Methotrexate (MTX) Induced Pancytopenia - A Rare Serious Adverse Effect

ABSTRACT

A 65-year-old woman presented to us with complaints of fatigability and appearance of red spots on extremities since 6 days. She was a known case of rheumatoid arthritis since 5 years and was on tablet prednisolone 5 mg OD and tablet hydroxychloroquine 200 mg bid orally. Two months back she had exaggerated symptoms in the form of increased joint pains for which tablet methotrexate 7.5 mg was started weekly once and was increased to 7.5 mg bid (15 mg) per week 2 weeks back along with folic acid 5 mg per day.Methotrexate (MTX) is a folate antagonist used to treat various malignancies, and autoimmune disorders including rheumatoid arthritis. It enters cell by an active cellular uptake and inhibits dihydrofolate reductase (DHFR) enzyme that converts dihydrofolate (DHF) to tetrahydrofolate (THF) affecting purine and ultimately DNA synthesis. Cell with capability of polyglutamylation like myeloblasts and lymphoblasts are most susceptible to the effects of MTX because polyglutamylation prolongs its intracellular presence.1,2