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ABNORMALITIES OF ERYTHROCYTE MEMBRANE

ABNORMALITIES OF ERYTHROCYTE MEMBRANE. Hereditary Spherocytosis. Shape change is the fundamental defect – abnormality in the cytoskeleton of the red cell membrane. HEREDITARY SPHEROCYTOSIS. Intrinsic erythrocyte membrane defect Occurrence 1 in 5000

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ABNORMALITIES OF ERYTHROCYTE MEMBRANE

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  1. ABNORMALITIES OF ERYTHROCYTE MEMBRANE

  2. Hereditary Spherocytosis Shape change is the fundamental defect – abnormality in the cytoskeleton of the red cell membrane

  3. HEREDITARY SPHEROCYTOSIS • Intrinsic erythrocyte membrane defect • Occurrence 1 in 5000 • Most common in those of Northern European descent • 75% autosomal dominant, remaining AR • Abnormal permeability to sodium, RBCs are less deformable • Chronic extravascular hemolysis • Splenectomy corrects hemolytic process

  4. RBC MEMBRANE • Proteins & lipids • Normal discoid shape • Preserves cell deformability • Selective permeability

  5. Pathophysiology & Consequence

  6. LABORATORY FINDINGS • Hemoglobin normal/decreased • Blood smear – spherocytes • MCV - ↓, MCHC - ↑ • Increase in reticulocytes • Nucleated red cells • Bone marrow- normoblastic erythroid hyperplasia • Biochemical findings - ↑Unconjugated bilirubin, LDH, fecal & urine urobilinogen

  7. Osmotic fragility test • Measures erythrocyte’s resistance to hemolysis by osmotic stress • RBCs are incubated in hypotonic solution of NaCl of varying concentrations • As NaCl concentration decreases, the RBCs take in water to achieve osmotic equilibrium. The cell swells and finally hemolysis occurs .

  8. Normal cells begin to hemolyse at NaCl concn of 0.5% and completes at 0.3% • Spherocytes are incapable of expanding so much, so very little fluid is required before the cells hemolyse • So in HS hemolysis starts early and is completed between 0.5% - 0.4% - Increased Osmotic Fragility • In mild HS – incubate blood at 37 degrees for 24 hrs

  9. HEMOLYTIC ANEMIAMembrane abnormalities - Enzymopathies • Deficiencies in Hexose Monophosphate Shunt • Glucose 6-Phosphate Dehydrogenase Deficiency • Deficiencies in the EM Pathway • Pyruvate Kinase Deficiency

  10. Glucose 6-Phosphate DehydrogenaseFunctions • Regenerates NADPH, allowing regeneration of glutathione • Protects against oxidative stress • Lack of G6PD leads to hemolysis during oxidative stress • Infection • Medications • Fava beans • Oxidative stress leads to Heinz body formation,  extravascular hemolysis

  11. 5 types Protection against prevalance of Malaria CLINICAL PRESENTATION- Acute haemolytic anaemia Chronic--- Neonatal hyperbilirubinemia Favism

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