Hypertrophic Lichen Planus

Hypertrophic lichen planus is a variant of lichen planus with thick, hyperkeratotic, violaceous or brown plaques, most often on the shins and ankles, and with intense itch. It is chronic and can persist for years.

Lichen planus affects about 0.2 to 1% of people, mostly in middle age, and the hypertrophic form is a minority, most frequent in men. It is more common in people with hepatitis C infection.

Triggers and associations include hepatitis B and C, drugs (angiotensin converting enzyme inhibitors, thiazides, beta blockers, non-steroidal anti-inflammatory drugs, antimalarials and gold), contact allergy to metals, and stress. A small proportion of long standing hypertrophic plaques develops squamous cell carcinoma.

Pathophysiology.

Cytotoxic T cells attack basal keratinocytes in an interface reaction. Chronic scratching causes epidermal thickening, hypergranulosis and hyperkeratosis, and the dermal infiltrate is band like. Persistent antigen exposure and local trauma sustain the hypertrophic form.

• Thick, verrucous, hyperkeratotic purple brown plaques on the shins, ankles and dorsal feet, often with surrounding classic flat topped papules.
• Marked itch, with excoriation and lichenification.
• Healing with hyperpigmentation and, sometimes, scarring.
• Lichen planus at other sites (mouth, genitals, nails, scalp) in some patients.

Red flags.

• Rapidly growing, ulcerating or bleeding plaque, suggesting squamous cell carcinoma.
• Long standing plaques with a firm nodule.
• Scarring alopecia or erosive mucosal disease.

• Skin biopsy, with a deep punch or incisional specimen: marked hyperkeratosis, irregular acanthosis, hypergranulosis, and a band like lymphocytic infiltrate with basal damage.
• Hepatitis B and C serology, and HIV test.
• Drug history and review, and patch testing if a metal or other allergen is suspected.
• Examination of the mouth, genitals, nails and scalp.

Differential diagnosis. Lichen simplex chronicus, prurigo nodularis, squamous cell carcinoma, Bowen disease, verruca vulgaris, hypertrophic discoid lupus, lichenoid drug eruption, psoriasis and stasis changes.

• Very potent topical corticosteroid (clobetasol propionate 0.05%) once or twice daily, under occlusion, for 4 to 6 weeks, then reduce to intermittent use.
• Intralesional triamcinolone acetonide 5 to 10 mg/mL, injected at 0.1 mL at each site every 3 to 4 weeks, with a maximum of 20 mg at a session.
• Acitretin 25 to 50 mg daily for 3 to 6 months for refractory disease. It is teratogenic, and women of childbearing potential must avoid pregnancy during treatment and for 3 years after stopping.
• Narrowband ultraviolet B or psoralen with ultraviolet A phototherapy two to three times weekly.
• Methotrexate 7.5 to 15 mg once weekly (maximum 25 mg) with folic acid 5 mg weekly, or ciclosporin 2.5 to 5 mg/kg/day in two divided doses, for refractory disease.
• Prednisolone 0.5 mg/kg/day (usually 30 to 40 mg) for 2 to 3 weeks with tapering is used only for severe, generalised disease.
• Sedating antihistamine such as chlorphenamine 4 mg at night for itch. Cryotherapy may help isolated plaques.

Monitoring. Review every 4 to 8 weeks. For acitretin, monitor lipids and liver tests. Biopsy any plaque that changes, ulcerates or fails to respond.

Referral and escalation. Refer to dermatology for biopsy and systemic treatment, and urgently for suspected malignancy.