A 38-year-old woman presents to her primary care physician with a 6-month history of fatigue. However, in the past week, she has begun feeling short of breath, even walking to the grocery store, something she was able to do easily before. She also reports a history of rheumatoid arthritis, for which she takes prescribed pain killers. She does not smoke or drink alcohol. On examination, mucosal pallor is present, but vital signs are normal. Laboratory results are as follows-
Peripheral blood film examination- normocytic anemia
Serum iron: 38 µg/dL (normal 50-170 µg/dL)
TIBC: 225 µg/dL (normal 250-450 µg/dL)
Transferrin saturation: 10% (normal 15- 50%)
Serum ferritin: 190 µg/L (normal 15-150 µg/L)
Which of the following is a likely cause of this patient’s anemia?