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

• 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

• 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

• 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

• Drug reaction – Lichenoid drug eruption. Commonly implicated drugs include:
  • Gold
  • Hydroxychloroquine
  • Captopril
  • Quinine
  • Thiazide diuretics
• Eczema – especially when distributed on flexor surfaces
• Psoriasis
• Candidiasis – when affecting the mouth or vagina
• Lichen sclerosis – when affecting the external genitals
• Pemphigus
• Sarcoidosis
• Basal cell carcinoma – when single lesions

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’s 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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