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
• Associated with hepatitis C infections

References:^[2][3]

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.

Cutaneous lichen planus

• Primary lesion
  • Purple papules, well-demarcated
  • Planar (flat-topped)
  • Polygonal, irregular borders
  • Pruritic, often severe
  • Wickham's striae: pattern of white lines on the lesion's surface
• Distribution pattern
  • Affects the extremities, especially the ankles and flexor wrists; trunk
  • Lesions arranged in linear or circular groups; may coalesce into larger plaques
  • Bilateral, symmetrical distribution
• Manifests with the Koebner phenomenon
• May occur simultaneously with other subtypes

Mucosal lichen planus

• Oral lichen planus
  • Asymptomatic (lacelike Wickham's striae are the only finding) or
  • 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 vulva and vagina
• Pruritus, burning sensation, dyspareunia

The 5 P's of lichen planus: Pruritic, Polygonal, Planar (flat-topped), Purple papules, and Plaques!

References:^{[4][1][2][3][5][6]}

• Histology
  • Hyperkeratosis
  • Wedge-shaped hypergranulosis
  • Irregular acanthosis (saw-tooth appearance)
  • Band-like lymphocytic infiltrate at the dermal-epidermal junction

References:^[1][2]

Lichen sclerosus (et atrophicus)

• Definition: Lichen sclerosus is a chronic inflammatory disease with characteristic white, atrophic plaques.
• Etiology: unknown; but genetic, immunological and hormonal factors likely play a role
• Epidemiology: : rare disease; more common in women (postmenopausal)
• Localization
  • Anogenital: vulvar and perianal area in women; → classic “figure eight” appearance; glans penis in males
  • Extragenital: most commonly on back, shoulders, neck, wrists, thighs and under the breast
• Lesions
  • Initially: papules and plaques that are white, polygonal, well-demarcated, and may be surrounded by an inflammatory halo
  • Later: lichenification and erosive scarring
• Clinical presentation
  • Severe pruritus, pain/soreness, anal fissure, painful defecation
  • Dyspareunia in women, and phimosis in men
• Diagnosis
  • Suspected based on clinical presentation
  • Punch biopsy: confirms diagnosis and rules out squamous cell carcinoma
• Complications
  • Increased risk of cancer (vulvar carcinoma; squamous cell carcinoma)
  • Destructive scarring
• Treatment
  • High potency topical steroids (clobetasol, sometimes betamethasone) or calcineurin inhibitors (tacrolimus)
  • If necessary, surgical excision

Others

• Drug-induced lichen planus (lichenoid drug eruption)
• Chronic GvHD (graft-versus-host disease)
• Psoriasis (guttate psoriasis and plaque psoriasis)

References:^{[7][8][9][2][3][10][11][12][13][14]}

The differential diagnoses listed here are not exhaustive.