DR4.1 | Lichen Planus Diagnosis and Management — Summary & Reflection

KEY TAKEAWAYS

Lichen planus is a common T-cell-mediated lichenoid disease recognised by its classic clinical 'P' features — pruritic, purple (violaceous), polygonal, planar (flat-topped) papules — together with the diagnostic surface sign of Wickham striae, in a flexural distribution and with a positive Koebner phenomenon but no Auspitz sign. CD8+ cytotoxic lymphocytes attack basal keratinocytes at the dermoepidermal junction, producing Civatte bodies, a band-like infiltrate, saw-tooth rete ridges, and hypergranulosis; triggers include drugs (lichenoid drug eruption), hepatitis C, and dental amalgam. It involves skin, oral mucosa (reticular, erosive — with ~1% malignant risk, plaque), nails (pterygium unguis), and scalp (lichen planopilaris causing scarring alopecia). It is distinguished from psoriasis (silvery scale, Auspitz, extensor sites, parakeratosis) and from lichenoid drug eruption, lichen simplex, leukoplakia, and candidiasis. Management is by potent topical steroids for limited disease, topical tacrolimus for mucosal/facial disease, and — importantly, unlike psoriasis — a short course of systemic corticosteroids for extensive disease, with surveillance of oral erosive disease.

REFLECT

Think about how easily lichen planus and psoriasis could be confused by an untrained eye — both itch, both Koebnerise, both produce papular eruptions — and yet how completely different they are in appearance, behaviour, and safe treatment. Reflect on the patient in our hook who borrowed a neighbour's psoriasis cream for what was actually lichen planus: how would a careful reading of colour, surface, and distribution have set her on the right path sooner? Consider the responsibility that comes with diagnosing oral erosive lichen planus — the commitment to long-term surveillance for malignant change — and the importance of remembering that systemic steroids, dangerous in psoriasis, are a reasonable option here. How will you train yourself to hold the psoriasis–lichen-planus contrast clearly in mind so that you never treat one as if it were the other?