Microcytic red cell changes

• Microcyte

  Cells that are smaller than normal red cells
• Microcytosis

  Red cells that have a MCV less than the lower normal limit (< 76fl in adults)
• Microcytic anaemias

  • Linked by morphologic and pathogenetic features of deficient Hb synthesis
  • Often associated with iron deficiency or impaired iron utilization
  • Hallmark is microcytosis and hypochromia
  • Degree of microcytosis and hypochromia relate to the severity and duration of underlying disorder
• Components required for Hb synthesis

  • Iron
  • Globin
  • Protoporphyrin
• Pathogenetic classification of microcytic anaemias

  • Disorders of iron metabolism
  • Disorders of globin synthesis
  • Disorders of porphyrin and heme synthesis
• Disorders of iron metabolism

  • Iron deficiency anaemia
  • Anaemia of chronic disorders
  • Atransferrinaemia (AR trait)
  • Rare familial microcytic anaemias
  • Gallium administration
• Iron deficiency pathway

  1. Reduced transferrin iron

  2. Reduced Hb production

  3. Microcytic hypochromic cells
• Disorders of globin synthesis

  • Thalassaemias
  • Unstable haemoglobin diseases
  • Hb E disease, Hb E trait
  • Hb C disease
• Thalassaemias

  Group of inherited disorders in which synthesis of one of the normal polypeptide chains of globin is deficient
• Unstable Hb disease

  Abnormal Hb precipitates (Heinz body) and is removed by spleen leading to pronounced hypochromia
• Disorders of heme synthesis and porphyrin

  • Sideroblastic anaemias
  • Defective ALA synthesis (e.g.Vit B6 deficiency/abnormal metabolism, drugs, toxins)
  • Lead poisoning
  • Some haematological conditions
  • Deficiency of heme synthetase
  • Deficiency of coproporphyrinogen oxidase
  • Unknown causes
• Sideroblastic anaemias

  • Characterized by ringed sideroblasts in bone marrow
  • RS are developing normoblasts with pathologic iron deposition (in mitochondria) around nucleus
  • May be inherited or acquired
• Laboratory evaluation of microcytic disorders

  • Tests to detect and define a microcytic anaemia
  • Tests to distinguish between the 3 major disorders: iron deficiency, anaemia of chronic disorder, thalassaemia
• Tests to detect and define a microcytic anaemia

  • Full blood counts
  • Blood film
  • Biochemical features
  • Bone marrow examination
• Full blood counts

  • Reduction in Hb, Hct/PCV, RBC no.
  • Reduction in MCV, MCH, MCHC, WBC, Plts (Variable)
• Blood film

  • Red cell morphology - microcytes, hypochromia, anisocytosis, poikilocytosis
  • WBC, Plt morphology normal
• Biochemical features

  • Serum iron
  • Serum ferritin
  • Transferrin saturation
  • Total iron binding capacity (TIBC)
  • Serum Transferrin receptors
  • Erythrocyte (zinc) protoporphyrin
• Bone marrow examination

  • Absent iron stores in bone marrow in iron deficiency(Perl's stain/Prussian blue reaction)
  • Sideroblastic anaemia - see sideroblasts
• Perl's stain

  • Reduced iron stores
  • Increased iron stores
  • Normal iron stores
• Tests for abnormal haemoglobin/globin chain

  • Hb electrophoresis
  • HPLC
  • Globin synthesis studies
  • Others
• Further tests to determine cause

  • For cause of iron deficiency
  • Genetic studies
  • Lead levels
  • For chronic disorder
• Microcytic "TAILS"

  • T = Thalassemia
  • A = Anemia of chronic disease
  • I = Iron Deficiency
  • L = Lead Poisoning
  • S = Sideroblastic