Lichen planus

Synonyms: Knötchenflechte

By Dr. Pascal Bafteh · last updated 09/2026

Definition & Epidemiology

• Non-contagious acute, subacute to chronic, markedly pruritic and mostly self-limiting inflammatory disease of the skin and/or mucous membranes of unknown etiology.

• Affected: Adults in their 3rd–6th decade of life; women more frequently (esp. oral LP).

Pathogenesis & Triggers

• Triggers: Genetic predisposition, viral infections (HCV, HHV7&8), medications (NSAIDs, antimalarials, beta-blockers), stress, contact allergens (Metals/alloys such as gold, amalgam), pre-existing conditions (DM, lupus, collagenoses, AA, vitiligo), tumors (HCC, SCC, head and neck tumors).

• Pathomechanism: Basal keratinocytes present antigens via Langerhans cells via MHC-I to CD8+ T-cells → activation/proliferation of cytotoxic T-cells → release of IFN-γ, TNF-α, IL-1 → recruitment of macrophages/dendritic cells → apoptosis of keratinocytes by granzymes/perforins via FasL.

• Histopathology: Lymphocytic infiltrate, Civatte bodies, hypergranulosis, basal cell degeneration, acanthosis, hyperkeratosis, melanin incontinence.

Clinical Features

• Classic Morphology (6 P's): Flat, polygonal, pruritic, violaceous-reddish, shiny papules/plaques with fine white lines (Wickham's striae) on the surface.

• Predilection Sites: flexor aspects of wrists, lower legs, lower back.

• Mucosal Involvement: White reticular striae or erosions in the mouth (oral LP) and on the genitals; esophageal involvement possible.

Hair & Nails: Loss of the immune privilege of the stem cell niche → scarring alopecia (→ lichen planopilaris, LPP); Nail findings: longitudinal ridging, onycholysis, nail dystrophy, shiny nails.

Differential diagnoses

• Lichen planus
• Atopic dermatitis (atopic eczema)
• Psoriasis vulgaris (plaque psoriasis)
• Lichen striatus
• Granuloma annulare
• Dyshidrotic hand eczema (pompholyx)
• Secondary syphilis (lues II)
• Lichen planopilaris

Sources (selection)

1. Manchanda et al. 2023
2. Solimani et al. 2021
3. Schilling et al. 2018
4. Wechsuruk et al. 2021

More inflammatory skin diseases

• Cheilitis granulomatosa (Miescher)
• Erythema annulare centrifugum (EAC)
• Erythema nodosum
• Graft-versus-host disease (GvHD)
• Granuloma annulare
• Cutaneous sarcoidosis
• Lichen sclerosus
• Lichenoid drug eruption

Note: This page is intended for medical education and does not replace diagnosis or treatment decisions in individual cases. Treatment and follow-up content is available in the app.