What is Lichen Planus?
Lichen planus is a chronic, T cell-mediated inflammatory disease affecting the skin, oral mucosa, genital mucosa, scalp, and nails, classically presenting as violaceous, polygonal, flat-topped papules and plaques with characteristic fine white lines called Wickham striae. 1, 2
Clinical Presentation
The disease is traditionally described using the "six P's":
Distribution and Appearance
- The acute onset typically affects the flexor surfaces of the wrists, forearms, and legs with significant pruritus 1, 2
- Wickham striae—fine, lacy, reticular white lines covering the lesions—are a key diagnostic feature that distinguishes lichen planus from other papulosquamous conditions 1
- In chronic cases, lesions may become more hyperkeratotic and plaque-like 1
Mucosal Involvement
- Oral lichen planus is the most extensively studied phenotype and represents a common chronic inflammatory condition of the oral mucosa 4, 5
- Esophageal lichen planus is the most common dermatologic condition affecting the esophagus, occurring in isolation in approximately 33% of cases 4
- Endoscopic findings include narrowed esophageal caliber, pale edematous mucosa with peeling/sloughing upon contact, and thick white exudates 4
Pathophysiology
- Lichen planus is a T cell-mediated autoimmune disease with immune dysregulation playing a central role 4, 6
- Histologically, the disease shows a lichenoid inflammatory infiltrate with vacuolar degeneration of the basal layer of the epidermis and a band-like pattern of inflammatory T cells in the upper dermis 7, 6
Etiology and Associations
- Hepatitis C virus (HCV) infection is strongly associated with lichen planus, particularly oral lichen planus, in certain geographical regions 4
- The disease may be drug-induced, typically by anti-hypertensive medications 6
- Lichen planus can affect the nails in isolation, though this is rare 6
Diagnosis
- Classic cases may be diagnosed clinically, but a 4-mm punch biopsy is helpful for confirmation and required for atypical presentations 2
- Direct immunofluorescence (DIF) may help distinguish lichen planus from other conditions, particularly in mucosal disease 4
- Biopsy is essential to confirm diagnosis and rule out malignancy 8
Key Differential Diagnosis
Lichen planus must be distinguished from lichen sclerosus, which presents with:
- Porcelain-white papules and plaques, often with areas of ecchymosis 4, 1
- Predominant anogenital involvement that spares vaginal mucosa, whereas lichen planus can involve true mucosal surfaces 1
- Different histopathological features including hyperkeratosis, hydropic degeneration of basal cells, and homogenization of collagen 8
Treatment Approach
- High-potency topical corticosteroids (such as clobetasol) are first-line therapy for all forms of lichen planus, including cutaneous, genital, and mucosal erosive lesions 2
- Topical tacrolimus appears effective for vulvovaginal lichen planus 2
- Systemic corticosteroids should be considered for severe, widespread disease involving oral, cutaneous, or genital sites 2
- For severe disease unresponsive to topical treatment, referral to dermatology for systemic therapy with acitretin or oral immunosuppressants is warranted 2
- Emerging therapies include Janus kinase inhibitors and biologics (anti-IL-12/23, anti-IL17) as novel future treatment options 6
Clinical Course and Prognosis
- Cutaneous lichen planus may resolve spontaneously within one to two years, although recurrences are common 2
- Mucosal lichen planus tends to be more persistent and resistant to treatment than cutaneous disease 2, 7
- The disease does not typically cause scarring in cutaneous sites but can lead to scarring in mucosal areas and the scalp 4
- Despite often being self-limiting, the intractable pruritus and painful mucosal erosions result in significant morbidity and psychosocial burden 7, 6