Main inflammatory mediator in anaemia of chronic disease
**Core Concept**
Anaemia of chronic disease (ACD) is a condition characterized by a decrease in iron availability, leading to impaired erythropoiesis, despite adequate or increased iron stores. This condition is often seen in patients with chronic infections, autoimmune diseases, or malignancies. The main inflammatory mediator in ACD plays a crucial role in modulating the immune response and influencing the production of inflammatory cytokines.
**Why the Correct Answer is Right**
The main inflammatory mediator in ACD is **hepcidin**. Hepcidin is a peptide hormone produced by the liver that regulates iron metabolism by inhibiting the absorption of dietary iron and the release of iron from macrophages. During chronic inflammation, hepcidin levels increase, leading to a decrease in available iron for erythropoiesis. This results in the characteristic features of ACD, including reduced serum iron, increased ferritin, and decreased transferrin saturation. The increased hepcidin levels also contribute to the decreased expression of transferrin receptor 1 on the surface of erythroid precursors, further impairing iron uptake.
**Why Each Wrong Option is Incorrect**
**Option A:** Interleukin-6 (IL-6) is an inflammatory cytokine involved in the acute phase response, but it is not the primary mediator of iron metabolism in ACD.
**Option B:** Tumor necrosis factor-alpha (TNF-alpha) is another pro-inflammatory cytokine that contributes to the pathogenesis of ACD, but it is not the main mediator of iron metabolism.
**Option C:** Interleukin-1 beta (IL-1Ξ²) is involved in the inflammatory response and can contribute to the production of hepcidin, but it is not the primary mediator of iron metabolism in ACD.
**Clinical Pearl / High-Yield Fact**
Hepcidin is often referred to as the "iron brake" because of its role in regulating iron availability during chronic inflammation. A key clinical correlation is that patients with ACD often require iron supplementation to correct their anaemia, despite having adequate or increased iron stores.
**Correct Answer:** C. Hepcidin.