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MLAB 1415-Hematology Keri Brophy-Martinez Chapter 14: Introduction to Hemolytic Anemias Hemolytic anemia • Anemia caused by hemolysis of red blood cells – Hemolysis is the destruction of erythrocytes resulting in the release of hemoglobin • Results in reduction of normal red cell lifespan. • Normocytic, normochromic anemia • RBC’s are prematurely destroyed Classified by… • Source of defect causing the hemolysis – Intrinsic/extrinsic • Poikilocyte present – Schistocytes/Spherocytes • Mode of onset – Inherited/acquired • Location of hemolysis – Intravascular/Extravascular Lab Features • Reticulocytosis – RPI> 2 • Erythroid hyperplasia of bone marrow • M:E ratio decreased • Peripheral blood – Normochromic,normocytic – Polychromasia – nRBCs • Tests for heme catabolism abnormal – Unconjugated/conjugated bilirubin – Haptoglobin Lab Features Increased Bone Marrow Production of Erythrocytes Increased Erythrocyte Destruction Reticulocytosis (RPI>2) Anemia Leukocytosis Spherocytes, Schistocytes, Poikilocytes nRBCs in PB Decreased haptoglobin Polychromasia Increased bilirubin Normoblastic erythroid hyperplasia in bone marrow Increased LDH M:E decreased Increased urobilinogen Increased expired CO Hemoglobinemia* Hemoglobinuria* Hemosiderinuria* *Only with intravascular hemolysis Diagnostic Approach to Hemolytic Anemias Increased RBC Production Increased RBC Destruction COOMBS (DAT) test Peripheral blood smear RBC Morphology Immune Hemolytic Anemias Lab Investigation Definitive Diagnosis Clinical Findings • • • • • • • Jaundice Pallor Fatigue Cardiac symptoms Gallstones Dark or red urine Splenomegaly Sites of Destruction • Intravascular – Hemolysis occurs within the circulation – RBC’s are severely damaged • Extravascular – Hemolysis occurs within the macrophages of the spleen, liver or bone marrow – More common than intravascular Intravascular Destruction 1. 2. 3. RBC is hemolyzed Free hgb released into plasma Hgb binds to haptoglobin – If haptoglobin depleted, hemopexin can step in 4. This complex goes to liver 5. Complex converted to bilirubin 6. Bilirubin excreted to intestinal tract Terms 1. Hemoglobinemia – Occurs if hemopexin and haptoglobin is depleted. Free hgb circulates in blood. 2. Hemoglobinuria – Occurs if free hgb can not be absorbed by the liver and kidney 3. Hemosiderinuria • Hemosiderin in the urine, sign of filtration of hemoglobin thru the kidney Causes of Intravascular Hemolysis Activation of Complement on RBC Membrane Physical or Mechanical Trauma to the RBC Toxic Microenvironment of the RBC Paroxysmal noctural hemoglobinuria Microangiopathic hemolytic anemia Bacterial infections Paroxysmal cold hemoglobinuria Abnormalities of heart vessels Plasmodium falciparum infection Some transfusion reactions Disseminated intravascular coagulation Venoms Some autoimmune hemolytic anemias Thermal injury Acute drug reaction in G6PD deficiency Extravascular Destruction 1. Hgb is degraded within the phagocyte to heme and globin a. Phagocyte locations: • Spleen: removes slightly damaged RBCs • • Liver: removes severely damaged RBCs Bone marrow: remove mature precursor cells that are intrinsically abnormal 2. Heme further degraded to iron, biliverdin and carbon monoxide 3. Biliverdin enters plasma as bilirubin 4. Bilirubin binds to albumin, excreted by the liver Causes of Extravascular Hemolysis Origin Anemias Inherited RBC Defects Thalassemia, Hemoglobinopathies, Enzyme deficiencies, Membrane disorder Acquired RBC Defects Megaloblastic anemia, Vitamin E deficiency in newborns Immunohemolytic anemias Autoimmune, Drug induced, Some transfusion reactions Source of Defect of RBC • Intrinsic – Abnormality of the RBC • Membrane • Cell enzymes • Hemoglobin molecule – Usually hereditary • EXCEPTION: Acquired – Paroxysymal noctural hemoglobinuria (PNH) – Site of hemolysis: extravascular Source of Defect of RBC • Extrinsic – Antagonist in cell’s environment causes injury to the RBC • Antagonistic plasma factors • Traumatic physical cell injury • Immune mediated cell destruction – RBC is normal – Usually acquired – Site of hemolysis: intra or extravascular Referenes • Harmening, D. M. (2009). Clinical Hematology and Fundamentals of hemostasis (5th ed.). Philadelphia, PA: F.A. Davis Company. • McKenzie, S. B. (2010). Clinical Laboratory Hematology (2nd ed.). Upper Saddle River, NJ: Pearson Education, Inc..