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Introduction

Lichen planus (LP) is a chronic, inflammatory, puritic skin disorder, typically found on the limbs (especially flexor surfaces), mucous membranes (often in the mouth) and genitals – including inside the vagina.

Some divide lichen planus into various types – most commonly discerned by their location.

The cause is not well understood, but it likely a T-cell mediated autoimmune disorder.

Epidemiology

  • It typically affects adults over the age of 40
  • 1-4% worldwide prevalence
  • 50% of patients have oral lichen planus
  • 10% have lichen planus affecting the nails
  • More common in women M:F 1:1.5

Aetiology

  • Genetic predisposition
  • Physical and psychological stress
  • Skin trauma – often occurs after surgery, or at sites of herpes zoster infection
  • Systemic viral infection – e.g. hepatitis B or C – can also trigger LP
  • Contact dermatitis may precipitate LP

Pathology

  • T-cell mediated autoimmune disorder
  • T-cells attack an as-yet unidentified protein in the skin and nails

Presentation

Lichen planus on the shins

Lichen planus on the shins (not always a typical location, but lesions here are of typical appearance). This file is taken from wikimedia commons and is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.

Classical lichen planus

Classical lichen planus. Image from Dermnet. Used in accordance with Creative Commons Attribution-NonCommercial-NoDerivs 3.0 (New Zealand) license.

  • Typically an acute presentation
    • Often affects flexor surfaces on first presentation – the front of the elbows, inside of wrists and back of the knees
    • Itchy
    • Not typically painful, but can be
    • May also affect genitals
    • Mucuous membranes also common affected – inside of mouth, and to a lesser extent, vagina. Rarely – in the larynx or oesophagus
  • Distinct, often round, purpuric, raised lesions
  • Occasionally lesions blister
  • As the initial lesions heal, they often leave small flat brown discoloured circles
  • On mucous surfaces:
    • White, slightly raised lesions
    • Can appear like small ulcers, or like white streaks
    • Typically on tongue or inside of cheeks
    • Can be asymptomatic, but in some patients are very painful
    • Difficult to treat
  • Nails
    • Affected in about 10% of patients
    • Longitudinal lines
    • Severe cases may involve destruction of the nail bed
Lichen planus in fingernails

Lichen planus in fingernails. This file is taken from wikimedia commons and is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.

  • Scalp
    • Usually spared
    • If it is affected, can cause severe scarring and alopecia

Some subtypes of LP include:

  • Hypertrophic LP –¬†thick, raised lesions, typically leave hyper pigmentation as they resolve. Often very itchy
Hypertrophic lichen planus

Hypertrophic lichen planus. Image from Dermnet. Used in accordance with Creative Commons Attribution-NonCommercial-NoDerivs 3.0 (New Zealand) license.

  • Erosive / ulcerative –¬†often on mucosal surfaces. Often painful

Diagnosis

Diagnosis is usually clinical, but biopsy may be taken if there is uncertainty.

Histology of a skin biopsy has several characteristic features:

  • Saw-tooth pattern of epidermal hyperplasia
  • T-cell infiltration of dermis
  • Reduced melanocytes
  • Direct immunofluorescence shows globular deposits of Ig (usually IgM, sometimes IgG and IgA)

Differential diagnosis

Management

  • Many cases resolve spontaneously within a year
    • Itch tends to slowly decline with time, even if LP does not resolve
    • Mucous membrane disease tends to be more resistant to treatment
  • Topical steroids
    • Mainstay of treatment for particularly itchy or persistent lesions
    • Moderately potent steroids are typically used first
    • Stronger potency may be required – especially for lesions on the shins
    • Are also considered first line for mucous membrane lichen planus
  • Other treatments
    • Typically reserved for specialist use in particularly troublesome cases
    • Azathioprine, mycophenolate, retinoids and hydroxychloroquine may be used

Any scarring that occurs is permanent – including on the scalp – where it causes permanent baldness. This is usually rare.

Complications

  • Hyperpgimentation from previous lesions – especially hypertrophic lesions
  • 1% lifetime risk of oral squamous cell carcinoma. Higher risk if:
    • Smoker
    • Alcohol dependency
    • Hepatitis C infection
  • Rarely, carcinoma of the vulva is associated with LP

Flashcard

References

  • Murtagh‚Äôs General Practice. 6th Ed. (2015) John Murtagh, Jill Rosenblatt
  • Oxford Handbook of General Practice. 3rd Ed. (2010) Simon, C., Everitt, H., van Drop, F.
  • Beers, MH., Porter RS., Jones, TV., Kaplan JL., Berkwits, M. The Merck Manual of Diagnosis and Therapy
  • Lichen planus - dermnetnz
  • Lichen Planus - patient.info

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