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Lectures > Hemolytic Anemias > Flashcards

Hemolytic Anemias Flashcards

1
Q

Hemolytic anemias

Physiology of RBC loss

A

Hemolytic anemias: Short RBC life span associated with features of accumulation of hemoglobin catabolism due to RBC destruction –> associated with increase in erythropoeisis and reticulocytosis

Physiology of RBC Loss:

  • RBCs normally are made in the marrow and survive for 100-120 days
  • for the first day, RBCs still contain ribosome which can be stained as reticulin in reticulocytes = bluish hue of cytoplasm
  • reticulocyte counts are normally 1%
  • as the body tries to make more blood, the reticulocyte count is even higher
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2
Q

Consequences of RBC Hemolysis

A
  • anemia - pallor, shortness of breath, etc.
  • expansion of the marrow space with skeletal deformity (tower skull)
  • growth retardation
  • funny looking RBCs
  • increased reticulocytes
  • increased bilirubin, uric acid and LDH
  • bilirubin gall stones
  • splenomegaly
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3
Q

First step in making a diagnosis of hemolytic anemia

A

Identify presence of hemolysis

  • hemolytic anemias frequently have RBCs that differ from normal RBC size and shape - see differences on blood smear
  • hematologists look at the shape of RBCs and the shape and color of their inclusions to help determine the cause of hemolysis or other causes of anemia
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4
Q

Peripheral RBC morphology

  • acanthocytes
  • basophilic stippling
  • bite cells
  • burr cells
  • cabot’s ring
  • howell-Jolly bodies
A
  • acanthocytes - liver disease, abetaliproteinemia, postsplenectomy
  • basophilic stippling - lead tox, thalassemia
  • bite cells - G^PD deficiency, oxidant drug hemolysis
  • burr cells - uremia, ulcers, gastric CA
  • cabot’s ring - splenectomy, mebaloblastic, hemolytic
  • howell-Jolly bodies - splenectomy, megaloblastic, hemolytic
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5
Q

Peripheral RBC morphology

  • pappenheimer bodies
  • schistocytes
  • spherocytes
  • stomatocytes
  • target cells
  • teardrop cells
A
  • pappenheimer bodies - sideroblastic anemia, splenectomy
  • schistocytes - microangiopathic hemolytic anemia, prosthetic heart valves, burns
  • spherocytes - hereditary, immune hemolytic anemias
  • stomatocytes - hereditary, immune, membrane expanded by cholesterol
  • target cells - liver dx, spleen out, thalassemia, HbC
  • teardrop cells - myelofibrosis, myelophthesis
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6
Q

Laboratory diagnosis of hemolytic anemia

A
  • low hgb can normochromic normocytic, microcytic hypochromic or macrocytic
  • RBC shape/fragments
  • reticulocyte count
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7
Q

Hemolytic anemia diagnostic features

A
  • reticulocytosis
  • blood smear = might see hypochromic microcytic anemia or may be normal
  • signs of heme degradation
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8
Q

Extravascular vs. intravascular hemolysis

- Lab findings

A

Extravascular: Removal of RBCs by the reticuloendothelial system (spleen macrophages)

  • increased indirect and direct bilirubin
  • increased LDH
  • increased free hgb
  • decreased haptoglobin
  • methemoglobin increased –> a form of catabolized hemoglobin that increases as haptoglobin is depleted because there is no more protein to buffer it
  • bilirubin in the urine
  • hemosiderinuria
  • hemoglobinuria

Intravascular: Destruction of RBCs in the circulation with free hemoglobin release

  • increased direct bilirubin
  • increased LDH
  • decreased haptoglobin
  • bilirubin in the urine - rarely
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9
Q

Second step in diagnosing hemolytic anemia

A

Identify the mechanism of hemolysis

  • intrinsic defect/intracorpuscular
  • extrinsic defect/extracorpuscular –> immune or non-immune mediated
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10
Q

Intrinsic hemolytic anemias

A
  1. Abnormal RBC membrane = spherocytosis, elliptocytosis, paroxysmal noctural hemoglobinuria
  2. Enzyme disorder = G6PD of pyruvate kinase deficiency
  3. Abnormal hemoglobin = sickle cell, thalassemias
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11
Q

Hereditary spherocytosis

A

Defect of the RBC membrane (mutation in the ankyrin protein) that renders the erythrocytes spheroidal and susceptible to splenic sequestration and destruction
- defects in membrane binding to cytoskeleton lead to membrane separation and loss as microvesicles –> small dense micropherocytic RBCs result that have reduced osmotic fragility

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12
Q

Diagnosis and management of spherocytosis

A

Diagnosis:

  • blood smear = anemia, spherocytosis
  • osmotic fragility test
  • bone marrow = increased erythropoeisis
  • clinically = jaundice (increased bilirubin) + splenomegaly

Treatment:

  • folic acid treatment is recomended to prevent aplastic anemia due to the hyperactive bone marrow
  • splenectomy in symptomatic patients
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13
Q

Hereditary elliptocytosis

A

Autosomal dominant inherited defect

- elliptical RBC and variation in RBC shape = poikilocytosis

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14
Q

Paroxysmal nocturnal hemoglobinuria

A
  • RBC membrane defect of DAF (CD55) + membrane inhibitor of lysis (CD59)
  • both factors protect RBCs from complement damage
  • patients have heightened sensitivity of complement because of the loss of DAF
  • a sucrose hemolysis test can be performed to demonstrate heightened sensitivity to complement
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15
Q

G6PD deficiency

A
  • G6PD assessed by submitting RBCs to oxidative stress
  • medications like primaquine will trigger intravascular hemolysis 3 days after taking the drug
  • other triggers of oxidative stress = sulfonamids, nitrofurantoin, fava beans

Mechanism of hemolysis

  • oxidative stress
  • hemoglobin denaturation with precipates called Heinz bodies
  • cause RBC membrane damage and hemolysis with bite cell formation
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16
Q

Pyruvate kinase deficiency

A

Autosomal recessive disorder involving a defect in the energy producing step of the glycolytic pathway

  • results in extravascular hemolysis in the spleen
  • RBC microvesiculation related to low ATP concentrations seen with PK deficiency
17
Q

Non-immune hemolytic anemias

A
  1. Physical trauma
    - prosthetic heart valves = macroangiopathies
    - HUS, TTP, DIC (microangiopathies) –> associated with thrombi in the circulation
    - schistocytes
  2. Infection
  3. Chemical trauma
  4. Other causes
    - hypersplenism = increased phagocytosis –> may need splenectomy
    - liver disease
18
Q

Thrombotic thrombocytopenic purpura

A

Classic diagnosis

  • fever
  • anemia
  • thrombocytopenia
  • renal dysfunction
  • neurologic changes

Modern diagnosis

  • thrombocytopenia
  • schistocytes
  • elevated LDH
  • altered vWF in circulation

Management: Plasma infusion and plasma exchange –> plasma exchange is the gold standard
- performed for days/weeks until the patients platelet count increases

19
Q

Infections causing hemolytic anemias

A
  • malaria
  • babesia
  • stretococcus
  • bartonellosis
  • clostridium perfringens
20
Q

Chemicals causing hemolytic anemias

A
  • medications
  • strong oxidants
  • snake venom
  • lead
  • chlorine in hemodialysis fluid
  • chloramine in hemodialysis fluid
  • arsenic
21
Q

Immune mediated hemolytic anemias

A
  1. Transfusion based immunity
    - ABO incompatibility
    - delayed transfusion reactions caused by Rh, Kell, Duffy, Kidd, etc
  2. Hemolytic disease of the newborn
  3. Autoimmune hemolytic anemias
22
Q

Immune mediated hemolytic anemia

A

Results as an antibody attack against antigens present on the RBC surface
- positive Coombs test

Symptoms

  • fever
  • hypotension
  • flank pain
  • hemoglobinuria
  • constriction of chest
23
Q

Acute hemolytic transfusion reactions

A

Most commonly associated with ABO mismatch due to clerical error

Symptoms:
- pain at site of infusion
- chest pain
- flank pain 
- back pain
hypotension
- hemoglobinemia
- hemoglobinuria
- acute renal failure
- DIC/bleeding
24
Q

Acute vs. delayed hemolytic transfusion reactions

A

Acute

  • usually ABO antigen mismatch
  • IgM antibodies
  • intravascular hemolysis +/- complement anaphylatoxins leading to shock

Delayed

  • minor antigens
  • IgG antibodies
  • extravascular hemolysis
25
Q

Alloimmune vs. autoimmune hemolytic anemia

A

Alloimmune hemolytic anemia = due to allo antibodies –> induced by transfusion or pregnancy

Autoimmune hemolytic anemia = due to autoantibodies –> inappropriate immune response

26
Q

Warm vs. cold autoimmune hemolytic anemia

A

Warm - at 37 C

  • extravascular hemolysis –> phagocytosis in the spleen
  • IgG mediated
  • drug induced –> methyl-dopa, penicillin, quinidine and salicylates

Cold - below 30 C

  • intravascular –> complement mediated
  • IgM mediated
  • associated with infections = mycoplasma pneumoniae –> antibody directed against I-antigen
  • cold agglutinin disease and Raynaud’s phenomenon
27
Q

Paroxysmal cold hemoglobinuria

A

IgG antibody directed against P-RBC antigen

- binding complement –> intravascular hemolysis at 37 C

28
Q

Hemolytic disease of the newborn

A

Mother exposed to fetal RBC antigens which she lacks and to which she forms a humoral immune response (other than ABO) antigen
- maternal IgG antibodies cross the placenta and hemolyze fetal RBCs

Symptoms

  • elevated bilirubin
  • fetal anemia
  • fetal compensatory extramedullary hematopoiesis

Lectures (46 decks)

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