Anemia of Chronic Disease

Anemia of chronic disease (ACD), also called anemia of inflammation, is the second most common cause of anemia after iron deficiency anemia and arises in patients with chronic inflammatory disease, chronic infection, or malignancy. Inflammatory cytokines (particularly interleukin-6) drive hepatic production of hepcidin, the master regulator of iron homeostasis, which blocks intestinal iron absorption and traps iron inside macrophages and other reticuloendothelial cells — iron is available in the body but functionally withheld from erythropoiesis. This distinguishes ACD from true iron deficiency, where total body iron is genuinely depleted, and the distinction matters clinically because standard oral iron is largely ineffective in ACD (the same hepcidin block that traps existing iron stores also blocks absorption of any new oral iron) while addressing the underlying inflammatory condition is the primary, and sometimes only, effective strategy.^[1]

Anemia is typically mild to moderate and normocytic (sometimes mildly microcytic), and its symptoms — fatigue, reduced exercise tolerance, pallor — are frequently attributed to the underlying chronic disease itself rather than recognized as a separate, partially treatable contributor to how unwell the patient feels. ACD is common in rheumatoid arthritis and other chronic inflammatory arthritides, inflammatory bowel disease, chronic kidney disease, chronic infection (including HIV and tuberculosis), and malignancy.

• Any chronic inflammatory disease: rheumatoid arthritis, systemic lupus erythematosus, inflammatory bowel disease, and other chronic inflammatory arthritides/connective tissue diseases.
• Chronic infection, including HIV, tuberculosis, chronic osteomyelitis, and infective endocarditis.
• Malignancy.
• Chronic kidney disease (with an additional, separate contribution from reduced erythropoietin production).
• Longer duration and higher activity of the underlying inflammatory condition.

Differentiating iron deficiency anemia from anemia of chronic disease

Ferritin is an acute-phase reactant — its level rises with inflammation, infection, or tissue injury independent of iron stores, so a normal or high ferritin does not exclude iron deficiency once significant inflammation is present. In a patient with active inflammation, a ferritin under 100 mcg/L (rather than the usual under 30 mcg/L cutoff) should raise concern for coexisting iron deficiency; laboratory-specific reference ranges vary and should be interpreted in context.

Interpreting the pattern

• Ferritin is an acute-phase reactant and rises with inflammation independent of iron stores — a normal or high ferritin does not exclude coexisting iron deficiency once significant inflammation is present.
• Transferrin saturation under 20% in the presence of active inflammation and a normal-to-high ferritin suggests functional iron deficiency superimposed on ACD, distinct from isolated ACD (where transferrin saturation is typically low-normal rather than frankly low) and from isolated iron deficiency (where ferritin itself is low).
• C-reactive protein or another inflammatory marker helps confirm active inflammation is genuinely present and supports interpreting an elevated ferritin as inflammation-driven rather than reassuring against iron deficiency.

• Improve hemoglobin and anemia-related symptoms to the extent the underlying disease allows.
• Control or treat the underlying inflammatory, infectious, or malignant condition — this is the primary lever for resolving ACD itself.
• Identify and correct any coexisting absolute or functional iron deficiency, since this component is directly treatable even when the ACD component is not.

• There is no dedicated non-pharmacologic treatment for ACD itself — management is directed at the underlying condition (disease-modifying therapy for inflammatory arthritis, source control/antimicrobials for chronic infection, oncologic treatment for malignancy).
• Dietary iron supplementation is not an effective strategy for isolated ACD, since the underlying hepcidin-mediated block limits absorption regardless of dietary source.

Pregnancy

ACD in pregnancy is managed by treating the underlying condition as in nonpregnant patients, with attention to which disease-modifying therapies are safe in pregnancy for the specific underlying disease. If a coexisting iron-deficiency component requires IV iron, avoid use in the first trimester and confirm current product-specific pregnancy guidance.

Breastfeeding

No ACD-specific restriction; any restriction relates to the underlying disease's treatment, not to ACD itself.

Chronic kidney disease

ACD in CKD has an additional specific contributor — reduced endogenous erythropoietin production — and is the setting where erythropoiesis-stimulating agents are most established; iron sufficiency should be confirmed and maintained before or alongside ESA therapy, since ESAs are ineffective without adequate iron availability.

Monitor hemoglobin alongside markers of the underlying disease's activity — improvement in ACD often tracks with control of the underlying condition rather than following a fixed anemia-specific timeline. If IV iron is given for a coexisting iron-deficiency component, recheck hemoglobin and iron indices at an interval appropriate to the product used, recognizing that ferritin will remain difficult to interpret as long as active inflammation persists.^[2]

1. Confirm the underlying inflammatory/infectious/malignant condition is genuinely as well controlled as achievable — anemia refractory to otherwise-effective disease control should prompt reassessment.
2. Reassess for a coexisting, undertreated iron-deficiency component using transferrin saturation rather than ferritin alone.
3. Reassess for an entirely different or additional cause of anemia (B12/folate deficiency, marrow-suppressive medication effect, hemolysis, occult bleeding) rather than attributing persistent anemia to ACD by default.
4. Consider hematology referral if the anemia remains unexplained or refractory despite the above steps.

• Labelling any anemia in a patient with a chronic disease as ACD without actively excluding iron, B12, and folate deficiency first.
• Giving a trial of oral iron for presumed isolated ACD — it is unlikely to work because of the underlying hepcidin-mediated absorptive block, and a lack of response does not itself confirm the ACD diagnosis.
• Using ferritin alone to exclude coexisting iron deficiency in a patient with active inflammation — use transferrin saturation and the inflammation-adjusted ferritin threshold instead.
• Attributing worsening anemia automatically to worsening of the known underlying disease without checking for a new, separate cause.

How to use this table: ACD itself has no dedicated drug therapy — the table below covers only the IV iron products relevant to the coexisting functional/absolute iron-deficiency component. Treatment of the underlying inflammatory, infectious, or malignant driver is disease-specific and covered in that condition's own guideline, not repeated here. Select any drug name to open its complete Pharmasist Drug Database page.

IV iron for coexisting functional/absolute iron deficiency

Reserved for transferrin saturation under 20% despite a normal/high ferritin in the presence of active inflammation. IV iron bypasses the hepcidin-mediated block that limits oral iron absorption in this setting. Rare but serious hypersensitivity reactions, including anaphylaxis, can occur — administer where resuscitation equipment and trained personnel are immediately available.

Note on erythropoiesis-stimulating agents: epoetin alfa and darbepoetin alfa have an established role in specific ACD subtypes (chronic kidney disease, chemotherapy-induced anemia, low-risk myelodysplastic syndrome, HIV/antiretroviral-related anemia, chronic hepatitis C on ribavirin), but dosing, target hemoglobin, and monitoring depend on the specific underlying condition and are intentionally not duplicated in this chapter.

Evidence note: Content reflects current understanding of anemia of inflammation pathophysiology and management.^[1][2]