Hemolytic Anemia

Question 1

Hemolytic Anemia Classification System

Answer 1

Extravascular: within macrophages in spleen, liver, and bone marrow; this is how RBCs die normally
Intravascular: within the blood stream and leave substances that are not supposed to be in the blood; abnormal

Intrinsic: RBC issues stem from hereditary causes such as abnormal Hb, enzyme defects, membrane abnormalities
Extrinsic: RBC issues stem from outside processes such as immunologic, mechanical factors, infections/toxins, liver disease, and hypersplenism

Question 2

Mechanisms of Extravascular Hemolysis

Answer 2

Abnormal environment: infections, medication, immunologic process
RBC membrane abnormalities
RBC metabolic defects
Abnormalities in Hb structrure

Question 3

Mechanisms of Intravascular Hemolysis

Answer 3

1. mechanical damage to RBCs:
   a. fibrin present in vessel lumen (DIC or vasculitis)
   b. physical trauma of RBCs (prosthetic valves)
   c. thermal injury from burns
2. Infection (malaria) or toxins (poisonous snakes)
3. complement mediated: cold agglutinins, incompatible RBCs transfusions, paroxysmal nocturnal hemoglobinuria

Question 4

Pathogenesis of Intravascular Hemolysis

Answer 4

Hb released binds to haptoglobin to decrease serum level of haptoglobin, but when binding capacity is exceeded the free Hb is filtered in the kidneys, thus turning the urine red

Hb can be detected in tubular cells and can be microscopically, but cannot see RBCs
Hemosiderin can be seen in the urine because product from Hb = positive for iron stains of urinary sediment

Question 5

Intrinsic - Hereditary RBC Disorders

Answer 5

Abnormal Hb: sickle cell disease and thalassaemias

Membrane abnormalities: spherocytosis, elliptocytosis

Enzyme defects: G-6-PD

Question 6

Extrinsic - Acquired Hemolytic States

Answer 6

Autoimmune hemolytic anemia
Malaria
Microangiopathic hemolytic anemia

Question 7

Hemolytic Anemia: Labs

Answer 7

CBC
Reticulocyte count (increases)
Erythropoietin
Peripheral smears (increased RBC fragments)
Bone marrow aspirate and biopsy

Question 8

Intravascular Hemolysis: Labs

Answer 8

decreased serum haptoglobin level
\+ Free Hb in plasma  
\+ Hemoglobinuria
\+ iron stain in urinary sediment
Presence of plasma or urine hemoglobin
Detection of hemosiderin in renal tubular cells in the urinary sediment

Question 9

Extravascular Hemolysis: Labs

Answer 9

Coombs test: Igs and Complement on RBC surface

Hb electrophoresis for hemoglobinopathies

These tests detect Hb and complement (Ab) in RBC surfaces or Hb electrophoresis

Question 10

Peripheral Smear Findings

Answer 10

RBC morphological abnormalities: sickle cells, bite cells, schistocytes, spherocytes.

RBCs agglutination (increased Ig, parasites)

Erythrophagocytosis

Polychromasia- increased number of RBCs

Bone Marrow: hyperplasia of erythroid progenitors

Question 11

Hemolytic Anemia: Dx

Answer 11

Compensatory production 
Reticulocyte index > 3 
Absolute count is > 100,000/ mm3
Indirect bilirubin is elevated
LDH may be elevated
Serum haptoglobin diminished

Intravascular 
	Urine and plasma Hb
	Iron stains of urinary sediment
Extravascular
	Coombs tests
	Hb electrophoresis

Question 12

Hereditary Spherocytosis

Answer 12

Autosomal inherited disorder
Intrinsic defects in RBCs membrane: spheroid RBCs (less deformable), which cause destruction especially in spleen
1/5000 in northern Europe
Reduced membrane stability
Beneficial effect of splenectomy (treatment)

Question 13

Hereditary Spherocytosis Protein Defects

Answer 13

Defects in the RBC cytoskeleton that cause the cell to assume a spherical shape caused by a defect in the expression of spectrin, ankyrin, band 3, and protein 4.2

Question 14

Hereditary Spherocytosis: Symptoms and Histology

Answer 14

Distinctive: Spherocytes, small and hyperchromic (lack central paleness).
Reticulocytosis
B.M. erythroid hyperplasia
Hemosiderosis
Mild jaundice
Cholelithiasis in 50% of the affected adults
Moderate splenomegaly (erythrophagocytosis)

Question 15

Osmotic Fragility Test

Answer 15

Get RBCs from venipuncture and expose to different concentrations of sodium chloride from 0-1%
The volume to area ratio is higher in spherocytosis
Fragility is increased in these cells because in normal RBCs in 1%, which is the normal concentration of NaCl in the blood, so at 0.5% it will lyse, but as concentrations become closer to 1% (normal in body) then the cells will be less likely to lyse. In spherocytosis cells, the cells are more fragile and so they lyse between 1% and 0.5% because they cannot handle the concentration difference as much, so they lyse sooner than 0.5%

Question 16

Herediary Spherocytosis - Diagnosis

Answer 16

Osmotic fragility test- initial

Molecular studies of ankyrin gene - confirms dx

Question 17

G6PD

Answer 17

Impaired enzyme function reduce the ability of RBCs to protect against oxidative stress/injury causing acute episodic intra/extravascular hemolysis
Leads to anemia, hemoglobinemia, hemoglobinuria
Lysis is self limited
Prevalent in areas where malaria is endemic
Increases Hb presence in blood and urine

Hb oxidation causes denaturation in globin chains, which precipitate in the cytoplasm creating Heinz bodies and induces hemolysis

Presence of Howell-Jolly bodies, Heinz bodies, and bite cells

Question 18

RBC Extrinsic Defects

Answer 18

Immune hemolytic anemia:RBC covered with Ig and/or C3

Non immune hemolytic anemia:RBC trauma

Question 19

Immune Hemolytic Anemia

Answer 19

Ab and can be classified by warm or cold Ab depending on which temperature the Ab are functional; intra or extravascularly

Lysis occurs at warm temperatures (37/98.9) with IgG involvement, splenic macrophages recognize Fc receptors, but 50% idiopathic

Lysis occurs at cold temperatures (4/39.2) with IgG or IgM involvement, idiopathic or viral (EBV), or Ab against Ag system on RBC

Question 20

The Antiglobin Test

Answer 20

The Antiglobulin test (Coomb’s test) is used to distinguish immune from nonimmune – mediated hemolysis.

The Coomb’s reagent – Antibodies that recognize either the Fc portion of human Ig or C3d

Diagnostic for: 	
hemolytic disease  of the newborn
acquired  autoimmune hemolytic anemia 
transfusion reaction 
RBC sensitization caused by drugs

Positive Test: When blood precipitates because RBC have the Ab on the surface and make net and precipitate

Question 21

Fetal Hemolytic Disorder

Answer 21

Mother becomes sensitive to Ag that are present in fetus, especially with negative Rh factor and the baby has a positive Rh factor and then the mother IgG crosses the placenta and destroys the RBCs of the fetus even within the bone marrow and also destroys hepatocytes which decreases albumin and oncotic pressure and causes edema within the fetus and the fetus cannot survive = hydrops fetalis

Question 22

Hypersplenism Anemia

Answer 22

Anemia secondary to spleen enlargement

Increased RBC sequestration in the spleen/enhanced phagocytosis by macrophages

Causes of hypersplenism: portal hypertension, collagen vascular disease, RA

Blood picture is that of pancytopenia (deficiency of all blood cells including RBCs, WBCs, and platelets)

Question 23

Overall Hemolysis Lab Test Results

Answer 23

LDH – elevated.
Bilirubin – elevated (mostly indirect).
Haptoglobin – decreased.
Peripheral smear – spherocytes, schistocytes bite cells, sickle cells, present.
Reticulocyte count – markedly elevated