Pathology: Hematopathology: Disorders Of Red Blood Cells 2

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This disease is characterized by only one functional alpha hemoglobin gene and marked decrease in the synthesis of alpha chains

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Hemoglobin H disease

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Formed by tetramers of excess beta globin, this has a high oxygen affinity and isn't useful for oxygen exchange- anemia is disproportionate to the level of hemoglobin

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HbH

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This disease occurs mainly in Asians, has symptoms caused by accumulation of excess beta globin, causes extravascular hemolysis, and anemia with splenomegaly:

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HbH Disease

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This condition results from deletion of all 4 alpha hemoglobin chains and leads to intrauterine fetal death

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Hydrops Fetalis

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What causes most of the symptoms seen in hydrops fetalis?

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Excess gamma globin chains forming tetramers which have a high oxygen affinity and cannot deliver oxygen to tissues.

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Tetramers of gamma globin chains:

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Hb Barts

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This condition is caused by a point mutation leading to reduced beta chains or hemoglobin and precipitation of excess alpha chains:

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Beta Thalassemia

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This disease is characterized by hepatospenomegaly, anemia, massive EPO within bone, and secondary hemochromatosis:

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Beta Thalassemia

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Lab results for this condition are high total rbcs, low MCV, and normal RDW.

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Beta Thalassemia

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This condition has a peripheral blood smear with target cells, microcytes, tear drop cells, and nucleated rbcs.

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Beta Thalassemia

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This condition has intravascular hemolysis due to abnormal activation of complement on RBCs because of a deficiency of GPI which anchors CD55 and CD59 to the cell surface:

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Paroxysmal Nocturnal Hemoglobinuria (PNH)

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This condition may cause venous thrombosis of hepatic, portal and cerebral veins secondary to platelet injury and activation:

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Paroxysmal Nocturnal Hemoglobinuria (PNH)

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This condition is caused by a somatic mutation of the PIG-A gene leading to RBCs, platelets and granulocytes deficient in a membrane anchor GPI. Why can it evolve into other stem cell disorders like actue leukemia and aplastic anemia?

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Paroxysmal Nocturnal Hemoglobinuria (PNH) - because it is an acquired clonal disorder of stem cells and can evolve into other stem cell disorders

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A patient presenting with anemia, jaundice and an elevated reticulocyte count is very likely to have what?

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Hemolytic anemia

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What are the two types of hemolytic anemia:

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Intravascular (RBCs destroyed within blood vessels) and Extravascular (RBCs destroyed by spleen, liver and bone marrow)

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What causes most of the effects of hemolytic anemia?

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Excessive catabolism of hemoglobin due to RBC lysis.

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Antibodies bound to RBCs leads to hemolysis:

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Immunohemolytic anemia

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In this type of Immunohemolytic anemia IgG antibodies fix to RBCs at 37C and lead to extravascular hemolysis

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Warm Antibody Type

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IgM antibodies fix complement to RBCs in peripheral cool body parts - as the parts rewarm , IgM is released but C3b remains and leads to extravascular hemolysis

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Cold Agglutinin Type

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This rare form of Immunohemolytic anemia usually seen in children following viral infection, hemolysis may be severe

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Cold hemolysin type

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This occurs when there is narrowing or obstruction of the microvasculature by fibrin formation:

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Microangiopathic hemolytic anemia

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Name three conditions that may cause microangiopathic hemolytic anemia :

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1. DIC
2. Thrombotic Thrombocytopenic Purpura (TTP)
3. Hemolytic Uremic Syndrome (HUS)

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What kind of red blood cells are produced when there is mechanical red blood cell destruction?

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Schistocytes (RBC fragments)

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Name three conditions that cause mechanical RBC destruction:

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Valvular prosthesis, aortic stenosis, aortic coarctation

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is the condition of having a low platelet count of no known cause. Most causes appear to be related to antibodies against platelets. Often it is asymptomatic, however a very low platelet count can lead to visible symptoms, such as purpura (bruises), or more seriously, bleeding diathesis.

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Autoimmune Idiopathic Thrombocytopenic Purpura

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This is a condiiton in which antiplatelet antibodies destroy platelets, it is usually seen in adults, and may be associated with other immune disorders, AIDS, viral infections or drugs.

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Idiopathic Thrombocytopenia Purpura (ITP)

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Clinical pentad of fever, thrombocytopenia, microangiopathic hemolytic anemia, transient neurological deficits, and renal failure.

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TTP

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In chronic ITP, this type of antibodies are seen against platelet membrane receptors GP IIb/IIIa or Ib/IX.

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IgG

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Is a rare disorder of the blood-coagulation system, causing extensive microscopic thromboses to form in small blood vessels throughout the body. Most cases arise from inhibition of the enzyme ADAMTS13, a metalloprotease responsible for cleaving large multimers of von Willebrand factor (vWF) into smaller units. A rarer form, called Upshaw-Schülman syndrome, is genetically inherited as a dysfunction of ADAMTS13. If large vWF multimers persist there is tendency for increased coagulation.

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Thrombotic Thrombocytopenia (TTP)

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Its normal function is to degrade very high molecular weight on von Willebrand multimers and its defect results in TTP

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ADAM-TS 13 metalloprotease

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This condition is characterized by thrombocytopenia with schistocytes in peripheral blood, normal PT and aPTT, and low ADAM-13 level.

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TTP

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Red blood cells passing the microscopic clots are subjected to shear stress which damages their membranes, leading to intravascular hemolysis and schistocyte formation. Reduced blood flow due to thrombosis and cellular injury results in end organ damage. Current therapy is based on support and plasmapheresis to reduce circulating antibodies against ADAMTS13 and replenish blood levels of the enzyme

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Thrombotic Thrombocytopenia (TTP)

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Is a disease characterized by hemolytic anemia, acute renal failure (uremia) and a low platelet count (thrombocytopenia). It predominantly but not exclusively affects children. Most cases are preceded by an episode of diarrhea caused by E. coli, which is acquired as a foodborne illness. It is a medical emergency and carries a 5–10% mortality; of the remainder, the majority recover without major consequences but a small proportion develop chronic kidney disease and become reliant on renal replacement therapy

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Hemolytic-Uremic Syndrome

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This disease is casued by Ecoli strain that causes gastroenteritis in children and the elderly and produces a shiga-like toxin absorbed from inflammed GI mucosa, damaging endothelium. The damage is especially prominent in kidney glomeruli- platelet activation and aggregation leads to thrombi and renal dysfunction.

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Hemolytic-Uremic Syndrome (HUS)

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This disease presents clinically with bloody diarrhea, followed by microangiopathic hemolytic anemia, thrombocytopenia and renal failure.

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HUS

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In these diseases, symptoms are caused by extravascular hemolysis of RBCs containing excess hemoglobin chains, increased iron absorption and bone marrow expansion.

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Thalassemia (alpha and beta)

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This is an acquired disorder of RBC membranes that leads to hemolysis by complement lysis:

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PNH

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This test is instrumental in detecting antibodies and/or complement on patient RBCs:

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The direct Coombs antiglobulin test

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Which three diseases should come to mind in the differential diagnosis of consumptive hematologic processes - all three casue combined microangiopathic hemolytic anemia and thrombocytopenia

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1. DIC
2. TTP
3. HUS