Lichen planus and interface dermatitis
- Lesion
Lichen planus causes itchy, flat, purple bumps and white lacy patches in the mouth. It is a T-cell attack on the base of the skin.
What it is
Lichen planus is a self-limited (on skin) or chronic (in mouth) inflammatory disease in which cytotoxic T cells attack basal keratinocytes. The clinical «six Ps» (pruritic, purple, polygonal, planar papules and plaques) match a classic band-like lymphocytic infiltrate at the dermoepidermal junction. It belongs to the interface dermatitis family together with lupus erythematosus and erythema multiforme, each with a distinctive twist.
Step by step
- An unknown antigen (perhaps altered self or viral) is presented by basal keratinocytes or Langerhans cells.
- CD8 cytotoxic T cells accumulate along the dermoepidermal junction.
- They kill basal keratinocytes by apoptosis (Civatte bodies) and vacuolise the basal layer.
- The epidermis responds with hypergranulosis and hyperkeratosis; rete ridges take a sawtooth shape.
- Melanin falls into the dermis and is taken up by macrophages: post-inflammatory hyperpigmentation.
Interface dermatitides compared
| Disease | Infiltrate | Distinctive features |
|---|---|---|
| Lichen planus | Dense band-like at the junction | Sawtooth rete, hypergranulosis, Civatte bodies |
| Discoid lupus | Superficial and deep, around vessels and adnexa | Follicular plugging, dermal mucin, thick basement membrane, scarring |
| Erythema multiforme | Sparse, superficial | Scattered apoptotic keratinocytes, acute |
| Lichenoid drug eruption | Band-like with eosinophils | Parakeratosis, deeper infiltrate |
| Graft-versus-host disease | Sparse | Satellite cell necrosis after transplant |
Clinical notes
- Skin lesions often resolve within one to two years, leaving pigmentation; oral disease persists.
- Check hepatitis C status in oral or extensive lichen planus.
Test yourself
Think of the answer, then tap the question to see it.
What are Civatte bodies?
Apoptotic basal keratinocytes, seen as round eosinophilic bodies at the dermoepidermal junction in lichen planus.
Which infection is associated with lichen planus?
Hepatitis C virus infection.
How does discoid lupus differ histologically from lichen planus?
Lupus has a superficial and deep perivascular and periadnexal infiltrate, follicular plugging, dermal mucin and a thickened basement membrane.
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Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Skin Conditions (MedlinePlus, US National Library of Medicine, 2025).
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Representative model, for educational purposes only.