A 42-year-old man with a 10-year history of rheumatoid arthritis and a 5-year history of chronic kidney disease (eGFR 35 mL/min/1.73 m²) presents with hemoglobin 9.2 g/dL and normocytic indices. Serum iron and ferritin are normal. What is the most common cause of anemia in this patient?

Explanation

## Anemia of Chronic Disease: Most Common in This Context **Key Point:** In patients with multiple chronic conditions (rheumatoid arthritis + chronic kidney disease), anemia of chronic disease (ACD) is the most common cause, not iron deficiency or other specific anemias. ### Pathophysiology of Anemia of Chronic Disease ```mermaid flowchart TD A[Chronic Inflammation/CKD] --> B[Increased IL-6, TNF-α, IL-1] B --> C[Increased Hepcidin] C --> D[Decreased Iron Absorption] C --> E[Decreased Iron Release from Macrophages] D --> F[Functional Iron Deficiency] E --> F F --> G[Decreased RBC Production] A --> H[Decreased Erythropoietin] H --> G G --> I[Normocytic Anemia] ``` ### Diagnostic Features of ACD | Feature | Finding | |---------|----------| | **Hemoglobin** | 8–11 g/dL (mild-moderate) | | **MCV** | Normocytic (80–100 fL) | | **Serum iron** | Low or normal | | **Ferritin** | Normal or elevated | | **TIBC** | Normal or low | | **Transferrin saturation** | Low | | **Reticulocyte count** | Low (inappropriate for degree of anemia) | **High-Yield:** The combination of **normal ferritin + normocytic anemia + chronic disease** is diagnostic of ACD. This distinguishes it from iron deficiency (low ferritin, microcytic). ### Contributing Factors in This Patient 1. **Rheumatoid arthritis:** Chronic inflammatory state → IL-6 production → hepcidin ↑ 2. **Chronic kidney disease:** Decreased erythropoietin production → reduced RBC synthesis 3. **Combined effect:** Both mechanisms contribute to normocytic anemia **Clinical Pearl:** ACD is the second most common cause of anemia overall but becomes the most common in patients with multiple chronic conditions. It is often overlooked because it is "mild" and attributed to other causes. ### Why Not Iron Deficiency Here? - Ferritin is normal (not low) - TIBC is not elevated - No evidence of blood loss - Microcytic pattern is absent