Contents
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
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