LICHEN PLANUS

DERMATOLOGY LECTURE NOTES

DEBABRATA BANDYOPADHYAY
PROFESSOR & HEAD, DEPT. OF DERMATOLOGY,
R. G. KAR MEDICAL COLLEGE, CALCUTTA, INDIA

Lichen planus (pronounced 'ly-kin plan-us') is a common inflammatory disease of the skin presenting with characteristic violaceous, polygonal, pruritic papules. The disease may also affect the mucosa, hairs and  nails. Lichen planus (LP) occurs worldwide with no racial predilection. Although the aetiology is unknown, immunopathological mechanisms are implicated in the pathogenesis of the dermatosis.
 

ETIOLOGY & PATHOGENESIS

• The cause of LP is not known but immunologic mechanisms triggered by poorly defined antigenic stimulations plays a pivotal role in the pathogenesis of the disease. Cell-mediated immune response is believed to play the major role in the pathology of the disease. Presence of activated antigen presenting cells (Langerhans' cells, dendritic macrophages) in the lesional skin could be demonstrated in the early stage of the disease. CD4⁺ cells initiates immune response in which activated keratinocytes also take part. CD8⁺ T lymphocytes mediate the damage to the epidermis and leads to the characteristic lichenoid tissue reaction.

• There is evidence of the role of HLA-associated genetic susceptibility in the causation of the disease.
• A number of infections, mainly Hepatitis C virus infection are implicated in the triggering of LP.

CLINICAL FEATURES

• Lichen planus may affect all ages but is distinctly rare in children. Both sexes are affected with minor difference in the sex distribution at different ages.

• The chief complaint is usually intense pruritus. The itching associated with LP usually provokes rubbing of the lesions rather than scratching.

• The typical lesions of LP have the following features:

• The lesions have a characteristic violet hue.
• They are flat-topped , shiny, polygonal papules and plaques.
• The surface is dry with thin, adherent scales.
• A fine, white reticulated network, better visualized after application of oil on the surface, may be present on the surface (Wickham's striae)

• Thus, six 'p's characterize the lesions LP: they are planar, polygonal, purple, pruritic. papules and plaques.
   

• The lesions can occur anywhere on the body surface, the common sites are: front of the wrist and around the ankle. The lesions may remain localized to a few areas or there may be an acute eruption with appearance of lesions in crops. The lesions may remain discrete or may occur in groups which coalesce to form large irregular plaques.
• Fresh lesions may appear on scratch marks or at sites of other non-specific traumas (Koebner phenomenon)
• The lesions persist for a variable period of time and they eventually flatten often leaving prominent marks of pigmentation.
   
• CLINICAL VARIANTS OF LP: In many cases, the clinical picture may differ from the classical one, the variations being in morphology and configuration, or there may be modifications of clinical features by the site of involvement.       
  A. Variations in morphology:  
  • Hypertrophic LP: This may occur as the sole manifestation, or as part of a more generalized subacute disease. The lesions are elevated, warty, pigmented plaques typically occurring on the shin or around the ankle. These lesions tend to be persistent.
  • Atrophic LP: The lesions are few in number. There are depressed, pigmented lesions.
  • Follicular LP: Also known as lichen planopilaris, this may  accompany typical lesions or may be the sole morphologic type. There are small lesions centered around hair follicles. Lesions on scalp may result in alopecia. The combination of follicular LP with scarring alopecia of scalp and non-scarring alopecia of axilla and pubis or other areas is known as Graham-Little syndrome.
  • Actinic LP: Described mainly from the Middle East and India, these lesions are common on the face and presents as hyperpigmented patches with a surrounding zone of hypopigmentation.
  • Bullous LP: Vesicles and bullae may occur on typical lesions of LP in this variant due to severe basal cell degeneration induced by the inflammatory process.
  • Ulcerative LP: Chronic ulcers occur on the feet. May accompany loss of nails and oral ulcers.
  • LP pigmentosus: Described mainly from India and Middle East, these lesions present with deeply pigmented macules on the face and extremities

       B. Variations in shape:  

  • Linear LP: This may follow marks of injury by Koebnerization, or may occur spontaneously in long linear arrays, or rarely in a dermatome in a zoster-like fashion.
  • Annular LP: These lesions have central depressed areas with a raised margin. Typically occurs on penis
  • Guttate LP: Large number of drop-shaped lesions.

        C. Variations by site:
   

  • Oral: Oral lesions frequently occur in LP. They may take on various morphologic forms. The commonest variety is the erosive/ulcerative type which presents as persistent shallow erosions or ulcers over cheeks. The reticulated variety is the most characteristic lesion, presenting with whitish reticulated, lace-like patterns of oral mucosa. The plaque-type lesions commonly occur on the tongue and looks like areas of leukoplakia. Atrophic ,bullous and marginal gingival varieties also occur. Oral mucosal lesions are among the most chronic lesions of LP, often persisting for months or years together. Oral LP, particularly the chronic ulcerative variety is a potentially premalignant condition, sometimes leading to the development of squamous cell carcinoma.
  • Genital: Annular plaques often occur on the glans penis. Valval or vaginal lesions, often presenting with chronic ulcers, may rarely occur.
  • Nails: Nail dystrophies may occur in lichen planus, the various changes that may occur are: thinning of nail plate, longitudinal ridging, onycholysis, subungual hyperkeratosis and pterygium formation (fusion of proximal nail fold with the nail plate).
  • Palms and soles: Lichen planus of these locations lack the typical color: they are yellowish rather that violaceous papules and plaques.
  • Scalp: Follicular lesions are common here as well as areas of scarring alopecia.
     
•       D. Special variants:
   
  • Drug-induced lichenoid reactions: A number of drugs may induce development of lesions that clinically and histologically resemble idiopathic lichen planus.
    The principal offenders are: gold, penicillamine, beta-blockers, antimalarials. captopril, lithium, carbamazepine, chlorpromazine, thiazides, methyldopa, INH, PAS, and NSAIDs.
  • Lichen planus pemphigoides: Bullous lesions occur both on lesional as well as normal skin. This appears to be variant with combined features of LP and bullous pemphigoid.
  • Lichenoid contact dermatitis: Contact with color film developer containing paraphenyldiamine may give rise to LP-like lesions on hands. Amalgams in dental filling material may also give rise to lichenoid oral lesions.
  • Lichen planus-lupus erythematosus overlap: Lesions with atrophic center with violaceous border occur mainly of hands and feet. Immunohistologic evidence of both LP and LE are present.
     

    ASSOCIATIONS:   Some disorders are  associated with LP more frequently than is expected by chance:  

    • Vitiligo
    • Alopecia areata
    • Morphoea
    • Lichen sclerosus
    • Hepatitis C infection
    • Thymoma
    • Myaesthenia gravis
    • Ulcerative colitis
    • Primary biliary cirrhosis
    • Dermatomyositis

DIFFERENTIAL DIAGNOSIS

• Drug eruptions
• Psoriasis
• Discoid lupus erythematosus
• Secondary syphilis
• Lichen amyloidosus
• Viral warts
• Candidiasis
• Leukoplakia
• Pityriasis rosea
• Warty tuberculosis
• Graft versus host disease
• Papular mucinosis

DIAGNOSIS

Histopathologic features are supportive. The following findings, in combination, are characteristic of lichen planus:

• Hyperkeratosis without parakeratosis
• Hypergranulosis ( thickening of the granular layer )
• Irregular acanthosis with saw-tooth appearance of the rete-ridges
• Basal cell degeneration
• An upper dermal band-like lymphohistiocytic infiltrate that impinges on the epidermis, thus obliterating the dermo-epidermal interface. The lower border of the infiltrate is usually sharply defined.
• Presence of Civatte bodies ( also known as colloid bodies and  hyaline bodies), representing degenerated, apoptotic keratinocytes.

COURSE AND PROGNOSIS

• Lichen planus usually resolves by about a year's time. The cutaneous lesions gradually flatten and heals, often with unsightly post-inflammatory hyperpigmentation.
• Hypertrophic LP and oral mucosal LP are usually very chronic, persisting for months, or even years. Squamous cell carcinoma may develop from an ulcerative oral lesion.
• Nail changes and alopecia tend to be permanent.

TREATMENT

 Treatment is mainly symptomatic and tailored to individual cases.   Cutaneous Lesions:

• Topical steroids
• Intralesional steroids
• Antihistamines
• In generalized, severe cases: systemic steroids, PUVA therapy, Cyclosporine, or oral synthetic retinoids ( Acitretin)

Oral LP:

• Topical steroids
• Systemic steroids
• Topical retinoids
• Oral metronidazole
• Oral hydroxychoroquine
• Dapsone

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