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DR4.1 | Lichen Planus Diagnosis and Management — SDL Guide (Part 2)

Differential Diagnosis of Lichen Planus

Differential Diagnosis of Lichen Planus

Because several conditions can mimic lichen planus on the skin and in the mouth, a structured differential — anchored on the contrast with psoriasis — is essential to avoid mismanagement. The most important cutaneous comparison is with psoriasis: psoriasis gives erythematous plaques with thick silvery scale, a positive Auspitz sign, and an extensor distribution, whereas lichen planus gives violaceous flat-topped papules with Wickham striae, no Auspitz sign, and a flexural distribution. A lichenoid drug eruption can be clinically indistinguishable, so a careful drug history is mandatory; it resolves on withdrawing the culprit. Lichen simplex chronicus shows thickened skin with exaggerated skin markings from chronic rubbing but lacks Wickham striae. In the mouth, oral lichen planus must be separated from oral candidiasis (the white plaque can be scraped off and KOH is positive), leukoplakia (a fixed white patch that cannot be wiped away and is itself premalignant), and lichen sclerosus.

Lichen Planus vs Psoriasis: Bedside Comparison

Investigations to resolve doubt:

• Skin biopsy — the gold standard, showing lichenoid histology.
• Direct immunofluorescence (DIF) — shows globular cytoid (colloid) bodies staining for IgM and C3 at the dermoepidermal junction.
• Hepatitis C serology — given the recognised association.
• Drug history review to exclude a lichenoid drug eruption.

Management of Lichen Planus

Management of Lichen Planus

Managing lichen planus is guided by the site and extent of disease, and it differs from psoriasis in an important way that students must grasp: systemic corticosteroids are a legitimate and effective treatment here, not a contraindicated one. For limited cutaneous disease, the first-line treatment is a potent topical corticosteroid such as clobetasol propionate, which controls itch and flattens lesions; antihistamines help the pruritus. For oral, genital, or facial lichen planus, topical tacrolimus (a calcineurin inhibitor) is preferred because it avoids the mucosal and skin atrophy that prolonged topical steroids cause; intralesional triamcinolone is useful for thick hypertrophic plaques. For extensive or severe acute disease, a short, tapering course of systemic corticosteroids (for example oral prednisolone) is appropriate and effective — a key contrast with psoriasis, where systemic steroids are avoided because of rebound flares. Lichen planus does not carry that rebound risk, so systemic steroids are a reasonable option for widespread or distressing disease.

Lichen Planus Management by Site

Further points of management:

• Second-line options include hydroxychloroquine, acitretin, and phototherapy (narrowband UVB) for resistant or widespread disease.
• Oral erosive lichen planus requires long-term surveillance because of its small (~1%) risk of malignant transformation.
• Scarring alopecia from lichen planopilaris is usually permanent; treatment aims to halt progression early rather than to regrow lost hair.
• Identify and stop any culprit drug, and treat associated hepatitis C where present.

Self-Assessment — Lichen Planus Recognition and Management

Consolidate your understanding by rehearsing the whole diagnostic and therapeutic reasoning for lichen planus, deliberately contrasting it with psoriasis at every step, because that contrast is both clinically important and a favourite of examiners. A competent student can recite the classic 'P' features and the significance of Wickham striae, explain the lichenoid mechanism and its drug and viral associations, recognise oral, nail, and scalp involvement and their implications, distinguish lichen planus from psoriasis and the other mimics, and devise a site-appropriate management plan including the permitted use of systemic steroids. Work through the prompts below by imagining real patients and explaining your reasoning aloud; the ability to teach the psoriasis–lichen-planus contrast clearly is a good test of having truly learned it.

Self-check prompts:

• Recite the classic clinical 'P' features of lichen planus and name the diagnostic surface sign.
• Which nail change is pathognomonic of lichen planus?
• How does the safe use of systemic corticosteroids differ between lichen planus and psoriasis, and why?
• What is the first-line treatment for symptomatic oral erosive lichen planus, and what long-term action does that diagnosis require?
• List three features that separate lichen planus from psoriasis at the bedside.