Section 16 - Anemias Caused by Impaired Production of RBCs

Anemia

A condition in which there is reduced oxygen delivery to the tissues

May result from:

• Increased RBC loss- destruction

• Decreased Production of RBC

Look for:

Schistocytes,

Icteric blood (bilirubin)

Changes in MCHC

Hgb in urine

Increased MCV

Classification of Anemia

1) Morphologically- MCV or MCHC, helpful when looking at CBC results on case studies

2) Pathophysiologically- what is happening to the production of RBC/Hgb

Iron Notes

• 2/3 of total body Iron is found in Hgb

• Our Fe is repeatedly recycled. Very small amount lost. It’s replaced by diet

• Men and women have very different Fe requirements

• Kids require more due to increased growth rates

• Blood loss necessitates greater Fe need

Iron metabolism

• Bioavailability of ingested Fe is 5=17%

• Most dietary Fe is in the Ferric (+3) state → ferrous state (2+) be reductase enzymes like Duodenal Cytochrome B (DCYTB) for optimal absorption

• Fe is carried into the enterocytes of the intestinal lining by Divalent Metal Transporter 1 (DMT1)

• In enterocyte Fe 2+ oxidized to Fe 3+ by Hephaestin

• Enterocytes can either store Fe as Ferritin (apoferritin + Fe 3+) or move into the rest of the body

• As required by the body, Fe is exported by Ferroportin 1 FPN1 across enterocyte membrane

Ferroportin 1 (FPN1)

• Protein that transports Fe across cell membranes

• Carries Iron from Enterocytes, macrophages, and hepatocytes into blood stream

  • Regulated by Hepcidin

***Takes Fe out of enterocytes and puts it into the BLOOD STREAM. Also takes Fe out of macrophages and liver

Removes Fe from

1) Enterocytes

2) Macrophages

3) The liver

Hepcidin

Binds to ferroportin, inactivating it

Increases when body has adequate Fe stores →decreasing Fe absorption and decreasing release from cells

Decreases when Fe stores drop → Increasing release from cells.

****Hepcidin binds to ferroportin and inactives it. If ferroportin is inactive, there is no way for Fe to get out of the cell. When the body has plenty of Fe, The liver increases hepcidin, decreasing Fe absorption and decreasing the release of of Fe from cells****

Hepcidin Regulation

Involves the Hemochromatosis Gene (HFE)

• When there is plenty of iron HFE allows for the production of hepcidin, blocking release of Fe from Storage

• Mutation of HFE causes Hereditary Hemochromatosis

EPO role in Hepcidin regulation

Epo enhances a hormone produced by rubriblasts called ERYTHROFERRONE (ERFE) that suppresses hepcidin

• Allows more Fe to be released

Apoferritin

Fe 3+ is picked up in blood stream by Apoferritin

✅ Apoferritin binds Fe³⁺ to form ferritin.

📌 Apoferritin binds Fe³⁺ to form ferritin, storing iron in cells & preventing toxicity.

🔹 Key Role in Anemia:

Low ferritin = Iron deficiency anemia;

High ferritin = Inflammatory anemia.

🚀 Key Detail:

• Iron is stored in ferritin as Fe³⁺ (ferric form).

• Ferrous iron (Fe²⁺) is oxidized to Fe³⁺ before storage.

Transferrin

✅ Transferrin transports Fe³⁺ in the blood to tissues (BM, LIVER, SPLEEN) for storage or utilization.

📌 Key Role in Anemia:

High transferrin = Iron deficiency anemia; Low transferrin = Anemia of chronic disease.

A carrier molecule plus Fe.

Transferrin Receptor 1 (TFR1)

location on RBCs/Retics that Transferrin enters nRBCs

✅ Transferrin Receptor 1 (TFR1) mediates RBC iron uptake by binding transferrin-bound Fe³⁺.

📌 Key Role in Anemia:

Upregulated in iron deficiency anemia to increase iron intake;

downregulated in iron overload.

As cellular iron levels fall the level of ferris decreases fall and TfRs increase

TfRs and cellular iron levels are INVERSELY PROPORTIONAL

Ferritin

• Forms when Apoferritin binds Fe3+

• Storage form of Iron in Tissues.

• Water soluble- easily mobilized for utilization

• equilibrium exists between intracellular stored ferritin and serum ferritin

  • If serum ferritin is up, Storage ferritin is up AND TFRS FALL

  • If cellular iron levels fall, the levels of ferritin decrease and the TfRs on cells increase

  • Serum and Storage Ferritin are DIRECTLY PROPORTIONAL

HEMOSIDERIN

• Breakdown product of ferritin found primarily in the RES cells of the LIVER, SPLEEN, and BONE MARROW

• Not water soluble

• Less readily available than ferritin

• Forms a precipitate

• Difficult to make usable

Serum Iron

• Measure of transferrin bound iron

• Fluctuates so should not be used without other labs

• Ref Range: Males 65 – 170 μg/dL (usually lower in females)

Serum Iron = Iron bound to transferrin that is in the blood stream.

fluctuates based on diet, very dynamic, so it can’t be examined in solitude

Total Iron Binding Capacity (TIBC)

• Total amount of Fe that can be bound to transferrin in serum or plasma

• Binding capacity is normally one third saturated

• Ref Range:  250-350 μg/dL

• Values increase in IDA and decrease in iron overload

The total amount of Iron that can be bound to transferrin (carrier of iron)

The TIBC values are going to increase in Iron def anemia and decreases in iron overload

Transferrin Saturation

% saturation of transferrin is measured as the max amount of iron that is bound in plasma or serum

% Transferrin Saturation = Serum Iron   X 100%

TIBC

Ref range:  Males: 20-50%         Females:  15-50%

Serum Ferritin

• Directly proportional to amount of iron stored

• Better measure of body storage iron than serum iron and TIBC

• Reference Range = 20 – 300 μg/dL

• Acute phase reactant

Typical Iron Panel

• Serum Iron – Measures the amount of circulating iron bound to transferrin in the blood. It does not directly reflect iron stores in the liver, spleen, or bone marrow. Bone marrow aspiration is typically required for a direct assessment of iron stores.

• TIBC (Total Iron-Binding Capacity) – Measures the blood’s ability to bind iron with transferrin, providing an indirect measure of transferrin levels. Higher TIBC suggests iron deficiency, while lower TIBC suggests inflammation or iron overload.

• Ferritin – A protein that reflects iron storage in the liver, spleen, and bone marrow. Low in iron deficiency, high in inflammation (acute-phase reactant) or iron overload.

Soluble Transferrin Receptors (sTfRs)

• Uncommon Assay

• Inversely proportional to amount of iron in the body

• Increased when cellular stores of iron are depleted.

• They’re not super stable, so they’re easily sloughed off and they go into the blood where they are measured. More helpful in complex cases

Hepcidin levels given Fe stores

• Adequate Fe stores–liver increases production of hepcidin – inactivates ferroportin - decreasing Fe absorption and release from cells

• When Fe stores drop, decreased Hepcidin produced –less inactivation of ferroportin - increasing Fe absorption and release from cells.

• Not widely used.  May be used for complex cases of coexisting conditions of IDA and AOI. More than Serum transferrin receptor

Free Erythrocyte Protoporphyrin (FEP) or Zinc Protoporphyrin (ZPP)

• Basically, the same test

• FEP is the heme without the iron inserted

• ZPP is heme with zinc inserted in place of iron

• Correlated inversely to ferritin levels

Reticulocyte Count and Reticulocyte Corpuscular Hemoglobin (CHr)

• Retic count is a good indicator or RBC production/how BM is responding to anemia

• DECREASED with diminished and ineffective erythropoiesis

• CHr is an early indicator of iron deficient erythropoiesis.

  • Good indicator of Pts response to Fe therapy

Bone Marrow Iron evaluation

• Rarely justified except in possible sideroblastic anemia, myelodysplatic syndrome or other complex cases.

• Usually assessed by serum ferritin but rare cases require BM examination

Iron Deficiency Anemia (IDA)

Basics

• Most common anemia worldwide

• Epidemiology:

  • Male: 2%

  • Female: 5%

• Presentation:

  • Microcytic, Hypochromic RBCs

    • Small cells are a function of poor Hgb production as are Hypochromic cells.

    • One of the main components of Hgb is Fe

Causes of Iron deficiency Anemia

• Increased Demand

  • childhood and pregnancy

• Excess Loss

  • menstruation and chronic bleed

• Decreased Absorption

  • gastrectomy & malabsorption syndromes

• Iron Poor Diet

  • milk babies, elderly, adolescence, and pregnancy

  **Milk babies = strictly a diet of breast milk past ~4 mons old. Very little Iron

  Adolescence bc of poor dietary habits

Iron Deficiency Anemia

Stage 1

• IRON DEPLETION

• Iron stores in bone marrow are decreased to absent

• No decrease in serum Iron

• Patients are asymptomatic

  • Hgb level is normal

  • RDW usually just slightly elevated

Iron Deficiency Anema

Stage 2

IRON DEFICIENT ERYTHROPOIESIS

• Hgb begins to decrease

• Hgb contents of retics (CHr) is decreased

• HCT is near Normal

• Serum Iron decreased

• FEP/ZPP increased

• If anemia is present

  • Normochromic, noromocytic cells

Iron Deficiency Anemia

Labs

“CLASSIC IRON DEFICIENCY ANEMIA”

Examine:

Serum iron- low

Serum Ferritin - low

TIBC- High (function of capacity to carry iron. high because they have low iron and have lots of capacity left)

%saturation- low

sTfRs- High

Hepcidin- Low

Marrow Iron- VERY Low

Siderblasts/cytes- Low

M:E ration- More E, so M:E is going to get lower, but since the Retics are destroyed in BM you’l still have a low Retic count.

ZPP- Increased

Iron Deficiency Anemia

CBC Results

Hgb/HCT- Low

MCV- Decreased → Microcytic/Hypochromic RBCs present

MCHC- Decreased

RDW- Increased →Anisocytosis

Poik- Present → Target and Ovalocytes

Retic Count- Decreased

WBC & PLT- Not relevant

Treatment of IDA

• Correction of primary disease state

• Oral Dietary Supplements

• If absorption is impaired - IV Iron

• Transfusion only in the event of debilitating symptoms or risk of cardiovascular collaspse

• Ideally, Retics begin to rise in 4-5 days

• Hgb Levels begin to rise in ~weeks (Fully ~6months)

***Not tested on Treatment***

Discuss/List and Explain Two General Mechanisms Involved in Anemic States

1. Increased RBC Loss

• Due to hemolysis (RBC destruction) or excessive blood loss.

• Can be immune-mediated (DAT+ hemolysis) or non-immune (mechanical, infection, toxins, etc.).

• Blood loss may be acute (trauma, surgery) or chronic (GI bleed, heavy menstruation).

2. Decreased RBC Production

• Bone marrow failure (aplastic anemia, myelodysplastic syndromes).

• Defective erythropoiesis (iron deficiency, B12/folate deficiency, thalassemia).

• Anemia of Chronic Inflammation (ACI): Hepcidin-mediated iron sequestration leads to iron unavailability for RBC production.

List Four Hematology Parameters Most Helpful in Evaluating Anemia

1. Hemoglobin (Hgb) & Hematocrit (Hct), RBC

• Measures oxygen-carrying capacity of blood.

• Low Hgb/Hct = anemia.

2. Mean Corpuscular Volume 2(MCV), 3MCHC

• Classifies anemia as microcytic (<80 fL), normocytic (80–100 fL), or macrocytic (>100 fL).

3. Reticulocyte Count

• High retic count: Suggests RBC loss (hemolysis, bleeding).

• Low retic count: Suggests decreased RBC production (bone marrow suppression, nutrient deficiency).

NEXT TIER/FOLLOW UP

Serum Ferritin & Iron Studies (TIBC, % Saturation)

• Low ferritin = iron deficiency anemia (IDA).

• High ferritin with low TIBC = anemia of chronic inflammation.

Look at B-12 & Folate in Macrocytic anemias

Anemia

• Reduced oxygen delivery to tissues due to low RBC count, hemoglobin, or both.

• Can result from RBC loss, destruction, or decreased production.

Effective Erythropoiesis

• Normal RBC production in response to erythropoietin (EPO) stimulation.

• Functional bone marrow & adequate iron supply.

• Occurs exclusively in the bone marrow

Ineffective Erythropoiesis

• RBC production occurs but is defective (e.g., thalassemia, megaloblastic anemia, sideroblastic anemia).

• Leads to increased erythroid precursors but decreased mature RBCs.

• Primary site of ineffective erythropoiesis due to intramedullary apoptosis of defective erythroid precursors before they enter circulation.

• Examples:

  • Megaloblastic Anemia (B12/Folate Deficiency) → DNA synthesis defects → large, immature precursors (megaloblasts) die in BM.

  • Thalassemia → Globin chain imbalance → erythroid precursor apoptosis.

  • Sideroblastic Anemia → Iron-loaded precursors (ringed sideroblasts) fail to mature.

  ✔ Effective erythropoiesis is primarily in the bone marrow.
  ✔ Ineffective erythropoiesis occurs mostly in the BM but can involve peripheral destruction.
  ✔ Liver and spleen may contribute in cases of extramedullary hematopoiesis.

What is the Most Common Cause of Iron Deficiency Anemia (IDA)

Dietary/ nutrient deficiency

menstruation necessitates increased requirements they may nt meet through diet

Anemia of Chronic inflammation (ACI)

Chronic Disease

Secondary to another disease state that has an inflammatory and suppressive effect

• Examples:

  • Chronic Infections

  • Autoimmune diseases

  • Infectious mono

  • Malignancy

  • Any cause of chronic inflammation

Proposed Mechanisms of ACI

1) Inability of RBCs to access iron trapped within macrophages

• Mediated by hepcidin (acute phase reactant, increases with Inflammation)

  • Increased Hepcidin inactivates Ferroportin and decreases Fe Absorption and release from cells

Iron isn’t getting out of macrophages due to Hepcidin up regulation

Plenty of Iron, but It’s inaccessible.

2) Ineffective level of erythropoietin (EPO)

• Cytokines reduce the production of EPO and its responsiveness. Fewer RBCs produced and increased Apoptosis

3) Hemolysis

• The inflammatory response overactive the RES (reticuloendothelial system), which may cause damage to RBC membranes and stimulates erythrophagocytosis

Cytokines & Anemia of Chronic Inflammation

Inflammatory stimulus activates monocytes and T- Cells releasing a flood of cytokines which:

1) Inhibits EPO release

2) Decreased EPO inhibits erythroid proliferation

3) Augments hemophagocytosis

4) Increases hepatic synthesis of hepcidin which inhibits iron release form RES. Also inhibits release of recycled iron via ferroportin.

Key Lab Findings of Anemia of Chronic Inflammation (ACI)

1⃣ MCV (Mean Corpuscular Volume): Slightly low to normal (normocytic or mild microcytic).

• Iron is restricted, but not as severely as in iron deficiency anemia (IDA).

2⃣ MCHC (Mean Corpuscular Hemoglobin Concentration): Decreased.

• Less hemoglobin per RBC due to impaired iron utilization.

3⃣ Serum Iron: Decreased.

• Iron is trapped in macrophages due to hepcidin upregulation.

4⃣ Serum Ferritin: Increased.

• Ferritin reflects iron storage, which remains high despite anemia.

• Also an acute-phase reactant that increases with inflammation.

5⃣ Bone Marrow Iron Stores: Increased.

• Iron is present but inaccessible for RBC production.

6⃣ Sideroblasts (Iron-Stained RBC Precursors in BM): Decreased.

• Decreased because Iron is sequestered in Macrophages

7⃣ TIBC (Total Iron Binding Capacity): Decreased.

• Transferrin is a negative acute-phase reactant, meaning inflammation reduces its levels.

• Less transferrin = less capacity to bind and transport iron.

8⃣ % Transferrin Saturation: Low.

• Serum iron is low, and TIBC is also low, but since iron remains trapped in macrophages, saturation is still low.

9⃣ Hepcidin Levels: Increased.

• Central cause of ACI—hepcidin blocks iron release from macrophages and enterocytes.

10) ZPP (Zinc Protoporphyrin): Increased.

• When iron is unavailable for heme synthesis, zinc replaces iron in protoporphyrin rings.

• Marker of functional iron deficiency.

1⃣1⃣ sTfR (Soluble Transferrin Receptor): Normal.

• Unlike IDA, iron stores are not depleted, so erythroid precursors do not upregulate transferrin receptors.

1⃣2⃣ Bone Marrow M:E Ratio: Increased.

• Myeloid production is unaffected, but erythropoiesis is impaired, increasing the myeloid-to-erythroid (M:E) ratio.

Treatment of ACI

• Treat underlying disease

• Iron Supplements

• EPO stimulating agents

• Transfusion only when patient is clinically unstable

Describe the defect(s) in Sideroblastic Anemia

Defect in heme synthesis resulting in “Iron being left at the alter” (Inadequate Fe utilization in heme synthesis)

1) A Hereditary defect in heme synthesis (rare, X- linked def. in aminolevulinic acid synthase)

2) Autosomal recessive trait- results in Stem cell dysfunction:

• Decreased heme synthesis

• Thrombocytopenia w/abnormal aggregation & prolonged bleeding

• Neutropenia- Increased risk of infection

Acquired Defects in Heme Synthesis associated with Sideroblastic Anemia

Acquired Defects in Heme synthesis

• Primary:

  • Myelodysplastic syndromes

  • Dyserythropoisis/macrocyti

• Secondary:

  • Toxins

  • Lead poisoning - huge red herring. Associated with cognitive impairment

  • Drugs

  • Alcohol

Typical Lab Findings for Sideroblastic Anemia

🔬 Lab Findings:

1⃣ Serum Iron: Normal to Increased – Iron is present but not incorporated into heme.
2⃣ TIBC: Normal to Decreased – No true iron deficiency, iron is not being used properly.
3⃣ Serum Ferritin: Increased – Iron overload from ineffective utilization.
4⃣ sTfRs: Normal to Decreased – Unlike IDA, iron stores are not depleted.
5⃣ FEP (ZPP): Increased – Protoporphyrin accumulates when iron cannot be inserted into heme.
6⃣ Hepcidin: Increased – Iron trapped in mitochondria, but not macrophages like ACI.

Sideroblastic Bone Marrow Findings

🔬 Bone Marrow Findings:

✅ Erythroid Hyperplasia – Ineffective erythropoiesis.
✅ Ringed Sideroblasts (Prussian Blue Stain) – Iron trapped in mitochondria forms a perinuclear ring.
✅ Possible Myeloid/Megakaryocyte Dysplasia – If associated with MDS.

Sideroblastic Anemia Wright Stains/ Peripheral Blood Findings

🩸 Peripheral Blood Smear (Wright Stain):

🔹 Normocytic/Normochromic OR Microcytic/Hypochromic RBCs – Depends on severity.
🔹 Definite Anisocytosis – High RDW.
🔹 Target Cells – Iron dysregulation.
🔹 Basophilic Stippling – Aggregated ribosomes (seen in lead poisoning & some sideroblastic anemias).
🔹 Pappenheimer Bodies – Iron deposits inside RBCs (KEY Clue for Sideroblastic Anemia!).

Lead Poisoning and Sideroblastic Anemia

Interferes with Heme Synthesis in at least 3 ways

Inhibits the conversion of:

1) 5-Amino leveling Acid → Porphobilingen

2) Coproporphyrinogen III → Protoporphyrinogen III

3) Protoporphyrin IX —→ Heme

Define Porphyrias

A Group of rare diseases (usually hereditary) that result in errors heme biosynthesis

Caused by a specific enzymatic defect resulting in an accumulation of a specific porphyrin in tissues

Pathological consequences of porphyrias on RBCs

• Hemolysis: Porphyrin accumulation causes oxidative damage, leading to RBC destruction.

• Ineffective Erythropoiesis: Toxic porphyrins disrupt RBC maturation in the bone marrow.

• Photosensitivity: Light-activated porphyrins damage RBCs and surrounding tissues.

• Iron Overload: Chronic hemolysis leads to excessive iron deposition.

• Anemia: RBC destruction and impaired production result in decreased oxygen transport.

Hemochromatosis

Disorders of Iron Storage

• Results in the inappropriate increase in iron absorption leading to excess iron deposited in tissues

• Doesn’t typically cause Anemia, but does damage organs (liver, hear, pancreas, joints)

Hereditary Hemochromatosis (HH)

• Typically, northern European ancestry (1 in 300 people)

• Excessive iron absorption due to Hepcidin deficiency

• Bronze skin

• Absorb 2-3 times the dietary iron as normal

• Type 1 - most common caused by mutation to HFE gene

  • All 4 types affect Hepcidin, altering regulation of iron absorption

Secondary Hemochromatosis

• Acquired or secondary to other inherited anemias and their treatment

• Result of repeated transfusions which leads to increased iron storage since the body has no mechanism for iron secretion

Hemochromatosis Lab Findings & Treatment

• Erythropoiesis is normal

• Hematologic abnormalities usually not seen

• Increased liver enzymes

• Iron studies – all increased (TIBC usually normal)

• Treatment

  • Therapeutic phlebotomy and / or chelation therapy

MCHC Formula

(Hgb/HCT) x 100 = MCHC

MCV Formula

(HCT x10/RBC) =MCV

Corrected Retic Formula

reticulocyte count (as %) x (HCT/45) = Corrected Retic

RPI formula

• (Corrected Retic/Days to maturation) = RPI

• Days to maturation = 45-HCT = x, (x/2) x 0.1 + 1

• ex: HCT =30, relic -0.9%

• corrected retic = 0.9 s (30/45)=0.667 = 0.6%

• Days to maturation, 45-30 = 15, 15/2=7.5, 7.5×0.1=0.75 +1 = 1.75

• RPI = 0.6/1.75=0.34 → 0.3%