Approach to Anemia in a Young Person & Hemolytic Anemias

AM Report Pearls: RBC-Based Approach to Anemia in Young Person

  •  When you see anemia in a child or young adult, think of the usual causes of anemia but ALSO think of inherited defects according to the location in the red blood cell
    • 1ST LAYER: Membrane defect: e.g. hereditary spherocytosis, hereditary elliptocytosis
    • 2nd LAYER: Hemoglobin defect e.g. sickle cell disease, thalassemias
    • 3rd LAYER: Enzyme defect e.g. G6PD, pyruvate kinase deficiency

AM Report Pearls: Approach to Hemolytic Anemia

  • RBC hemolysis results from damage to the RBC membrane. SEVERE damage leads to intravascularhemolysis. Less severe damage leads extravascular hemolysis.

o   Intravascular hemolysis = RBCs lysed within the vasculature!

o   Causes include:

  • Shearing: MAHAs or defective mechanical heart valves
  • Complement mediated destruction: PNH, some drug reactions, ABO incompatibility, rarelyAIHA from cold agglutins (IgM)
  • RBCs destroyed in the vasculature–>hemoglobinemia–>hemoglobinuria.. NOT seen in extravascular hemolysis. Chronic heme loss in the urine–>concomitant Fe deficiency anemia!

o   Extravascular hemolysis =  RBCs destroyed/phagocytosed by macrophages in the liver, spleen, bone marrow, and lymph nodes

o   Causes include:

  • Immune hemolytic anemia: RBCs coated in IgG, complement, or IgM+complement are phagocytosed in liver, spleen. Partial membrane phagocytosis–>microspherocytes!
  • RBC membrane deformities: poorly deformable RBCs get stuck in sinusoids/cords of Billroth then phagocytosed. Ex: hereditary spherocytosis, G6PD def, thalassemia
  • All components of RBCs are recycled, including Fe, so you don’t get an Fe deficiency anemia

Hemolysis Labs – seen in intra and extravascular hemolysis

  • LDH released from lysed RBCs. Free Hg binds to haptoglobin reducing its serum concentration.

o   Combo of increased LDH  + reduced haptoglobin = 90 percent specific for diagnosing hemolysis

o   Combo of a normal LDH + haptoglobin >25 mg/dL =  92 percent sensitive for ruling out hemolysis

  • Direct Antibody Test(Coombs): for immune mediated hemolytic anemia. Detects IgG or complement on RBCs.

o   In IgM mediated hemolysis, will only detect complement bound to IgM, not the IgM itself!

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