Anemia

Classification

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• Microcytic (MCV < 80 fL): often due to defective hemoglobin synthesis

  • Defective globin chain:
    • Thalassemias
  • Defective heme synthesis:
    • Anemia of chronic disease (late)
    • Iron deficiency (late) ≈ sideroblastic anemia
    • Lead poisoning

• Normocytic (MCV 80-100 fL): categorized by whether there is appropriate bone marrow compensation (high reticulocyte count) or not (low reticulocyte count)

  • Nonhemolytic (low reticulocyte index): Underproduction of RBCs.
    • Iron deficiency (early)
    • Anemia of chronic disease (early)
    • Aplastic anemia
    • Chronic kidney disease
    • Acute blood loss (hemorrhage)
  • Hemolytic (high reticulocyte index): Increased destruction of RBCs.
    • Intrinsic
      • Membrane defects
        • Hereditary spherocytosis
        • Paroxysmal nocturnal hemoglobinuria
      • Enzyme deficiencies
        • G6PD deficiency
        • Pyruvate kinase deficiency
      • Hemoglobinopathies
        • Sickle cell anemia
        • HbC disease
    • Extrinsic
      • Autoimmune
      • Microangiopathic
      • Macroangiopathic
      • Infections

• Macrocytic (MCV > 100 fL)

  • Megaloblastic: Impaired DNA synthesis leads to delayed nuclear maturation relative to the cytoplasm.
    • DNA affected
      • Defective DNA synthesis
        • Folate deficiency
        • Vitamin B12 deficiency
        • Orotic aciduria
      • Defective DNA repair
        • Fanconi anemia
  • Nonmegaloblastic: Macrocytosis without impaired DNA synthesis. Hypersegmented neutrophils are absent.
    • Diamond-Blackfan anemia
    • Liver disease
    • Chronic alcohol overuse

Clinical features

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• Features of hyperdynamic state
  • Bounding pulses
  • Tachycardia/palpitations
  • Flow murmur
  • Pulsatile sound in the ear
  • Possibly heart failure (anemia-induced heart failure)