1.5.4 Lichen planus

Synonyms

Lichen ruber planus. 

Epidemiology

Prevalence between 0.1 to 4%, with most cases occurring between 30 to 60 years of age, and with a slight predominance in perimenopausal women. 

Definition

Idiopathic subacute to chronic inflammatory dermatosis involving the skin, mucosae, nails and/or hair.

Aetiology & Pathogenesis

Very likely to be an autoimmune disorder, associations with collagen-vascular diseases, vitiligo and diabetes mellitus. Graft-versus-host-disease (GvHD) has similar morphology. Hepatitis B and C, stress and various drugs may also play a role in its induction.

Signs & Symptoms

  1. Skin: polygonal violaceous papules, white net-like superficial markings (Wickham's striae), marked pruritus; Köbner phenomenon.
  2. Mucosae: lips, tongue, cheeks, genital and anal areas (annular, bullous, erosive, atrophic), net-like white, non-removable pattern.
  3. Nails: nonspecific changes (longitudinal stripes), nail dystrophy, nail matrix destruction.
  4. Scalp: lichen planopilaris, atrophic scarring alopecia.
  5. Palmoplantar: hyperkeratosis and fissures.

Localisation

More commonly flexor aspects of wrists, nails, oral and genital mucosae; can be disseminated.

Classification

Various types: localized, exanthematous, mucosal.

 

Laboratory & other workups

None specific. 

Dermatopathology

Acanthosis, saw-toothed dermal-epidermal junction profile, hypergranulosis, subepidermal interface band-like infiltrate of T lymphocytes, pigment incontinence.

Course

Lichen planus of the skin often resolves after a few months or years, although it may recur. If caused by medication or tooth fillings, lichen planus will clear after the treatment is stopped or the fillings removed. Lichen planus of the mucosa, nails, and scalp rarely clears by itself and can cause permanent scarring. 

Complications

Erosive lichen planus of the mucosae can lead to squamous cell carcinoma, making follow-up essential.

Diagnosis

Clinical features, histology, Köbner phenomenon.

Differential diagnosis

Lichenoid drug reactions: Skin eruptions caused by commonly used medications can resemble lichen planus. Quinine in tonic water and over-the-counter leg cramp medicines can cause a lichen planus–like condition. In the mouth, allergy to the metals in fillings and oral appliances can cause sores that look exactly like oral lichen planus.

Prevention & Therapy

Prevention: Avoid/control predisposing factors.

  • Topical: high potency corticosteroids, calcineurin inhibitors (mucosal involvement), tazarotene, calcipotriol, UVA/B, PUVA, UVA1.
  • Systemic: corticosteroids, PUVA, dapsone, hydroxychloroquine, methotrexate, mycophenolate mofetil, acitretin, alitretinoin, ciclosporin, azathioprine, apremilast, sedatives.

Special

TNF blockers exhibit fairly controversial effects in lichen planus, since they can trigger proinflammatory reactions. 

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