Abstract: @@ Dapsone syndrome is characterized by high fever, skin rash, methemoglobinemia, liver toxicity, and generalized lymphadenopathy. The incidence of the dapsone syndrome is increasing with the extensive application of dapsone. However it is rarely reported in pemphigus. We present a case of "infectious mononucleosis-like" dapsone syndrome in a patient with pemphigus vulgaris. The syndrome appeared when he was being treated methylprednisolone, which was commonly used as a treatment for dapsone syndrome.