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Hereditary spherocytosis
- 1. Hereditary Spherocytosis Dr. Umme Habiba MBBS, M. Phil, CHPE FCPS. Hematology PGR
- 2. Learning Objectives • Describe mode of inheritance of hereditary spherocytosis • Describe pathogenesis of hereditary spherocytosis • Describe morphological features and lab diagnosis of hereditary spherocytosis
- 4. Normal Red Cell Destruction • RBC completes 120 days of life span • Changes in cell membrane occurs Enzyme activity declines • Effected cells less deformable than normal • Recognized by macrophages • Phagocytosis and cell death
- 5. Composition of Red Cell membrane • The red cell membrane consists of: • Proteins: 50% • Lipids :40% • Carbohydrates: 10%
- 6. Functions Of Red Cell Membrane • Erythrocyte membrane that is normal in structure and function is essential to survival of red cell • Maintains stability and normal discoid shape of cell • Preserve cell deformability • Retain selective permeability
- 7. Structure of RBC membrane
- 8. Hereditary Spherocytosis • A genetically determined hemolytic anemia characterized by spherical shaped RBC • Characteristic appearance, round cells with smaller diameter and less flexible • Lack of area of central pallor • Decrease surface to volume ratio • Due to genetic defect in RBC membrane proteins • Ankyrin • Spectrin • Band 3.1 protein
- 10. Epidemiology • Most common inherited membrane disorder o 75% autosomal dominant fashion o 25% Rarely autosomal recessive
- 11. Cytoskeletal defects in HS
- 13. Pathophysiology
- 15. On Examination • Marked anemia • Pallor • Marked splenomegaly • Gall bladder stones
- 16. Diagnosis Complete blood picture: • Hb = 7-14g /dl May fall below 7 in crises Red cell indices • MCV =N or slightly reduced • MCH= Normal • MCHC= Increased • Plt = normal or decreased
- 17. Peripheral smear • Spherocyte • Polychromatic cells • Target cells • Nucleated RBC can be present severe cases • Plt decreased if splenomegaly • Retic Usually 5-20% even low to 50-70%
- 18. Spherocytosis in peripheral smear
- 19. Routine chemistry testing • Bilirubin: Increased • Indirect bilirubin • Urine urobilinogen: increased • Methaemalbumin: Increased • LDH: Increased • Haptoglobin: Decreased
- 20. Osmotic fragility test • Principle • When an erythrocyte is placed in a hypotonic sodium chloride-(NaCl) solution, a net influx of solvent (water) into the cell-will occur and the cell will swell • If the cell size reaches a certain point, the cell membrane will become leaky and hemoglobin will diffuse out (hemolysis) • If the NaCl solutions hypotonic enough, the cell will rupture • The degree of hemolysis can be measured by determining the absorbance of the supernatant using a spectrophotometer • Confirmation on protein studies
- 22. Summary • Genetic disorder of red cell membrane • Mainly due to ankirin deficiency • Extravascular hemolysis • Severity depend on mutation in gene • Diagnosis on routine lab investigations, osmotic fragility test and protein studies
Editor's Notes
- INTERACTIONS OF RBC MEMBRANE PROTEIN AND LIPIDS:VERTICAL INTERACTIONS Perpendicular to cell membrane . Includes interactions between skeletal lattice on cytoplasmic side to integral proteins and lipids of membrane It stabilizes lipid bilayer defects lead to uncoupling of lipid bilayer from underlying skeleton thus selective loss lipid layer microvesicle formed Proteins include: Ankirin, Band 3 ,Glycoporin and Protein 4.2 etc HORIZONTAL interactions:Parallel to plane of cell membrane includes spectrin head to head attachments and protein interaction at junction complexes Disruption in these interactions lead to destabilization of membrane poikilocyte e.g. Spectrin Actin