Mixed diagnoses – 10 cases (7 of 11)

This is lichen striatus, an uncommon unilateral skin disorder of unknown cause. It is more common in children, females being affected twice as frequently as males. It presents as pink papules coalescing into one or more parallel linear streaks which may become hypopigmented or hyperpigmented before disappearing spontaneously weeks to months later.

Linear lesions may be congenital, the result of scratching (isomorphic response or Koebnerisation), due to contact with material which has streaked on the skin, or arise for unknown reasons.Linear naevi include:

• Epidermal naevi
• Naevoid hypo- or hypermelanosis
• Linear porokeratosis

Koebnerising skin disorders include:

• Psoriasis
• Lichen planus
• Eczema
• Vitiligo
• Viral warts

Unexplained linear lesions occur in:

• Scleroderma
• Lichen sclerosus

Exogenous cause

• Contact dermatitis eg to plant or perfume
• Artefact or injury