Blood And Lymph- Hemolytic Anemia By Turnicky

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Blood and Lymph- Hemolytic Anemia by Turnicky

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Blood and Lymph- Hemolytic Anemia by Turnicky

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Accelerated Red Cell Turnover

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Premature removal of circulating red cells due to lysis within the circulatory system (intravascular) or premature removal by the reticuloendothelial system of spleen, liver and BM (extravascular)

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Hemolytic Crisis

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an acute exacerbation of hemolysis due to activation of macrophages usually secondary to viral infection

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Aplastic Crisis

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impairment or cessation of BM red cell production. (parvovirus B19)

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Marrow Exhaustion

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depletion of nutrients, folic acid, or iron

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Intravascular Hemolysis

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-RBC is destroyed within the vessel
-Free Hb is released and bound to haptogloblin
-Transported to the liver and metabolized to bilirubin which is excreted via the bile duct into the bowel
-When transport proteins are depleted free Hb circulates in the plasma (hemoglobinemia) and some is filtered by the kidney (hemoglobinurea)

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Intravascular: mechanism

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Activation of complement
-Complete activation

Physical trauma
-Microangiopathic anemias/DIC
-Artificial heart valves
-Thermal burns
-March hemoglobinemia

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Extravascular Hemolysis

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-Red cell removed by macrophages in spleen, liver and bone marrow
-More common than intra-vascular hemolysis
-No hemoglobinemia or hemoglobinurea

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Extravascular HemolysisMechanism

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-Fab (IgG) portion binds to rbc
-Fc portion is exposed; trapped in red pulp of spleen by macrophage’s Fc receptor.
-Macro pits the membrane, with loss of membrane becoming a spherocyte
-Spherocyte is rigid, trapped in the red pulp and removed.
-IgM/rbc complex is not removed from circulation because macrophage does not have receptors for Fc portion of IgM.
-IgM efficient activator of Complement
-red cell lysed with intravascular hemolysis if complete Complement activation
-Incomplete Complement activation, C3b attached to red cell membrane with extravascular phagocytosis

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What is an intrinsic red cell defect?

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Intrinsic (and abnormality of the red cell itself)

Usually hereditary
-Membrane defect
-Enzyme defect
-An abnormal hemoglobin

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What is an extrinsic red cell defect?

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Extrinsic: The red cell is an innocent bystander to a chemical, mechanical or infectious agent; usually acquired. Hemolysis maybe intra or extravascular.
-Immune mediated
-traumatic injury
-Splenomegally
-Toxic plasma factor (venom, infection parasite, drug, or chemical)

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*If you see a particularly high ______, you're probably dealing with hemolytic anemia.

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reticulocytosis.
-Generally >4% (hallmark of accelerated red cell turnover)
-Do corrected Reticulocyte count
-Polychromatophilic cells which are larger and more blue staining than normal red cells
-May produce elevated MCV

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What may you see in a peripheral smear?

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Microspherocytes: Hereditary spherocytosis, Autoimmune hemolytic anemia, Burns/thermal injury, ABO/fetal incompatibility

Target cells: hemoglobinopathies, liver disease, (post splenectomy)

Schistocytes-Cell fragments: Hemolytic –uremic syndrome (HUS), Thrombotic thrombocytopenia purpura (TTP), Disseminated intravascular coagulation (DIC), Prosthetic heart valves

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Autoimmune Hemolytic Anemia

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Autoimmune: immune reaction to self antigens
-Warm- 70%, most common, IgG-mediated, idiopathic mostly
-Cold
-Paroxysmal cold hemoglobinemia

*depending on the thermal activity of the antibody formed

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Warm Autoimmune HA, specificity of Ab is usually directed against the...

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...Rh system (high incidence of Ag, thus transfusion is difficult)

-Normocytic Normochromic anemia with spherocytes, reticulocytosis (polychromasia), and +direct antiglogbulin test (DAT).

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Warm Autoimmune HA: Summary

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Warm:
-IgG
-37 degree thermal amplitude
-IgG or C3b attachment to macrophage receptors
-Extravascular or intravascular hemolysis
-Antibody directed against high incidence antigens eg anti-Rh

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Cold Autoimmune HA: Summary

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Cold AIHA:
-IgM
-<30 thermal activity
-Hemolysis due to binding and activation of C by IgM, with complement components becoming attached to rbc in cold
-Extravascular hemolysis

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Cold Autoimmune HA

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-IgM affixing to the red cell membrane in cool environment, activates C, reactivity <37, as the cell enters warm circulation the Ab dissociates from the cell, but leaves C.
-Less common (16%) than Warm
-Ab usually directed against the “I” Ag (present on all adult cells), but maybe anti- i (present on fetal cells)
-Mycoplasma pneumoniae: anti-I
-Infectious mononucleosis & lymphoproliferative disease: Anti-i

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Red cell agglutination occurs in areas

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that cool to the thermal range of the Antibody (finger,toes, ears) with discoloration, pain, numbness, referred to as acrocyanosis or Raynauld’s phenomenon.

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Paroxysmal Cold Hemoglobinuria

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-Rare, may occur at any age. Previously assoc. with syphilis, now seen in kids after viral infections (measles, mumps)
-Distinct; biphasic IgG Ab, fixes in cold, upon warming activates terminal C components with lysis. Anti P antigen
-Sharp drop in Hb, symptomatic