Actinic Lichen Planus

Actinic lichen planus is an uncommon photodistributed variant of lichen planus, with annular or pigmented plaques on sun exposed skin of the face, neck, dorsal hands and forearms. It is a disease of warm climates and darker skin.

It occurs mostly in young adults from the Middle East, South Asia and Africa, with onset in spring and summer. There is no clear sex predominance.

Subtypes are annular (a hyperpigmented rim with a pale centre), dyschromic (melasma like), and pigmented plaque. Ultraviolet radiation acts as the trigger, and mucosal and nail involvement are rare.

Pathophysiology.

Ultraviolet light is thought to create new antigens or change keratinocytes, provoking a cytotoxic T-cell interface reaction in exposed skin. Pigment incontinence from basal cell damage produces the hyperpigmentation.

• Annular plaques of 1 to 4 cm, with a hyperpigmented, slightly raised rim and a hypopigmented or atrophic centre, mostly on the face, neck and extensor forearms.
• Dyschromic type: brown, melasma like patches on the face. Pigmented plaque type: brown black plaques on exposed skin.
• Mild or no itch, with a seasonal pattern and worsening with sun.
• Healing with postinflammatory pigment change, with little scarring.

Red flags.

• Rapidly spreading or ulcerated lesions.
• Persistent facial plaques failing to respond, raising concern for another diagnosis such as lupus.
• Mucosal erosions, suggesting classic erosive lichen planus.

• Clinical, with biopsy to confirm: interface dermatitis with band like lymphocytes, basal vacuolar change, melanophages, and wedge shaped hypergranulosis.
• Phototesting if a photosensitive condition is considered.
• Antinuclear and anti-Ro antibodies when lupus is in the differential.
• Hepatitis C serology and drug review, since the associations are those of classic lichen planus.

Differential diagnosis. Melasma, granuloma annulare, discoid lupus erythematosus, polymorphic light eruption, annular lichen planus, erythema dyschromicum perstans, sarcoidosis and tinea.

• Strict photoprotection with a broad spectrum sunscreen (sun protection factor 50 or more with ultraviolet A protection), clothing and shade. Avoid phototherapy, which can aggravate the disease.
• Potent topical corticosteroid (betamethasone valerate 0.1%) once daily on the body for 4 to 6 weeks, and moderate potency (clobetasone butyrate 0.05%) on the face for up to 2 weeks.
• Tacrolimus 0.1% ointment twice daily on the body, or 0.03% on the face, for maintenance.
• Hydroxychloroquine 200 mg twice daily within a limit of 5 mg/kg/day of real body weight, for 3 to 6 months. Arrange baseline retinal screening, and annual screening after 5 years of use or sooner with risk factors such as kidney disease.
• Resistant disease: acitretin 25 to 50 mg daily, or prednisolone 0.5 mg/kg/day (usually 30 to 40 mg) for 2 to 3 weeks with tapering. Acitretin is teratogenic, and strict contraception is required during treatment and for 3 years after.
• Depigmenting or camouflage measures can be offered for residual pigment change.

Monitoring. Review every 4 to 8 weeks. Check liver tests and lipids on acitretin.

Referral and escalation. Refer to dermatology for biopsy, and for refractory or extensive disease.

Special groups. Hydroxychloroquine dose reductions are needed in kidney impairment. Acitretin is contraindicated in pregnancy.