🩸 Anemia: Causes, Diagnosis & Management

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 🩸 Anemia: Causes, Diagnosis & Management 

🔹 Definition

Anemia is defined as a reduction in red blood cell (RBC) mass, leading to decreased oxygen-carrying capacity of the blood.
It is usually detected by a low hemoglobin (Hb) or hematocrit (Hct) on complete blood count (CBC).

Group WHO Hb cutoff
Men <13 g/dL
Women (nonpregnant) <12 g/dL
Pregnant women <11 g/dL

🔹 Pathophysiology

Anemia results from one or more of the following mechanisms:

  1. Decreased RBC production (e.g., iron deficiency, bone marrow failure)

  2. Increased RBC destruction (hemolysis)

  3. Blood loss (acute or chronic)

  4. Combined causes (chronic disease, nutritional + inflammatory)

🔹 Clinical Manifestations

System Symptoms & Signs
General Fatigue, weakness, pallor, headache, dizziness
Cardiorespiratory Dyspnea, tachycardia, palpitations, orthostatic hypotension, angina
Neurological (B12 deficiency) Paresthesia, ataxia, confusion, loss of vibration sense
GI (iron deficiency) Glossitis, koilonychia (spoon nails), pica
Hemolytic Jaundice, dark urine, splenomegaly
Severe anemia Syncope, heart failure, shock

🔹 Step-by-Step Diagnostic Approach

Step 1. Confirm anemia

  • ↓ Hb and ↓ Hct on CBC.

  • Compare to normal reference ranges (age, sex, and altitude adjusted).

Step 2. Assess RBC indices

Parameter Interpretation
MCV (Mean Corpuscular Volume) RBC size (micro/normo/macrocytic)
MCH/MCHC Hb content per RBC
RDW (Red Cell Distribution Width) Variation in RBC size (↑ in mixed or evolving anemias)

Step 3. Classify by MCV

MCV Category Type of Anemia Common Causes
<80 fL Microcytic Iron deficiency, thalassemia, anemia of chronic disease (late), sideroblastic anemia, lead poisoning
80–100 fL Normocytic Acute blood loss, hemolysis, anemia of chronic disease (early), aplastic anemia, CKD
>100 fL Macrocytic Vitamin B12 or folate deficiency, alcoholism, liver disease, hypothyroidism, drugs (methotrexate, hydroxyurea), myelodysplasia

Step 4. Check Reticulocyte Count

Retic % Interpretation Likely Cause
↑ (>2%) Bone marrow is responding Blood loss or hemolysis
↓ (<2%) Inadequate marrow response Nutrient deficiency, marrow failure, chronic disease

🔹 Microcytic Anemia (MCV <80 fL)

1. Iron Deficiency Anemia

  • Most common worldwide

  • Causes: chronic blood loss (menorrhagia, GI bleed), poor intake, malabsorption (celiac disease)

  • Labs:

Test Finding
Serum iron ↓
TIBC ↑
Ferritin ↓
Transferrin saturation ↓
RDW ↑

Peripheral smear: microcytosis, hypochromia, anisopoikilocytosis
Treatment: Oral/IV iron, treat cause of blood loss.

2. Thalassemia

  • Genetic defect in α or β globin synthesis

  • Labs:

    • Normal or ↑ ferritin

    • Normal TIBC

    • ↑ HbA₂ (β-thalassemia minor) on electrophoresis
      Smear: target cells, microcytosis disproportionate to degree of anemia.

3. Anemia of Chronic Disease (ACD)

  • Mechanism: ↑ hepcidin → ↓ iron release & ↓ EPO response

  • Labs:

Test ACD
Serum iron ↓
Ferritin ↑
TIBC ↓

Treatment: manage underlying disease; consider EPO if renal cause.

4. Sideroblastic Anemia

  • Cause: Defective heme synthesis (B6 deficiency, drugs, MDS, alcohol)

  • Smear: ringed sideroblasts (Prussian blue stain)

  • Labs: ↑ iron, ↑ ferritin, ↓ TIBC

🔹 Normocytic Anemia (MCV 80–100 fL)

1. Acute Blood Loss

  • Normal MCV, ↑ reticulocytes after few days

2. Hemolytic Anemia

  • ↑ LDH, ↑ indirect bilirubin, ↓ haptoglobin

  • Reticulocytosis, splenomegaly, jaundice

  • May be intrinsic (membrane, enzyme, Hb defect) or extrinsic (immune, trauma)

3. Aplastic Anemia

  • Pancytopenia + hypocellular marrow

  • Causes: drugs (chloramphenicol, chemo), radiation, viruses (EBV, parvovirus B19), idiopathic

  • Tx: immunosuppression, HSCT.

4. Anemia of Chronic Disease (early) and CKD

  • ↓ EPO production → ↓ RBCs

  • Tx: EPO-stimulating agents, iron if low stores.

🔹 Macrocytic Anemia (MCV >100 fL)

1. Megaloblastic (DNA synthesis defect)

Cause Mechanism Labs
B12 deficiency Impaired absorption (pernicious anemia, vegan, ileal disease) ↑ homocysteine & ↑ methylmalonic acid
Folate deficiency Malnutrition, alcoholism, pregnancy, methotrexate ↑ homocysteine only

Smear: macro-ovalocytes, hypersegmented neutrophils
Tx: Replace specific vitamin (avoid folate alone in B12 deficiency — risk of neuropathy).

2. Non-Megaloblastic

  • Alcoholism

  • Liver disease

  • Hypothyroidism

  • Myelodysplasia

  • Reticulocytosis
    Smear: macrocytes without hypersegmentation.

🔹 Special Anemia Syndromes

Condition Key Features
G6PD deficiency Hemolysis after oxidant stress, bite cells, Heinz bodies
Sickle Cell Disease HbS polymerization → vaso-occlusion, autosplenectomy
Hereditary spherocytosis Spherocytes, ↑ MCHC, positive osmotic fragility
Paroxysmal Nocturnal Hemoglobinuria Complement-mediated hemolysis, ↓ CD55/CD59
Hemophagocytic syndrome Activated macrophages engulf blood cells → pancytopenia, ↑ ferritin, hepatosplenomegaly

🔹 Emergency & Supportive Management

  1. Stabilize patient:

    • Airway, breathing, circulation

    • O₂, IV fluids, cardiac monitoring

  2. Identify cause of anemia

    • CBC, retic count, iron/B12/folate studies

  3. Blood transfusion

    • Hb ≤7 g/dL (most adults)

    • Hb ≤8 g/dL (heart disease or symptoms)

  4. Treat underlying cause

    • Replace iron, folate, B12

    • Control bleeding

    • Manage chronic disease

  5. Monitor response

    • Reticulocytosis in 5–7 days after effective therapy.

🔹 Key Mnemonics

MCV Classification

“Little Iron Can Make You Pale”
(Low MCV → Iron deficiency, Chronic disease, Microcytosis, Young RBCs, Poikilocytosis)

Megaloblastic vs Non-megaloblastic

Megaloblastic = DNA problem (B12/Folate)
Non-megaloblastic = Metabolic or membrane issue

🧠 Summary Table

Feature Microcytic Normocytic Macrocytic
MCV <80 80–100 >100
Major causes Iron deficiency, Thalassemia, ACD Blood loss, Hemolysis, ACD, CKD B12/Folate deficiency, Alcohol, Liver disease
Retic count ↓ ↑ or ↓ ↓
Smear Hypochromic, microcytic Normal Macro-ovalocytes
Key test Iron studies Retic count, LDH, Bilirubin B12/Folate, MMA, Homocysteine

🔹 Clinical Pearls

  • Hematocrit >55% → consider polycythemia, not anemia.

  • Always rule out combined deficiencies (iron + B12/folate).

  • Ferritin is the most specific early test for iron deficiency.

  • MCV may be misleading in mixed anemia (e.g., IDA + B12).

  • In elderly or chronic disease, anemia may signal malignancy or marrow infiltration.


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