Anemia of Chronic Inflammation

Slide 1 · Anemia of

Chronic Inflammation

Iron sequestration · hepcidin · impaired erythroid response

Pathology lecture

Dr Abu Suraih Sakhri

MBBS, MD (Pathology)

www.abusuraihsakhri.com

Slide 2 · What the learner should explain

Why circulating iron is low even when iron remains stored

How IL-6, hepcidin, and ferroportin determine iron availability

Why erythroid expansion is inadequate for the anemia

How laboratory patterns distinguish inflammation from iron depletion

Slide 3 · Where this anemia fits

Reduced red-cell production

Not primarily accelerated destruction

The disorder among anemias of diminished erythropoiesis.

Both iron supply to precursors and marrow proliferative drive are impaired.

The clinical setting is persistent inflammatory disease.

Slide 4 · Two mechanisms produce the same anemia

Chronic inflammation

Cytokines rise

Restricted usable iron

Hepcidin blocks iron release

Reduced erythroid output

Hemoglobin production limited

Mechanism 1: Iron is retained within storage compartments.

Mechanism 2: Erythropoietin response is inappropriately low.

Both converge on reduced production of circulating red cells.

Slide 5 · Low circulating iron does not always mean depleted iron

Serum compartment

Low serum iron

Storage compartment

Iron retained in macrophages

Vs

This compartmental mismatch is the defining interpretive problem.

The marrow receives insufficient iron despite iron remaining in the body.

Assess iron availability and iron stores separately.

Slide 6 · Three disease families provide the context

Chronic infection

Osteomyelitis · endocarditis · lung abscess

Chronic immune disease

Rheumatoid arthritis · inflammatory bowel disease

Neoplasia

Lung or breast carcinoma · Hodgkin lymphoma

The shared link is sustained inflammation, not a single organ system.

Anemia is a consequence of the underlying disease process.

Slide 7 · Chronic microbial infection

Clinical setting

Persistent osteomyelitis

Serum iron ↓ · ferritin ↑ · TIBC ↓

What connects the infection to diminished erythropoiesis?

Inflammatory mediators increase hepcidin, restricting iron release and availability.

Osteomyelitis is a Robbins example of the infectious category.

The hematologic abnormality may persist with the inflammatory stimulus.

Slide 8 · Chronic immune disorders

Clinical setting

Rheumatoid arthritis with anemia

Systemic inflammation · reduced circulating iron

Why can tissue iron stores be maintained?

Hepcidin-mediated restriction prevents macrophage iron mobilization.

Rheumatoid arthritis and inflammatory bowel disease are textbook examples.

Inflammatory disease activity provides essential diagnostic context.

Slide 9 · Neoplasia-associated inflammation

Clinical setting

Carcinoma of the lung with mild anemia

Ferritin ↑ · serum iron ↓ · TIBC ↓

Which pathological mechanism is plausible?

Inflammation-driven iron sequestration and inadequate EPO stimulation.

The Robbins examples include lung and breast carcinoma and Hodgkin lymphoma.

Do not assume the cancer setting identifies the anemia mechanism by itself.

Slide 10 · Why the clinical setting matters

Inflammatory disease

Context establishes plausible stimulus

Characteristic iron studies

Laboratory pattern supports sequestration

Reduced RBC production

Production defect explains anemia

The diagnosis is a clinicopathologic interpretation.

The same red-cell appearance can arise by other mechanisms.

Morphology without iron studies is not sufficient.

Slide 11 · Follow an atom of iron: Normal cycle

Duodenal absorption

Plasma transferrin

Erythroid marrow

Circulating red cells

Macrophage recycling

Schematic sequence of iron traffic / diagnostic reasoning

Transferrin transports iron to developing erythroid cells.

Senescent red cells return their iron to macrophages.

Macrophages normally return iron to transferrin for reuse.

Slide 12 · Functional iron and storage iron are distinct

Functional compartment

Hemoglobin · myoglobin · enzymes

Storage compartment

Ferritin · hemosiderin

Iron must move between compartments to sustain erythropoiesis.

Storage iron can exist without being readily available to marrow.

Restriction of mobilization is central to inflammatory anemia.

Slide 13 · Ferritin: A reservoir, not a delivery vehicle

Tissue ferritin

Binds and sequesters stored iron

Plasma transferrin

Carries iron to erythroid precursors

Ferritin is especially prominent in hepatocytes and macrophages.

Plasma ferritin generally relates to storage iron in the Robbins description.

The two proteins answer different diagnostic questions.

Slide 14 · Hemosiderin and stainable iron

Ferritin aggregates

Partially degraded in lysosomes

Hemosiderin granules

Visible intracellular stored iron

Prussian blue reaction

Granules stain blue-black

Prussian blue detects storage iron, not adequate delivery to marrow.

Iron staining can therefore remain positive in inflammatory anemia.

This differs from depletion of stainable iron in iron deficiency.

Slide 15 · Transferrin delivers iron to precursors

Plasma transferrin

Iron-bound carrier

Transferrin receptor

Receptor-mediated uptake

Erythroid precursor

Iron incorporated into hemoglobin

Transferrin is synthesized in the liver.

Developing red cells use high-affinity transferrin receptors.

Low circulating iron compromises this delivery route.

Slide 16 · Red-cell recycling is an iron source

Mature erythrocyte

End of circulating life

Tissue macrophage

Hemoglobin iron recovered

Released iron to plasma

Rebinds transferrin

Macrophages in spleen, liver, and marrow recycle red-cell iron.

In inflammation, this major return pathway is restricted.

Recycling failure is functional, not necessarily total iron depletion.

Slide 17 · The enterocyte is another ferroportin gate

Apical uptake

Dietary iron enters duodenal cell

Basolateral release

Ferroportin transfers iron to blood

Iron can be held in enterocyte ferritin instead of exported.

Hepcidin restricts the basolateral export step.

Iron retained in enterocytes can be lost when they slough.

Slide 18 · Hepcidin is the regulatory brake

Liver releases hepcidin

Peptide regulator

Hepcidin binds ferroportin

Membrane iron exporter targeted

Ferroportin degraded

Less iron passes into plasma

Hepcidin controls iron release from enterocytes and macrophages.

High hepcidin lowers accessible iron in the bloodstream.

This regulation is amplified during systemic inflammation.

Slide 19 · Ferroportin is the exit route

Ferroportin active

Iron exits cells to plasma

Ferroportin inhibited

Iron remains intracellular

Vs

Transporter availability determines iron egress.

Hepcidin promotes ferroportin internalization and degradation.

In ACI, reduced export produces iron sequestration.

Slide 20 · High hepcidin limits intestinal transfer

Inflammation

Hepatic response

Higher hepcidin

Enterocyte ferroportin reduced

Less iron reaches blood

Iron retained and shed

Dietary entry into an enterocyte is not equivalent to systemic absorption.

Hepcidin acts at the step exporting iron into plasma.

The gut thus contributes less iron to circulating transferrin.

Slide 21 · High hepcidin traps macrophage iron

Macrophage iron pool

Iron recovered from red cells

Hepcidin–ferroportin action

Exporter inhibited

Reduced iron recycling

Less iron available to marrow

Macrophage sequestration is emphasized.

Storage iron accumulates while serum iron declines.

The marrow cannot readily access this iron reservoir.

Slide 22 · Inflammatory cytokines precede hepcidin rise

Persistent inflammation

Infection · autoimmunity · malignancy

IL-6 signaling

Key inflammatory mediator

Hepatic hepcidin ↑

Circulating iron restriction follows

Interleukin-6 as particularly important.

Hepcidin is produced in the liver.

Cytokine-driven regulation links inflammation to iron metabolism.

Slide 23 · The central IL-6–hepcidin pathway

HEPCIDIN ↑

IL-6 from inflammation

Ferroportin ↓

Macrophage iron retained

Plasma iron ↓

The direction of each relationship matters: IL-6 stimulates hepatic hepcidin.

Hepcidin inhibits ferroportin, rather than directly destroying iron.

The resulting iron shortage is one of availability.

Slide 24 · Why serum iron falls

Iron retained in macrophages

Stored, not exported

Transfer to transferrin ↓

Plasma transport pool receives less

Serum iron ↓

Erythroid precursors receive less

Measured serum iron reflects the circulating compartment.

It does not directly quantify the total amount of iron in the body.

An isolated low serum iron cannot identify the cause of anemia.

Slide 25 · Iron-rich macrophages, iron-poor precursors

Macrophage compartment

Stainable iron preserved / ↑

Marrow precursor compartment

Iron delivery insufficient

Vs

The physiological bottleneck lies between storage and utilization.

Macrophages can contain abundant iron during anemia.

Anemia depends on iron accessible for hemoglobin synthesis.

Slide 26 · Iron-restricted erythropoiesis

Reduced available plasma iron

Low serum iron

Less iron delivered to marrow

Transferrin transport diminished

Hemoglobin synthesis constrained

Erythroid production impaired

This mechanism explains hypochromia when present.

Red cells need iron to synthesize hemoglobin.

The iron-restricted state can exist with increased tissue reserves.

Slide 27 · The “starved amid plenty” paradox

Body iron available in stores

Ferritin and macrophage iron ↑

Iron accessible to erythropoiesis

Transferrin iron ↓

Vs

Iron is redistributed rather than necessarily lost.

Stored iron is biologically unavailable when ferroportin is inhibited.

The compartmental distinction resolves the apparent contradiction.

Slide 28 · Normal erythropoietin compensation

Tissue oxygen delivery ↓

Anemia recognized

Renal EPO response ↑

Kidney drives erythropoiesis

Erythroid proliferation ↑

Marrow increases output

Renal EPO release after anemia-associated hypoxia.

Erythropoietin stimulates committed erythroid progenitors.

ACI interrupts the expected magnitude of compensation.

Slide 29 · Erythropoietin response is inadequate

Expected in anemia

EPO rises sufficiently for stimulus

In chronic inflammation

EPO inappropriately low for anemia

Vs

The comparison is relative to the severity of anemia.

The deficit contributes to poor erythroid progenitor proliferation.

This is independent of the iron-release bottleneck.

Slide 30 · What is known—and what is not—about EPO

Textbook-established

EPO response is inadequate

Proposed explanation

Cytokines may suppress renal EPO

Robbins explicitly identifies uncertainty in the precise mechanism.

Direct inhibition of renal EPO production is suspected.

Do not present the proposed cytokine mechanism as proven.

Slide 31 · Two defects converge in the marrow

Iron delivery ↓

EPO drive ↓

Proliferation and hemoglobinization impaired

Hepcidin and EPO responses affect different parts of erythropoiesis.

Their simultaneous effects account for reduced red-cell output.

The disorder is not explained by a single abnormal iron result.

Slide 32 · Laboratory pattern: The linked findings

Serum iron

LOW

Total iron-binding capacity

LOW

Plasma ferritin

HIGH

Macrophage storage iron

INCREASED

Interpret the pattern as a constellation, not four independent diagnoses.

Low serum iron coexists with high ferritin and preserved stored iron.

This is the characteristic Robbins laboratory profile.

Slide 33 · Serum iron: The circulating pool is restricted

Measured observation

Serum iron ↓

Pathophysiologic explanation

Release from stored pool ↓

Vs

Serum iron is not a direct test of total body iron.

The same low value may occur in iron deficiency.

Storage markers are needed for interpretation.

Slide 34 · Ferritin rises while iron supply falls

Plasma ferritin

Elevated

Plasma iron

Decreased

Vs

Ferritin and serum iron assess biologically different pools.

The divergence supports retention of iron in storage tissue.

High ferritin is part of the textbook ACI profile.

Slide 35 · Total iron-binding capacity is reduced

Total iron-binding capacity

Reduced in ACI

Iron deficiency pattern

Increased in IDA

Vs

Lowered TIBC with chronic inflammation.

In uncomplicated iron deficiency, transferrin/TIBC rises.

The direction of TIBC is useful when serum iron is low in both.

Slide 36 · Marrow macrophage iron discriminates mechanisms

Inflammatory anemia

Storage iron increased

Iron deficiency anemia

Stainable storage iron absent

Vs

The comparison concerns macrophage reserves.

Prussian blue staining reveals marrow storage iron.

Morphological iron assessment complements serum assays.

Slide 37 · Compare the laboratory patterns directly

Measurement

Chronic inflammation

Iron deficiency

Serum iron

Low

Low

Ferritin

Elevated

Low

Total iron-binding capacity

Reduced

Increased

Macrophage iron

Increased

Absent / depleted

The discriminating value comes mainly from ferritin, TIBC, and stores.

Serum iron alone does not separate these disorders.

Slide 38 · Why iron deficiency gives a different ferritin

Iron loss or negative balance

Bleeding · intake · absorption · demand

Storage pool depleted

No iron reserve remains

Plasma ferritin ↓

Serum marker falls

In IDA, insufficient total iron is the primary problem.

In ACI, sufficient stored iron may remain inaccessible.

These contrasting mechanisms predict different ferritin patterns.

Slide 39 · Why TIBC goes in opposite directions

Chronic inflammation

TIBC ↓

Uncomplicated iron deficiency

TIBC ↑

Vs

Both disorders can have low serum iron.

The opposite TIBC directions help interpret the shared finding.

Use the full clinical and laboratory context.

Slide 40 · Prussian blue has a precise question

Marrow aspirate smear

Macrophages examined

Prussian blue stain

Hemosiderin appears blue-black

Storage iron evaluated

Stores present or absent

The stain documents iron storage in macrophages.

It does not measure how effectively transferrin delivers iron.

An image should not substitute for this distinction.

Slide 41 · Red-cell appearance is not uniform

Normocytic

Cell size may remain normal

Normochromic

Hemoglobinization may appear normal

Sometimes mildly microcytic / hypochromic

Iron restriction becomes morphologically apparent

Robbins allows both normal-looking and mildly iron-restricted red cells.

A classic microcytic film is not required to consider ACI.

Slide 42 · Normocytic, normochromic presentation

Cells with usual size and central pallor

Schematic red-cell forms — not a peripheral-blood photograph

Cell size and central pallor may remain within the ordinary pattern.

Low hemoglobin can coexist with relatively unremarkable red-cell morphology.

Context and iron studies remain diagnostic.

Slide 43 · Mild hypochromia and microcytosis

Smaller cells with increased central pallor

Schematic red-cell forms — not a peripheral-blood photograph

Some red cells are smaller and relatively paler.

Reduced iron delivery can restrict hemoglobin synthesis.

This appearance overlaps with iron deficiency anemia.

Slide 44 · Morphology cannot prove iron depletion

Small, pale red cells

Microcytic · hypochromic

Possible interpretations

IDA or chronic inflammation

Vs

The same morphological language applies to more than one mechanism.

Ferritin, TIBC, and macrophage reserves separate the patterns.

Always interpret the smear alongside the clinical setting.

Slide 45 · Integrated diagnostic reasoning

Clinical inflammatory setting

Confirm anemia

Review morphology

Interpret iron studies

Assess stored iron pattern

Schematic sequence of iron traffic / diagnostic reasoning

Start with anemia and a plausible inflammatory condition.

Low serum iron is not the end of the diagnostic process.

The direction of ferritin and TIBC guides differentiation.

Slide 46 · Interpretation: Low iron, high ferritin

Clinical setting

Chronic endocarditis; Anemia on laboratory evaluation

Serum iron ↓ · ferritin ↑

Which iron compartment is likely retaining iron?

Tissue macrophages, under increased hepcidin and restricted ferroportin export.

This pattern favors restricted utilization over complete store exhaustion.

Reduced TIBC strengthens the source-defined profile.

Slide 47 · Interpretation: Low iron, low ferritin

Clinical setting

Anemia with longstanding gastrointestinal blood loss

Serum iron ↓ · ferritin ↓ · TIBC ↑

Which mechanism best explains this constellation?

Depletion of total body iron stores: Iron deficiency anemia.

This is the comparison condition from the preceding Robbins section.

The iron study pattern differs despite a shared low serum iron.

Slide 48 · Clinical severity is usually modest

Anemia itself

Usually mild

Underlying illness

Often dominant symptoms

That the underlying disease drives the presentation.

Anemia-related fatigue may coexist with disease-specific symptoms.

The severity and trajectory should be interpreted clinically.

Slide 49 · The broader symptoms of anemia

Fatigability

Reduced oxygen delivery

Weakness / malaise

Reduced functional reserve

Exertional dyspnea

Increased demand exposes limited delivery

These are general anemia symptoms in the Chapter 14 introduction.

They are not specific to the inflammatory mechanism.

Underlying inflammation may be more clinically prominent.

Slide 50 · Why the body might withhold iron

Inflammation

Iron withheld from plasma

Possible restriction of iron-dependent pathogens

A protective explanation as a hypothesis.

Certain bacteria require iron for pathogenicity.

The host-defense rationale does not eliminate anemia as a consequence.

Slide 51 · Bacteria and competition for iron

Inflammatory response

Host detects disease

Iron sequestered

Plasma iron availability decreases

Some bacteria may be disadvantaged

Iron-dependent growth potentially restricted

H. Influenzae is the specific example given by Robbins.

The proposal is not a universal claim for all pathogens.

The source calls this a best guess rather than a proven purpose.

Slide 52 · Hepcidin and defensins

Hepcidin

Regulates iron availability

Defensins

Innate antimicrobial peptides

A structural relationship between hepcidin and defensins.

This association links iron regulation to innate immunity.

The precise biological relationship remains incompletely understood.

Slide 53 · Therapy addresses the underlying disease

Control chronic inflammatory cause

Infection · immune disease · tumor

Inflammatory stimulus decreases

Pathological iron restriction may resolve

Anemia can correct

Erythropoiesis can recover

Successful treatment of the underlying condition is the reliable corrective strategy identified by Robbins.

The hematologic response is secondary to disease control.

Management should not stop at a laboratory iron value.

Slide 54 · Why iron replacement alone misses the bottleneck

Iron may already be stored

Ferroportin still inhibited

Marrow iron access remains restricted

The textbook mechanism is sequestration, not obligatory iron depletion.

Increasing iron supply alone does not directly reverse hepcidin regulation.

Differentiate true iron deficiency before choosing an explanation.

Slide 55 · Erythropoietin may help selected patients

Mechanistic rationale

Stimulates erythroid progenitors

Clinical scope

Some patients, especially with cancer, may benefit

This addresses the marrow-proliferation component of ACI.

Robbins does not assert that all patients benefit.

No dosing, eligibility threshold, or safety algorithm is specified.

Slide 56 · Case: Infection-associated anemia

Clinical setting

Chronic lung abscess with new anemia

Iron ↓ · ferritin ↑ · TIBC ↓

Which changes are expected in macrophages?

Increased stored iron with restricted release to the plasma pool.

The primary illness and laboratory pattern point to ACI.

The key lesion is impaired mobilization of stored iron.

Slide 57 · Case: Inflammatory bowel disease

Clinical setting

Inflammatory bowel disease with a low hemoglobin

Red cells near normocytic; Iron ↓ · TIBC ↓

What does normal cell size fail to exclude?

Anemia of chronic inflammation; Red cells can remain normocytic and normochromic.

Do not require a microcytic smear for this mechanism.

Ferritin and other iron markers refine the interpretation.

Slide 58 · Case: Carcinoma and low EPO drive

Clinical setting

Breast carcinoma associated with persistent inflammation

Low iron; Marrow production remains inadequate

What mechanism complements iron sequestration?

Erythropoietin is inappropriately low for the degree of anemia.

Cancer-related inflammation is a textbook clinical context.

Reduced EPO stimulation is distinct from reduced iron delivery.

Slide 59 · Case: Iron studies identify depletion

Clinical setting

Chronic blood loss with a microcytic smear

Iron ↓ · ferritin ↓ · TIBC ↑

Why does this not match isolated inflammatory anemia?

Ferritin indicates depleted iron stores and TIBC rises, the reverse of the Robbins ACI profile.

Morphology alone would not discriminate the disorders.

The storage and transport markers point toward iron deficiency.

Slide 60 · Reason through the full causal sequence

IL-6 ↑

Inflammatory signaling

Hepcidin ↑

Hepatic peptide

Ferroportin ↓

Iron exporter downregulated

Iron to marrow ↓

Hemoglobinization restricted

State the direction of every link, not merely the molecules.

The reduced EPO response acts in parallel to this chain.

Ferritin may remain elevated while plasma iron declines.

Slide 61 · High-yield comparison: Two iron states

Feature

ACI

Uncomplicated IDA

Core defect

Unavailable stores

Depleted stores

Serum iron

Low

Low

Ferritin

High

Low

TIBC

Low

High

Marrow macrophage iron

Increased

Absent

The differential hinges on storage versus mobilization.

Morphologic overlap is expected, particularly with microcytosis.

Slide 62 · Explain an apparently paradoxical profile

A patient with rheumatoid arthritis has low serum iron, elevated ferritin, and reduced TIBC. Why is iron delivery to the marrow low?

IL-6 promotes hepatic hepcidin. Hepcidin inhibits ferroportin; Stored macrophage iron cannot reach plasma transferrin efficiently.

The high ferritin does not contradict low serum iron.

Each assay represents a different facet of iron homeostasis.

Slide 63 · The essential diagnostic and mechanistic synthesis

Context: persistent inflammation

Pathway: IL-6 → hepcidin → ferroportin ↓

Outcome: stored iron, poor marrow supply

Laboratory profile: iron ↓ · TIBC ↓ · ferritin ↑

Second hit: inadequate EPO response

The anemia is often mild and subordinate to the underlying disease.

Treating the inflammatory condition is the most reliable corrective approach.