Lichen Striatus

Lichen striatus is a self-limited, unilateral eruption of small, flat topped, pink or flesh coloured papules that form a continuous or broken line along a limb or the trunk. It follows lines of embryonic skin development and mostly affects children.

It is most frequent between 5 and 15 years of age, with a female predominance, and is rare in adults. Clusters in spring and summer have been reported. It resolves spontaneously, usually within 6 to 24 months.

The cause is unknown. A genetic mosaic of keratinocytes is thought to become the target of a T-cell reaction after a trigger such as viral infection, trauma, vaccination or atopy. Recurrence is rare.

Pathophysiology.

A clone of epidermal cells carrying a postzygotic change follows the lines of embryonic skin development. A T-cell mediated interface reaction against these cells gives the lichenoid papules and the later pigment loss. Nail involvement occurs when the eruption crosses the nail matrix.

• Sudden onset of 1 to 3 mm shiny, scaly papules that coalesce into a band 2 to 30 cm long, mostly on one limb, less often on the trunk, neck or face.
• Mild or no itch, with no systemic upset.
• Postinflammatory hypopigmentation, particularly in darker skin, which can persist for months after the papules have gone.
• Nail involvement (ridging, splitting, onycholysis, loss of nail plate) when digits are affected.

• Clinical diagnosis from the linear, unilateral pattern and age.
• Dermoscopy shows erythema with fine scale and no white lacy striae.
• Biopsy only when the diagnosis is uncertain: a lichenoid and spongiotic reaction with a dense perivascular and periadnexal lymphocytic infiltrate.

Differential diagnosis. Linear lichen planus, inflammatory linear verrucous epidermal naevus, linear psoriasis, lichen nitidus, linear epidermal naevus, linear lichen sclerosus, linear porokeratosis and linear warts.

• Reassure the family that the condition is benign and resolves without scarring. Pigment change may take months to recover.
• Emollients. For itch or inflammation, a mild or moderate corticosteroid (hydrocortisone 1% or clobetasone butyrate 0.05%) once daily for 2 to 4 weeks.
• Tacrolimus 0.03% ointment twice daily on the face or flexures in children over 2 years, as a steroid sparing agent.
• Nail disease usually recovers without treatment, and short term topical steroid on the nail fold may help.
• Treatment shortens the course only slightly, and evidence is weak.

Monitoring. Review at 3 months. Re-evaluate if lesions persist beyond 2 years or become widespread.

Referral and escalation. Refer to dermatology if the diagnosis is uncertain or the eruption persists.

Special groups. In children avoid potent steroids on the face and flexures.