Lichen planus

Question 1

What is lichen planus?

Answer 1

• chronic, inflammatory, pruritic skin disorder
• limbs, esp flexor surfaces
• mucous membranes
• genitals including inside vagina
• 6Ps: planar, polygonal, papules <5mm, plaques >5mm, purple, pruritic
• can be types according to location
• cause not well understood
• may be a T-cell mediated autoimmune disorder

Question 2

Epidemiology of lichen planus?

Answer 2

• affects adults over 40
• 1-4% prevalence world wide
• 50% have oral lichen planus
• 10% affects nails
• 1M : F1.5

Question 3

Aetiology and pathology of lichen planus?

Answer 3

Pathology:

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

Aetiology:

• genetic predisposition
• physical and psychological stress
• skin trauma; occurs at surgery sites or herpes zoster sites
• systemic viral can trigger LP eg hep B or C
• contact dermatitis can precipitate LP

Question 4

Presentation of lichen planus?

Answer 4

Typically an acute presentation:

• flexors (elbows, knees)
• ITCHY
• not usually painful
• may affect genitals
• inside mouth and sometimes vagina (wickhams striae)
• 6Ps: planar, polygonal, papules <5mm, plaques >5mm, purple, pruritic
• distinct, purpuric, raised lesions
• ocassionaly lesions blister
• after healing they leave small flat brown discoloured circles

Mucous surfaces:

• white, slightly raised lesions (Wickhams striae and lace)
• appear like small ulcers or white streaks
• tongue or inside cheeks
• can be asymptomatic or very painful

Nails:

• affects 10%
• longitudinal lines

Scalp

• usually spared
• if affected can cause severe scarring and alopecia

Subtypes:

• hypertrophic LP, thick, raised lesions, leave hyperpigmentation when they resolve
• erosive / ulcerative, often painful and on mucosal surfaces

Question 5

Diagnosis of lichen planus is usually clinical but what might be seen on skin biopsy?

Answer 5

• saw tooth pattern of epidermal hyperplasia
• T-cell infiltration of dermis
• reduced melanocytes
• direct immunofluorescence show globular deposits of Ig (usually IgM, sometimes IgG and IgA)

Question 6

Differential diagnosis when thinking lichen planus?

Answer 6

Consider:

• drug reaction; lichenoid drug reaction: gold, hydroxychloroquine, captopril, quinine, thiazide diuretics
• eczema
• psoriasis
• candidiasis
• lichen sclerosis (for external genitals)
• pemphigus
• sarcoidosis
• basal cell carcinoma when single lesions

Question 7

Management of lichen planus?

Answer 7

Topical steroids

Other: azathioprine, mycophenylate, retinoids, hydroxychloroquine

Oral lesions are harder to treat.
Any scarring is permanent.

Question 8

Complication of lichen planus?

Answer 8

• hyperpigmentation from previous lesion
• 1% lifetime risk of oral squamous cell carcinoma (higher is smoker, alcohol, hep C)
• rarely carcinoma of vulva is associated