1. MLAB 1415: Hematology Keri 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
Paroxysymal noctural hemoglobinuria

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 RBC morphology 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 RBC morphology Mild anemia Hgb level increased
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 RBC morphology MCV decreased (25-55 fL)
Extreme erythrocyte morphologies
Fragments, elliptocytes, triangulocytes etc

18. Treatment of HPP
Splenectomy

19. Disorders Hereditary Stomatocytosis Syndromes No treatment required
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.