Lichen planus

Lichen planus is a chronic inflammatory disease of unknown origin, which most commonly affects individuals between 30–60 years of age and is characterized by different types of lesions involving the skin and mucosa. The most common lesions are purple papules with well-demarcated, irregular borders, which typically occur on the wrists, lower extremities, and genitoanal region. The surfaces of the lesions often exhibit a pattern of white lines known as Wickham's striae. The disease is diagnosed clinically, but may be confirmed through dermoscopy and punch biopsies. Biopsy also helps detect squamous cell carcinoma, the risk of which is increased in lichen planus. Treatment primarily consists of high-dose topical steroids but may also include oral steroids and phototherapy in cases of extensive or steroid-refractory disease. Lichen planus is generally a chronic-recurrent condition, except for the cutaneous form, which is usually self-limiting.

• Prevalence: rare disease (occurs in < 1% of the population) ^[1][2]
• Age of onset: 30–60 years ^[3][4]
• Sex ^[1]
  • Cutaneous lichen planus: ♀=♂
  • Oral lichen planus is more common in women

Epidemiological data refers to the US, unless otherwise specified.

Although the exact etiology of lichen planus is unknown, possible etiologic factors include:

• Altered immune response with T cell activation ^[5][6]
• Associated with hepatitis C infections ^[7]

Lichen planus can affect the skin, mucosa, scalp, genitalia, and nails, and manifests with varying symptoms depending on the subtype of the disease.

Cutaneous lichen planus ^[2]

May occur simultaneously with other subtypes

• Lesions
  • Purple, well-demarcated papules or plaques
  • Planar (flat-topped)
  • Polygonal, irregular borders
  • Pruritic, often severe
  • Wickham striae: white, reticular lines on the surface of mucosal lesions
• Distribution pattern
  • Affects the extremities, especially the ankles and flexor wrists, as well as the trunk
  • Lesions arranged in linear or circular groups that may coalesce into larger plaques
  • Bilateral, symmetrical distribution ^[8]
  • Lesions often develop in previously traumatized skin (Koebner phenomenon)

Mucosal lichen planus

• Oral lichen planus
  • Asymptomatic (lace-like Wickham striae are the only finding)
  • Painful, atrophic and erosive lesions
• Esophageal lichen planus
  • Submucosal papules, mucosal plaques, and erosions
  • Possible dysphagia and painful swallowing

Genital lichen planus

• Papules on glans penis or vulvovaginal
• Pruritus, burning sensation, dyspareunia

The 6 P's of lichen Planus are: Pruritic, Polygonal, Planar (flat-topped), Purple Papules, and Plaques.

Lichen planus can manifest with several subtypes, including: ^[8]

• Hypertrophic lichen planus (lichen planus verrucosus)
  • Verrucous plaques and nodules that are scaly
  • Predominantly affect the shins
• Lichen planopilaris
  • Mainly affects the scalp of postmenopausal women and presents with pruritus and hair loss
  • Frontal fibrosing alopecia (a variant of lichen planopilaris)
    • Affects the scalp with scarring alopecia
    • Histology: hair follicles are surrounded by a bandlike lymphocytic infiltrate
    • Direct immunofluorescence shows subepidermal colloid bodies

Lichen planus is clinically diagnosed based on the presence of typical skin lesions. Additional testing is performed to confirm the diagnosis and rule out other diseases.

• Punch biopsy ^[9]
  • Shows typical histology (see “Pathology” below)
  • Exclusion of vulvar carcinoma
• Dermoscopy: detection of Wickham striae
• Endoscopy: detection of esophageal involvement (erosions, plaques, inflamed mucosa)

• Hyperkeratosis
• Wedge-shaped hypergranulosis ^[2]
• Irregular acanthosis (saw-tooth appearance) ^[2]
• Band-like lymphocytic infiltrate at the dermal-epidermal junction ^[10]

• Lichen sclerosus
• Drug-induced lichen planus (lichenoid drug eruption)
  • A dermatologic condition that is triggered by certain drugs (e.g., beta blockers, ACE inhibitors, penicillamines, thiazide diuretics, hydroxychloroquine)
  • Manifests with diffuse lesions that closely resemble lichen planus but are not histologically identical. ^[11]
  • Management includes discontinuation of the suspected medication and topical glucocorticoids.
• Chronic graft-versus-host disease
• Psoriasis (guttate psoriasis and plaque psoriasis)

The differential diagnoses listed here are not exhaustive.

• First-line therapy
  • High-potency topical corticosteroids (e.g., betamethasone)
  • Intralesional application in hypertrophic areas
• Second-line therapy
  • Oral corticosteroids (e.g., prednisone)
  • Phototherapy (UVB and PUVA)
  • Oral retinoids (e.g., acitretin)
• Adjunctive therapy: oral antihistamines (e.g., hydroxyzine) to manage pruritus ^[10]

Any localization of erosive lichen planus can cause scarring, which may lead to functional limitations.

• Cutaneous lichen planus
  • Usually self-limiting (typically resolves within 1 year) ^[1]
  • Can cause lasting hypopigmentation and/or hyperpigmentation
• Oral lichen planus
  • Chronic condition
  • Potential precursor of squamous cell carcinoma
• Genital lichen planus: may lead to scarring and/or synechiae formation