A 48-year-old man from rural India presents with a 6-week history of intensely pruritic lesions on his wrists, lower legs, and dorsal hands. On examination, he has discrete, shiny, flat-topped purple papules arranged in a linear pattern on his forearms (Koebner phenomenon evident along a scratch mark). Oral examination reveals white reticular lines on the buccal mucosa without erosions. He has no systemic symptoms, normal liver function tests, and negative hepatitis serology. A skin biopsy shows a dense band-like lymphocytic infiltrate in the superficial dermis with a characteristic saw-tooth appearance of rete ridges and vacuolar degeneration of basal keratinocytes. What is the most appropriate first-line management for his cutaneous lesions?

Explanation

## Management of Cutaneous Lichen Planus ### Treatment Hierarchy | Severity | First-Line | Second-Line | Third-Line | |----------|-----------|------------|------------| | **Mild–moderate cutaneous** | Topical corticosteroids | Topical calcineurin inhibitors | Oral corticosteroids | | **Moderate–severe cutaneous** | Topical + systemic corticosteroids | Systemic retinoids | Cyclosporine, azathioprine | | **Erosive oral** | Topical corticosteroids/tacrolimus | Systemic corticosteroids | Retinoids, biologics | | **Generalized/severe** | Systemic corticosteroids ± retinoids | Cyclosporine, azathioprine | Biologic agents | ### Why Topical Corticosteroids Are First-Line Here **Key Point:** For mild-to-moderate cutaneous lichen planus WITHOUT significant oral erosions or systemic involvement, topical corticosteroids are the gold standard first-line therapy. **Clinical Pearl:** This patient has: - Localized cutaneous disease (wrists, lower legs, dorsal hands) - Non-erosive oral involvement (reticular lines only, no erosions) - No systemic symptoms or hepatic involvement - Normal investigations These features define **mild-to-moderate** disease, making topical therapy appropriate. ### Topical Corticosteroid Regimen 1. **Choice**: Potent corticosteroids (Class III–IV) such as: - Clobetasol propionate 0.05% (most potent) - Betamethasone dipropionate 0.05% - Fluocinonide 0.05% 2. **Application**: Twice daily to affected areas 3. **Duration**: 4–8 weeks, then taper 4. **Adjuncts**: - Emollients to prevent skin barrier damage - Avoid prolonged use on face/intertriginous areas (risk of atrophy) **High-Yield:** Topical corticosteroids achieve remission in 60–80% of patients with cutaneous lichen planus when used consistently. ### Response Monitoring - Assess at 4 weeks: lesions should flatten and pruritus should decrease - If inadequate response → escalate to systemic therapy - Maintenance: Intermittent topical corticosteroids to prevent relapse ### When to Escalate to Systemic Therapy ```mermaid flowchart TD A[Lichen Planus Diagnosed]:::outcome --> B{Disease Severity?}:::decision B -->|Mild-moderate cutaneous| C[Topical corticosteroids]:::action B -->|Moderate-severe cutaneous| D[Topical + systemic corticosteroids]:::action B -->|Erosive oral/generalized| E[Systemic corticosteroids ± retinoids]:::action C --> F{Response at 4 weeks?}:::decision F -->|Good| G[Continue, then taper]:::action F -->|Poor| H[Add systemic corticosteroids or retinoids]:::action D --> I[Oral prednisolone 0.5-1 mg/kg/day]:::action E --> J[Prednisolone + acitretin or cyclosporine]:::action ``` **Mnemonic:** **TOSS** — Topical first, Oral if severe, Systemic retinoids if resistant, Switch to biologics if refractory