucosa and safety-net

  • Maintain regular dental or oral-specialist review, reduce tobacco and alcohol exposure, review potential triggers and return urgently for new ulceration, bleeding, a lump, dysphagia or rapid progression.3,6,2

Exam traps

  • Lichen planus is not contagious and is not diagnosed by a positive infection test.
  • Do not treat persistent oral erosions empirically without considering biopsy and oral-cancer surveillance.
  • A lichenoid drug eruption can mimic lichen planus; do not stop essential medicines without prescriber input.
  • Scalp and nail disease can cause permanent damage, so early specialist review matters.
  • Avoid giving exact systemic immunosuppressant regimens outside specialist guidance; monitoring and indication vary.
  • The white lacy pattern supports oral lichen planus, but persistent ulceration, a lump or suspicious red/red-white change requires cancer referral.

Illustrations

Cutaneous lichen planus of the lower legsA clinical photograph showing multiple bilateral violaceous to darker papules and plaques of cutaneous lichen planus on the lower legs, with fine surface striae where visible.James Heilman, MD, Wikimedia Commons · CC-BY-SA-3.0
Oral lichen planusA sensitive clinical photograph of buccal mucosa showing a lacy white reticular network typical of oral lichen planus, with or without erosive change.Ian Furst, Wikimedia Commons · CC-BY-SA-4.0

Key sources

  1. British Association of Dermatologists: Lichen planus patient information leaflet (BAD consensus information on cutaneous, mucosal, scalp, nail and genital disease, diagnosis, topical and specialist treatment, and cancer risk; updated March 2024 and accessed 4 August 2026.)Updated 1 Mar 2024
  2. NHS: Lichen planus (Current NHS information on skin, mouth, genital, scalp and nail symptoms, treatment and self-care; accessed 4 August 2026.)
  3. British Association of Dermatologists and British Society for Oral Medicine: Oral lichen planus (UK oral-medicine consensus information on oral presentation, biopsy, topical treatment, dental follow-up, risk reduction and malignant change; updated March 2023 and accessed 4 August 2026.)Updated 1 Mar 2023
  4. University College London Hospitals NHS Foundation Trust: Lichen planus of the mouth (Current specialist NHS oral-medicine information on oral diagnosis, topical and systemic treatment, regular review and oral-cancer risk reduction; updated 28 May 2026 and accessed 4 August 2026.)Updated 28 May 2026
  5. British National Formulary (BNF) (BNF online prescribing information for topical corticosteroids, emollients, oral corticosteroids and immunomodulatory treatment; current product-specific details and monitoring must be checked at the point of care; accessed 4 August 2026.)
  6. NICE NG12: Suspected cancer: recognition and referral (Current NICE oral-cancer referral criteria for persistent oral ulceration, lumps and suspicious red or red-white patches; last updated 15 April 2026 and accessed 4 August 2026.)Updated 15 Apr 2026

This page is exam revision material, not medical advice, and must not be used for patient care. Always check drug doses against the BNF and current guidance. Full disclaimer.