Lichen planus

Lichen planus is a chronic inflammatory disease of unknown origin that is characterized by different types of lesions involving the skin and mucosa in middle-aged individuals. 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, a possible complication of genital 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.

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

• Altered immune response with T cell activation ^[3]
• Associated with hepatitis C infections

Lichen planus may affect the skin, mucosa, scalp, genitalia, and nails, and presents with varying symptoms depending on the subtype of the disease. The condition is chronic and usually manifests with several relapses. ^[4]

Cutaneous lichen planus ^[1]

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 ^[5]
  • 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 7 P's of lichen Planus are Pruritic, Polygonal, Planar (flat-topped), Purple Papules, and Plaques.

Lichen planus can manifest with several subtypes, including: ^[5]

• 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

• Hyperkeratosis
• Wedge-shaped hypergranulosis ^[1]
• Irregular acanthosis (saw-tooth appearance) ^[1]
• Band-like lymphocytic infiltrate at the dermal-epidermal junction ^[7]

Lichen sclerosus (et atrophicus) ^[8][7]

• Definition: Lichen sclerosus is a chronic inflammatory disease with characteristic white, atrophic plaques.
• Epidemiology
  • Rare disease
  • More common in women (postmenopausal)
• Etiology: unknown (genetic, immunological and hormonal factors likely play a role)
• Clinical features ^[6]
  • Lesions
    • Early disease
      • Papules and plaques that are white, polygonal, well-demarcated, and potentially surrounded by a red inflammatory halo
      • Severe pruritus, possibly pain/soreness
    • Advanced disease: lichenification, skin thinning/fragility, and erosive scarring
  • Distribution pattern
    • Anogenital
      • Women: vulvar and perianal area; with “figure eight” appearance (can cause dyspareunia) ^[9]
      • Men: glans penis (can cause phimosis)
      • Both: anus (can cause anal fissure and/or painful defecation)
    • Extragenital: most commonly on back, shoulders, neck, wrists, thighs and under the breast ^[10]
• Diagnosis ^[11]
  • Suspected based on clinical presentation
  • Punch biopsy
    • Confirms diagnosis and rules out squamous cell carcinoma
    • Shows epidermal atrophy with hyperkeratosis and/or dermal fibrosis and sclerosis ^[12]
• Treatment ^[11]
  • High potency topical steroids (clobetasol, sometimes betamethasone) OR calcineurin inhibitors (tacrolimus)
  • If necessary, surgical excision
• Complications
  • Slightly increased risk of cancer (vulvar carcinoma) ^[13]
  • Destructive scarring

Others

• Drug-induced lichen planus (lichenoid drug eruption): a dermatologic condition that is triggered by certain drugs (e.g., beta blockers, ACE inhibitors, penicillamines) and manifests with lesions that closely resemble lichen planus but are not histologically identical. ^[14]
• Chronic graft-versus-host disease
• Psoriasis (guttate psoriasis and plaque psoriasis)

The differential diagnoses listed here are not exhaustive.