A 67-year-old woman with long-standing rheumatoid arthritis reports increasing fatigue and reduced exercise tolerance. Her haemoglobin is 92 g/L (115–155), mean corpuscular volume is 72 fL (80–100), and reticulocyte count is low; the serum ferritin is 240 microgram/L (15–200), transferrin is reduced and C-reactive protein is markedly increased. Which one of the following is the most likely diagnosis?