Lichen striatus

Lichen striatus is a rare, self-limiting, inflammatory, linear dermatosis that occurs mainly in children. It presents as pink or skin-coloured papules that join together to form one or more dull red or hypopigmented, slightly scaly, linear bands.

This chapter is set out as follows:

• The cause is unknown
• The eruption affects Blaschko's lines, which are embryonic in origin

• More than 50% of cases occur in children aged 5-15 years, it is rare in adults
• Females are affected two to three times more frequently than males
• It is usually asymptomatic but some patients may complain of itching

Distribution

• Lesions are usually unilateral and solitary, the line is often irregular 

• The proximal limbs, followed by the neck, are the most commonly affected sites. Sometimes a band may extend from the leg onto the buttock or abdomen. The face and trunk are less frequently affected 

• Lesions run along the lines of Blaschko, which take on the patterns described below. For more information on Blaschko's lines refer to the related chapter
• Arms and legs - linear or whorled (spiral), roughly parallel with long axis of the limbs
• Trunk - they differ from dermatomes in being more numerous and wave-like on the lateral trunk, and V-shaped in the middle of the back. Anteriorly they never cross the midline. Posteriorly the midline is often shifted from the anatomical midline
• Face - vertical in the mid-face, laterally from the angles of mouth

• Much less commonly lesions may be bilateral, occur in multiple parallel bands, or be zosteriform in pattern

Morphology

• Lichen striatus presents abruptly as small, pink or skin-coloured papules that join together over a period of 1-2 weeks to form a dull red slightly scaly linear band that may be continuous or interrupted. Occasionally there are vesicular components. Lesions can be hypopigmented in dark-skinned individuals 

• The band ranges from a few mm to several cm in width, and may be several cm in length or extend the entire length of the limb. The lesion usually reaches its maximum length within three weeks, although occasionally there can be gradual extension for several months 

• Lichen striatus may resolve with postinflammatory hyper or hypopigmentation

• Nail involvement is very uncommon, and has been reported without skin lesions. Usually only one nail is involved, changes include longitudinal ridging, splitting, hyperkeratosis of the nail bed, onycholysis, and nail loss 

• The main differential diagnoses are the other linear dermatoses that run along Blaschko's lines, especially an inflammatory linear verrucous epidermal naevus (ILVEN), however, when compared to lichen striatus, ILVEN have the following characteristics:
  • 75% of lesions arise during the first five years of life, most often in the first six months
  • They have a more gradual onset, and are more itchy 
  • Lesions are often very persistent 

• Lichen striatus is self-limiting, spontaneously regressing within 3-12 months, and as such no treatment is usually required

• Emollients and/or topical steroids may be used if the skin is itchy, the latter may speed up resolution of the rash. Tacrolimus ointment and pimecrolimus cream have been reported as successful in treating persistent and pruritic lesions on the face and extremities