Pancytopenia as a Complication of Low-Dose Methotrexate in a Septuagenarian: A Rare Presentation.

Methotrexate (MTX) is an antimetabolite that was initially developed as a chemotherapeutic agent to treat malignancies but later used extensively to treat rheumatological conditions. MTX-induced toxicity is dose- and duration-dependent. Myelosuppression is a rare but fatal complication of MTX that can occur even with low doses used for inflammatory conditions. Multiple factors such as age, renal impairment, and nutritional status increase the risk of developing MTX toxicity. Frequent monitoring of symptoms and lab values are the hallmarks of prompt diagnosis and prevention of complications. Clinicians should have a high degree of suspicion to diagnose pancytopenia secondary to MTX especially in patients with multiple confounding comorbidities. We present the case of a 79-year-old male who presented with mucositis and pancytopenia diagnosed to be secondary to weekly MTX for giant cell arteritis leading to anemia and septic shock causing death.