Presented by: Lauren Ogrich, MD and Carrie Ann Cusack, MD
Drexel University College of Medicine
May 16, 2016
Blaschkoid dermatoses are generally congenital dermatoses, although many acquired blaschkoid dermatoses have been described including lichen striatus, linear lichen planus, and adult blaschkitis. Linear psoriasis was first described in 1951. There has been considerable debate regarding whether linear psoriasis exists as a distinct entity or if it represents inflammatory linear verrucous epidermal nevus (ILVEN) or psoriasis superimposing on an epidermal nevus. ILVEN tends to occur during the first years of life, whereas linear psoriasis tends to occur in adulthood. Immunohistopathologic studies suggest there is lower expression of keratin 10 in psoriasis while ILVEN has lower levels of T-cell surface expression markers including CD8, CD45RO, CD2, CD94, and CD161. Involucrin expression also tends to be absent in ILVEN.
It has been proposed that linear psoriasis occurs via somatic recombination. Therefore, an individual with linear psoriasis is heterozygous for several genes predisposing to psoriasis and undergoes crossing over in a somatic cell during embryogenesis resulting in a daughter cell with genetic mosaicism. The linear psoriatic eruption would then occur in the presence of other predisposing genes and environmental factors.
Historically, ILVEN tends to be refractory to treatment whereas linear psoriasis tends to respond well to typical anti-psoriatic mediations. Successful treatment of linear psoriasis in the literature includes topical steroids, topical dithranol, methotrexate, and infliximab.
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