[Coincidence of light urticaria and lichen ruber planus].

A 49-year-old patient with concomitant solar urticaria (SU) and lichen planus (LP) is presented. The sunlight- and UV-A-provoked wheal and flare SU reactions were interpreted as an antigen-antibody reaction, probably involving a reaginic antibody, because SU was passively transferred by a serum factor utilizing the Prausnitz-Küstner reaction. The reduced percentage of suppressor cytotoxic T-cell subset in peripheral blood typical of active LP may facilitate the increased production of reaginic antibodies after presentation of antigen by sunlight. Not only was the usual immunological reaction of LP (similar to graft-versus-host reaction) suppressed by PUVA treatment, but increased tolerance to sunlight was also achieved.