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MLAB 1415: Hematology Keri Brophy-Martinez

MLAB 1415: Hematology Keri Brophy-Martinez. Chapter 15: Hemolytic Anemia: Membrane Defects. Introduction. Defects due to abnormalities in membrane proteins or lipids Defects alter membrane’s stability, shape, deformability and permeability Hemolysis occurs extravascularly .

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MLAB 1415: Hematology Keri Brophy-Martinez

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  1. MLAB 1415: HematologyKeri Brophy-Martinez Chapter 15: Hemolytic Anemia: Membrane Defects

  2. Introduction • Defects due to abnormalities in membrane proteins or lipids • Defects alter membrane’s stability, shape, deformability and permeability • Hemolysis occurs extravascularly

  3. Overview:Membrane Defects • Skeletal protein abnormalities • Vertical • Separating of lipid bilayer from skeletal lattice • Result in decrease in surface area-to-volume ratio..spherocyte • Horizontal • Disruption of skeletal lattice • Membrane destabilizes • Cell fragmentation..poik • Lipid composition abnormalities • Excess cholesterol accumulates in the outer bilayer of the RBC • Acanthocyte

  4. Conditions Associated with Membrane Defects • Hereditary spherocytosis • Hereditary elliptocytocytosis • Hereditary pyropoikilocytosis • Overhydrated and dehydrated hereditary stomatocytosis • Membrane lipid disorders • Paroxysymalnocturalhemoglobinuria

  5. Disorders • Hereditary spherocytosis (HS) • Defect in ankyrin & spectrin • Results in the formation of fragile spherocytic red cells. • Spherocyte becomes less flexible and more permeable to Na+ • Tends to affect Northern Europeans • Inherited

  6. Clinical Findings • Varies in severity • Compensated hemolytic disease • No anemia • Intermittent jaundice • Splenomegaly • Cholelithiasis: pigment bile stones from increased bilirubin breakdown

  7. Lab Features • CBC • Mild anemia • MCV is usually normal (77-87fL) • MCH normal • MCHC is >36% (This is the only condition in which an MCHC can be truly increased.) • RBC morphology • Spherocyte • Varying degrees of polychromasia, anisocytosis and poikilocytosis

  8. Lab Features • Bone Marrow • Normoblastic erythroid hyperplasia • Increased iron storage • Chemistry • Increased • Bilirubin • Fecal urobilinogen • LD • Decreased • Haptoglobin • Immunohematology • DAT negative

  9. Diagnostic tests for HS • Osmotic fragility - ↑ • Cells are incubated in decreasing concentrations of NaCl. Spherocytes lyse sooner than normal red cells. • Autohemolysis test • Red cells are incubated at 37̊ C for 48 hours. Degree of hemolysis is increased when spherocytes are present. • Red cell membrane studies • Membrane proteins are analyzed using gel electrophoresis.

  10. Treatment of HS • Splenectomy • Corrects for the anemia, but the membrane defect remains

  11. Disorders • Hereditary elliptocytosis • A defect of one of the skeletal proteins • Results in the formation of fragile elliptocytic red cells that are sensitive to mechanical stress. • More permeable to Na+ • Tends to affect blacks, especially in Africa

  12. Clinical findings • Hemolysis not evident • Anemia not characteristic

  13. Lab Features • CBC • Mild anemia • Hgb level increased • RBC morphology • Elliptocytes or ovalocytes

  14. Treatment of HE • Treatment is usually not necessary, but if patients have hemolysis, splenectomy is beneficial.

  15. Disorders • Hereditary pyropoikilocytosis (HPP) • Severe subtype of HE • Deficiency of α-spectrin and a mutant spectrin leads to disruption of skeletal lattice and cell destabilization • Cells fragment when heated • Tends to affect blacks • Presents in infancy or early childhood

  16. Clinical Findings • Hyperbilirubinemia

  17. Lab Features • CBC • MCV decreased (25-55 fL) • RBC morphology • Extreme erythrocyte morphologies • Fragments, elliptocytes, triangulocytes etc

  18. Treatment of HPP • Splenectomy

  19. Disorders • Hereditary Stomatocytosis Syndromes • Overhydrated Hereditary Stomatocytosis (OHS) • Permeable to Na+ and K+, cell takes on water • Cells resemble stomatocytes • Dehydrated Hereditary Stomatocytosis (DHS) • Water content decreased causing cell dehydration so cells look like targets • No treatment required

  20. Lab Features • Anemia is mild to moderate • Increased bilirubin • MCV increased • Stomatocytes: OHS • Target cells: DHS

  21. 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. • http://tiny.cc/d59xy

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