Diagnosis

Lichen planus

Etiology

Cause [aue][rd9]

• Precise cause is unknown

• A possible explanation is an abnormal immunological reaction to different exogenous agents such as viruses, drugs, or contact allergens [aue]

• Drug-induced lichen planus (lichenoid drug eruption) can resemble idiopathic lichen planus

Pathophysiology [aue][rd9]

• Cytotoxic CD8 T cells recognize an unknown antigen causing destruction of keratinocytes

Complications [iom][aue]

• Scarring

• Stricture

• Post-inflammatory hyperpigmentation

• Onychodystrophy

• Malignant transformation into squamous cell carcinoma

• Secondary infection

Epidemiology

Incidence per 100.000 [iom][35c][f1t][uru]

Prevalence per 100.000 [iom][35c][f1t][uru]

Approach

• Clinical diagnosis: [iom]

  • Skin lesions: Itchy, violaceous papules/plaques

  • Location: Wrists, lower back, ankles, oral mucosa (rarely affects the vulva, the vagina, the pharynx, the larynx, and the oesophagus)

  • Wickham’s stria (white lines) are pathognomonic of the condition [35c]

• Biopsy

Treatment

The condition is self-limited and generally lasts 6–24 months [35c][aue]

1. Symptomatic treatment:

   • Avoid: spicy/acidic food, alcohol, tobacco

   • Antihistamine (pruritus)

   • Steroid cream twice daily for 2 to 4 weeks

   • Intralesional steroid injections (triamcinolone 5 to 10 mg/mL)

2. First-line therapy:

   • Oral corticosteroids (prednisone 30 to 60 mg) tapered over 2 to 6 weeks

3. Second-line therapy: [aue]

   • Metronidazole (500 mg twice daily for 3 to 8 weeks)

   • Sulfasalazine (500 mg twice daily increased until 2.5 grams daily, for 3 to 6 weeks)

   • Isotretinoin (10 mg twice daily for 2 months)

   • Acitretin (30 mg daily for 8 weeks)

   • PUVA, UVB

   • Topical calcineurin inhibitors

   • Methotrexate (15 mg per week for adults, 0.25 mg/kg per week for children)

4. Third line therapy: Trimethoprim-sulfamethoxazole, griseofulvin, terbinafine, antimalarials, tetracyclines, ciclosporin, mycophenolate mofetil, azathioprine, etanercept, adalimumab, or low-molecular-weight heparin [aue]

Differential diagnoses

Candidiasis, Cutaneous T-cell lymphoma, Drug side effects, Eczema, Graft-versus-host disease, Lichenoid keratosis, Lichen sclerosus, Paget's disease, Parapsoriasis, Pityriasis lichenoides, Pityriasis rosea, Pityriasis rubra pilaris, Pityriasis versicolor, Psoriasis, Squamous cell carcinoma, Syphilis, Systemic lupus erythematosus, Tinea corporis