Lichen striatus (LS), also known as Blaschko linear acquired inflammatory skin eruption, or linear lichenoid dermatosis, is a benign, rare and self-limiting inflammatory skin condition.
It primarily affects children between the ages of 5 to 15 years, but can occur at any age.
LS initially presents as pinkish-red or flesh-colored spots, formed by scaly flat-topped papules, that coalesce over a two-week period, or less, to form a dull scaly linear band.
The lesion associated with LS tends to occur more frequently on an extremity (i.e. the arm or leg); however, it may also affect the neck, torso or buttocks.
While LS predominantly affects the the skin, it may also occur on the nails. It arises over a period of weeks to months, and slowly fades over a year or less.
The skin over the lesion may show pigmentary changes which persist for a few years.
Etiology and pathogenesis
The exact cause of LS is unknown. There is no racial predilection for LS. While some studies suggest that its incidence is higher among girls, others have shown a fairly equal distribution between the sexes. The median age of onset is around 3 years.
There are some indications of a T-cell-mediated inflammation which forms the basis for LS.
Likewise, it has been suggested by other researchers that the condition may have possible genetic or environmental triggers, such as trauma and/or infections, that play a role in its development.
Atopy (a genetic tendency to develop allergic diseases) is believed to be a strong predisposing factor associated with the development of LS.
Several studies have indicated that many patients with LS also have a positive personal or family history for allergic rhinitis, asthma or atopic dermatitis.
These studies, however, have been criticized by other workers, who conclude that the incidence of atopy in this patient group is not significantly higher than that seen in the general population.
In addition, research points to the possibility of LS being related to an autoimmune-mediated process occurring during the fetal life of the subject.
LS lesions follow the lines of Blaschko; hence the name. These lines are presumed to be embryonic in origin.
They are thought to be due to the segmental growth of cutaneous cells, or mosaicism of these cells, induced by a mutation that resulted from a triggering event early during embryogenesis.
This trigger could have been a viral infection. This suggestion has been accepted over the years, and the Blaschko line distribution has both topographic and pathogenetic significance.
As with many studies, there is a difference of opinion with regard to the actual meaning of the relationship of the Blaschko line to LS.
Some research points to the implication of an axial-neural phenomenon in the condition.
Management and treatment
Treatment for LS is usually not necessary, because it is self-limited. It resolves usually within a period of 3 to 12 months.
Resolving lesions may leave a transient hypopigmented or hyperpigmented mark that gradually returns to the original skin color.
Oils or creams may be used to control skin dryness and itching. Topical steroids may also be employed, but these take some time before their effects are noticeable. Other therapies involve the photodynamic use of methyl aminolevulinic acid.