Lichen striatus after interferon therapy

INTRODUCTION A variety of cutaneous reactions have been described in patients receiving tumor necrosis factor alfa (TNF-a) inhibitors. Of particular interest in this scenario is the development of lichen planus and lichen planuselike eruptions. Because TNF-a is recognized as a significant factor in the induction of these dermatoses, their appearance after inhibition of TNF-a is perplexing. The leading theory postulates that a disturbance in the balance between inflammatory cytokines occurs with TNF-a inhibition, leading to increased expression of other cytokines such as interferon. Interferon then induces an endogenous inflammatory response that clinically manifests as a cutaneous lichenoid eruption. Lichen striatus is an acquired inflammatory dermatosis that follows the lines of Blaschko. Blaschko lines are invisible in normal skin but may become apparent in various skin conditions. It has been postulated that the cells along Blaschko lines contain distinct genotypes that may ultimately permit a unique response to stimuli such as interferon. This heightened sensitivity to interferon is likely the underlying explanation for the appearance of segmental lichenoid reactions after treatment with TNF-a inhibitors. However, reports of these eruptions after interferon are lacking, and the evidence to support this concept is primarily substantiated by reports of segmental lichenoid reactions after anti-TNF agents.