A 45-year-old woman with rheumatoid arthritis begins methotrexate. Six weeks later she has mouth ulcers and macrocytosis. She has not been taking the

Question

A 45-year-old woman with rheumatoid arthritis begins methotrexate. Six weeks later she has mouth ulcers and macrocytosis. She has not been taking the prescribed supplement. Which of the following is the most likely explanation for this patient's findings?

Accepted Answer

Folate antagonism from methotrexate

Answer

Excess iron absorption

Answer

Histamine release from mast cells

Answer

Increased purine synthesis

Answer

Vitamin B12 toxicity

Methotrexate adverse effect — USMLE Step 3 MCQ

A 45-year-old woman with rheumatoid arthritis begins methotrexate. Six weeks later she has mouth ulcers and macrocytosis. She has not been taking the prescribed supplement. Which of the following is the most likely explanation for this patient's findings?