Stevens-Johnson syndrome-like exanthema secondary to methotrexate histologically simulating acute graft-versus-host disease

A 61 year old male patient suffering from psoriasis vulgaris developed a se vere skin reaction with toxic myelosuppression three days after administrat ion of 20 mg methotrexate (MTX) p.o, per week and concomitant 100 mg acetyl ic salicylic acid (ASA) per day. The skin lesions simulated Stevens-Johnson syndrome with ulcerations of the oral mucose and erythema multiforme-like target lesions. The histology of the epidermis resembled an acute graft-ver sus-host reaction. The increased toxic effect of MTX on keratinocytes in ou r patient was most likely caused by a lowered plasma binding capacity and r educed renal excretion of MTX due to concomitant administration of ASA. Thu s in the treatment of severe forms of psoriasis with MTX, the combined admi nistration of drugs aggravating MTX toxicity, particularly of ASA, should b e carefully considered, due to the increased toxicity and risk of seven ski n reactions.