Does hydroxyethyl starch cause lichen planus? Lichen planus in a long-time routine blood donor never exposed to hydroxyethyl starch.

A case of lichen planus attributed to exposure to hydroxyethyl starch has been reported previously. In this report, a case of lichen planus in a healthy blood donor never exposed to hydroxyethyl starch is presented, the statistical incidence of lichen planus in healthy leukapheresis donors is approximated, and a description of the Koebner phenomenon, which could falsely lead to incorrect conclusions regarding cause and effect in this disease, is discussed.