Fatal acute methotrexate intoxication resulting from medication error in a rheumatoid arthritis patient: a case report.

Methotrexate (MTX) has long been a first-line anti-rheumatic agent due to its efficacy and cost-effectiveness. While generally safe at the recommended weekly dosage of 5-25 mg for rheumatoid arthritis, medication errors can lead to acute toxicity, severe adverse effects, and potentially fatal outcomes. We report a case of a 51-year-old male who experienced fatal pancytopenia following an MTX medication error during treatment for rheumatoid arthritis. His blood MTX concentration measured 0.04 μmol/L 11 days after discontinuation. Postmortem examination revealed MTX-related toxicity in multiple organs, including the liver and intestines. The spleen showed a prominent increase in plasma cells, including numerous Mott cells. Forensic analysis established the cause of death as acute MTX intoxication, directly stemming from a chain of medical negligence involving prescribing, verification, and administration failures. This case underscores the necessity of rigorous therapeutic drug monitoring, individualized dosing, and robust systemic safeguards to prevent iatrogenic fatalities, highlighting its critical medicolegal and educational implications for forensic and clinical practice.