When things don't add up ‐ methotrexate unexpectedly revealed as the cause of pancytopenia

A 24-year-old woman presented with acute onset of pancytopenia and infectious complications, including Staphylococcus aureus bacteremia. Iatrogenic myelosuppression from lamotrigine, prescribed for bipolar affective disorder, was suspected. Her counts normalized upon cessation of lamotrigine together with filgrastim (G-CSF) therapy. However, she presented again 6 weeks later with a neutropenic fever and mouth ulcers. Blood counts on admission...