[Lichen nitidus and lichen striatus]

Lichen nitidus is a rare, chronic dermatosis which occurs more often in children than in adults. It presents with tiny, monomorphous, lichenoid, mostly asymptomatic papules in regional or disseminated distribution which show a pathognomonic histological pattern. The pathogenesis is unclear; however, immunologic phenomena and genetic factors are under discussion. In rare cases, an association with other dermatoses and systemic diseases has been described. Moreover, medical treatments have been incriminated as triggers. Considering the self-limited course in mostly young patients, treatment must be thoroughly weighed. Possible therapeutic options include topical corticosteroids and calcineurin inhibitors as well as oral antihistamines, corticosteroids and narrow-band ultraviolet B phototherapy. Lichen striatus is an acquired, usually asymptomatic dermatosis occurring mostly in preschool children. The characteristic feature is the arrangement of small, flat, light red- to skin-colored papules along the lines of Blaschko. Therefore, a postzygotic mutation of epidermal progenitor cells induced to express new surface antigens by trigger factors as infections, vaccinations or trauma with consecutive immune reaction is assumed. Nail involvement of the affected limb can rarely occur. Lichen striatus usually heals without scarring within several months, so that therapies with severe side effects are obsolete. Mild topical corticosteroids or calcineurin inhibitors may be used, especially if patients exceptionally suffer from pruritus. A postinflammatory hypopigmentation can persist for months to years.