Pneumocystis jirovecii pneumonia induced by low-dose methotrexate in a patient with chronic urticaria

Abstract Methotrexate has immunosuppressive effects and is administered for refractory chronic urticaria. We present a case of Pneumocystis jirovecii pneumonia in a patient with refractory chronic urticaria managed by low-dose weekly methotrexate treatment (total cumulative dose 195mg). Our study highlights the importance of providing prompt diagnosis and treatment of Pneumocystis jirovecii pneumonia in patients with chronic urticaria under methotrexate therapy.