ABSTRACT

Methotrexate (MTX) is a folic acid antagonist that limits the amount of tetrahydrofolate which is required in the synthesis of purine. In general, high dose MTX is used in leukemias and lymphomas while a low dose is used in the treatment of some rheumatic diseases for immunosuppressive purpose. The side effects caused by high doses of MTX are less common in low doses. Known side effects are bone marrow suppression, oral and gastrointestinal ulcers, hepatotoxicity, and pulmonary fibrosis. In this article, we reported a patient taking low-dose oral MTX for 9 months because of the diagnosis of psoriatic arthritis in whom pancytopenia, delirium, fever, and gastrointestinal side-effects developed and then all of the findings disappeared after MTX is ceased and folinic acid rescue treatment was performed.