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ukmla 2026

Lichen Planus

5 Ps: Pruritic, Purple, Polygonal, Planar Papules — Wickham's striae, flexor surfaces, Koebner positive. Oral erosive LP has SCC risk

Review date
reviewed 2026-04-05
Reading time
4 min read
Author
Dr Kola Tytler MBBS CertHE MBA MSt MRCGP
Dermatologyless-commonchronic
On this page
Condition details
Dermatology
less-common
4 min read
reviewed 2026-04-05
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About This Page

This is a clinician-written, evidence-based summary aligned to the 2026 MLA Content Map. It is intended for medical students and junior doctors preparing for the UKMLA. Always cross-reference with NICE guidance, local protocols, and clinical judgement.

Key points

  • 5 Ps: Pruritic, Purple, Polygonal, Planar (flat-topped) Papules/Plaques
  • Wickham's striae: fine white lacy lines on surface — pathognomonic
  • Koebner positive. Flexor surfaces (wrists, ankles) — opposite to psoriasis
  • Oral LP: white reticular pattern on buccal mucosa. Erosive form is premalignant (~1% SCC risk)
  • Self-limiting ~18 months for cutaneous. Screen for hepatitis C

Overview

Lichen planus is a T-cell mediated inflammatory condition affecting skin, oral mucosa, nails, and hair. Characteristic violaceous flat-topped papules with Wickham's striae. Cutaneous LP self-limiting in ~65% within 18 months. Erosive oral LP has ~1% malignant transformation risk. Associated with hepatitis C.

Epidemiology

~1% of population. Peak 30-60 years. Female preponderance. Drug triggers (lichenoid eruptions): gold, antimalarials, thiazides, NSAIDs, ACE inhibitors.

Clinical Features

Symptoms
Intensely pruritic violaceous flat-topped polygonal papules — 5 Ps
Flexor surfaces: wrists (most common), ankles, lower back
Oral: white reticular lacy pattern on buccal mucosa (often asymptomatic)
Erosive oral LP: painful erosions and ulceration
Nail: longitudinal ridging, pterygium
Signs
Violaceous flat-topped papules with Wickham's striae
Koebner phenomenon
Oral: bilateral white reticular pattern on buccal mucosa
Post-inflammatory hyperpigmentation as lesions resolve

Investigations

First-line
Clinical diagnosisWickham's striae on dermoscopy aids diagnosis
Skin biopsyBand-like lymphocytic infiltrate, saw-tooth rete ridges, civatte bodies
Second-line
Hepatitis C serologyScreen all patients with lichen planus
DIFShaggy fibrin deposition along basement membrane

Management

BAD Guidelines + NICE CKS
1
Cutaneous LP
  • Potent topical corticosteroid for symptomatic lesions
  • Reassurance: self-limiting ~65% within 18 months
  • Extensive: NB-UVB, oral retinoids, short course prednisolone
2
Oral LP
  • Reticular: often asymptomatic — monitor only
  • Erosive: potent topical steroid mouthwash or tacrolimus
  • Long-term follow-up: ~1% SCC transformation risk

Complications

  • Post-inflammatory hyperpigmentation
  • Oral SCC: ~1% transformation risk from erosive oral LP
  • Scarring alopecia: From lichen planopilaris
  • Vulvovaginal scarring/stenosis
UKMLA Exam Tips
  • 15 Ps: Pruritic, Purple, Polygonal, Planar, Papules
  • 2Wickham's striae = pathognomonic
  • 3FLEXOR surfaces — opposite to psoriasis (EXTENSOR)
  • 4Erosive oral LP: malignant transformation risk (SCC)
  • 5Screen for hepatitis C in all LP patients
  • 6Koebner: also in psoriasis, vitiligo, warts

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Verified Sources & References

BAD — Lichen Planus Guidelines
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