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Functional Iron Deficiency RA — SCE Rheumatology MCQ

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HardRheumatoid ArthritisFunctional Iron Deficiency RASCE Rheumatology

A 60-year-old woman with active rheumatoid arthritis has persistent anaemia. Her haemoglobin is 98 g/L, mean corpuscular volume 82 fL, C-reactive protein 55 mg/L, ferritin 180 micrograms/L and transferrin saturation 12%. Her soluble transferrin receptor/log ferritin index is 0.7. Reticulocyte count, bilirubin, lactate dehydrogenase, haptoglobin, vitamin B12 and renal function are normal. Which diagnosis best explains this pattern?

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Correct answer: D — Anaemia of inflammation with functional iron restriction

The diagnosis is **anaemia of inflammation with functional iron restriction**. Active RA drives IL-6-mediated hepcidin production. Hepcidin reduces ferroportin-mediated iron export from macrophages, hepatocytes and enterocytes, so circulating iron and transferrin saturation fall despite preserved total-body iron stores and normal or raised ferritin. A soluble transferrin receptor/log ferritin index below 1 further supports rheumatoid anaemia rather than absolute iron depletion. Absolute iron-deficiency anaemia usually raises soluble transferrin receptor and its ferritin index, although ferritin alone can be misleading during inflammation. Vitamin B12 deficiency would usually be macrocytic and is excluded biochemically. Haemolysis would produce reticulocytosis and abnormal bilirubin, LDH or haptoglobin. Myelodysplasia is not supported by the inflammatory iron profile or by any reported macrocytosis or cytopenias.

Reference: Masson C. Rheumatoid anemia. Joint Bone Spine. 2011;78(2):131-137. https://pubmed.ncbi.nlm.nih.gov/20851655/