Lichen Planus

Question 1

Description of Lichen Planus

Answer 1

• Common chronic inflammatory disease of skin and mucous membranes (1-2% of population)
• Middle age or older (40+)
• 1/3 have skin lesions only
• 1/3 have oral lesions only
• 1/3 have both oral and skin lesions

Question 2

Aetiology of lichen planus

Answer 2

unknown

Question 3

Pathogenesis of lichen planus

Answer 3

• Immunologically mediated process
• Cytotoxic T cells and few T helper cells migrate into basal laters of epidermis and mucosal epithelium
• They destroy basal cells by direct cytotoxicity using perforin and enzymes released into the cell or through the secretion of TNF-alpha or cytokines
• Basal cells die via apoptosis
• Epithelium now has fewer proliferating cells to renew itself, so becomes thinner. Attachment of epithelium becomes weaker and can separate
• Damage to epithelium causes recruitment of lymphocytes to form band of infiltrate below epithelium
• Process in state of balance
  1. when basal cell destruction dominates, epithelium becomes atrophic or ulcerates - symptoms increase
  2. when immunological reaction decreases, remaining basal cells proliferate and recover, epithelium thickens and more keratinised - symptoms may vanish
  3. cause of cyclical cycle is unclear

Question 4

Clinical presentation of skin lesions? How do you manage?

Answer 4

• Purplish papules 2-3mm across - usually itchy
• Sites: flexor surface of forearms, wrist, shins and back
• Easy to treat with steroids
• Suffer for a few years

Question 5

Clinical presentation of oral lesions? How do you manage?

Answer 5

• Lesions are usually bilateral and often symmetrical
• Lesions can comprise of: striae, atrophic area, ulcers, plaques
• Sites: buccal mucosa (most common), tongue (lateral margins or dorsum), gingiva (affected by desquamative gingivitis: full width of attached gingiva)

Question 6

If found in what intraoral areas, should the diagnosis of lichen planus never be accepted? and why?

Answer 6

• When affected ventral tongue, floor of mouth or palate should not be accepted unless typical changes elsewhere
• Involvement raises suspicion of malignant dysplastic process or drug reaction

Question 7

How can lichen planus be physically classified? Why is there a range of appearances?

Answer 7

• depending on balance of destruction and resolution, there can be a range of appearances

1. Reticular - meshwork pattern of striae that criss cross
2. Papular
3. Plaque-type - solid areas of keratinisation
4. Atrophic (erythematous): red areas caused by inflamed submucosa showing though thin epithelium
5. Erosive
6. Bullous: results from separation of epithelium forming blisters that break down into ulcers
7. Ulcerative: basal cell destruction to extent that epithelium cannot renew itself and ulcers develop. Raised yellow layers of fibrin - usually surrounded by atrophic areas with striae

• Can be simply classified as ulcerative/erosive or non-ulcerative/non-erosive

Question 8

Management of oral lesions

Answer 8

• Difficult to treat

- Oral lesions for life, although severity may reduce with age

Question 9

Histopathology of lichen planus

Answer 9

• Dense band-like lymphocytic infiltrate under epithelium
• Saw tooth rete pegs (looks like a saw) (common in skin)
• Hyperkeratosis and acanthosis (increase in thickness of prickle cell layer) - although in atrophic forms the epithelium is thinner
• Apoptotic degeneration of basal cells
• Widening of BM zone
• Sometimes melanin dropout/post inflammatory hyperpigmentation

Question 10

Diagnosis of LP

Answer 10

• Usually can be made on history, appearance and distribution of lesions
• Check for drugs that can cause lichenoid reaction
• Ideally confirmed by biopsy - required for all white lesions to exclude dysplasia
• biopsy avoided if typical LP and follow up appt is given
• Biopsy given if plaque-type or unusual lesion as it is difficult to distinguish from leukoplakia

Question 11

management of LP

Answer 11

• No curative tx - aims to relieve pain and promote healing (good symptomatic response to corticosteroids)
  1. Reassurance and education
  2. Optimise oral hygiene
• sensitivity prevents tooth brushing but plaque accumulation can worsen inflammation
• CHX mouthwash and non-astringent toothpaste
  3. Analgesic for pain relief
• Benzydamine hydrocholoride, 5% lignocaine gel
  4. Topical steroids
• adhesive tablets (mild), steroid gel in vacuum formed tray (medium potency), mouthwash preparation (generalised)
  5. Intralesional steroids
  6. systemic steroids
• Corticosteroids, cyclosporine, azathioprine, hydroxychloroquine
  7. disease modifying agents
• e.g. anti-TNF therapy

Question 12

What could the the possible reason for LP worsening?
Why does this happen?
what is the tx?

Answer 12

• When inflammation worsens or symptoms become more severe consider the possibility of superimposition of candida
• Increased keratinisation and steroid tx = increased candida
• Tx: anti fungal

Question 13

When should lesions be followed up, and why?

Answer 13

• Follow up associated with reddening, and if unusual site, appearance or severity
• Squamous carcinoma may develop in lesions rarely (0.03-1.8%) particularly oral lichen planus can turn into oral squamous carcinoma

Question 14

What are lichenoid reactions?

Answer 14

• Lichen planus-like lesions (erythema, vesicle formation/ulceration) caused by a trigger - usually a drug
• Cannot be confidently distinguished from lichen planus
• Lichenoid reactions are often more severe
  1. onset closely associated with potential cause
  2. Unilateral/asymmetrical/unusual distribution
  3. Unusal severity
  4. widespread skin lesions
  5. localised lesion in contact with potential cause

Question 15

Mechanism of lichenoid reactions

Answer 15

• Type IV hypersensitivity reaction (delayed)
• Contact allergy
• Cell mediated immune reaction
• Burning/itching sensation

Question 16

What is the histopathology of lichenoid reactions

Answer 16

• Subepithelial infiltrate
• More eosinophils and plasma cells
• More diffuse than LP
• Extends more deeply
• Otherwise no specific test

Question 17

Which drugs can cause lichenoid reactions

Answer 17

Colloidal gold
beta blockers
oral hypoglycaemics
allopurinol
NSAIDs
antimalarials
methyldopa
penicillamine
some tricyclic antidepressants
thiazide diuretics
captopril

Question 18

How long can drug lichenoid reactions persist after administration

Answer 18

months to years

Question 19

Cause of drug lichenoid reactions?

Answer 19

• unclear cause
• Either: drug binds to epithelial cells and elicits and antigen-specific response
• Or: drug is metabolised differently in the epithelium of susceptible pts triggering immune response

Question 20

Diagnosis of lichenoid drug reactions

Answer 20

• Resolution on removal of stimulus, followed by relapse on replacement
• Biopsy: histologically very subtle difference between lichenoid and LP but needed to exclude other conditions

Question 21

Treatment of lichenoid drug reactions

Answer 21

• Withdrawal of drugs if possible
• Changing to another drug may be helpful but same class of drugs may cause same reaction
• reaction does not disappear immediately after withdrawal e.g. with amalgam takes 2-3 years

Question 22

Topical restoration lichenoid reactions clinical presentations

Answer 22

• usually amalgam but can be due to polymeric materials
• Clinical appearance close to LP but localised to mucosa close to restoration
• Common sites: posterior buccal mucosa, posterior ventral tongue
• Lesions composite only striae or plaque - more severe have ulceration/atrophy centrally
• amalgams that have corroded more likely to cause reason
• healing follows removal of restorations confirms lichenoid reaction

Question 23

Clinical presentation of cinnamon stomatitis and plasma cell gingivitis

Answer 23

• cinnamon (toothpaste/gum/food) can cause topical lichenoid reaction
• histological features similar to LP
• Clinically more likely to be patchy irregular keratosis without significant erythema
• Gingival and adjacent mucosa may be bright red
• Diagnosis based on resolution after withdrawal of allergen