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41 Cards in this Set
- Front
- Back
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What is hematopoiesis?
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A series of events in which pluripotent hematopoietic stem cells from the bone marrow mature into functional blood cells.
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What stimulating factor induces the pluripotent stem cell which has become a trilineage myeloid cell -> erythroid/megakaryocyte to become an erythrocyte?
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BFU-E induced by erythropoetin
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How do we visualize the formed elements in the blood?
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Blood smear
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What drives erythropoiesis (formation of RBC's)?
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Erythropoietin that is triggered by kidneys (and a little bit by the liver) during tissue hypoxia
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What is reticulocytosis?
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Increased number of circulating newly formed red cells identified by residual stainable RNA
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What five structural components form the cytoskeleton of the RBC, allowing for the essential deformability and biconcave shape?
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1.spectrin (alpha and beta)
2. actin 3. ankyrin 4. band 3 transmembrane protein 5. GP transmembrane protein |
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VIP
What is hemoglobin comprised of? |
A heme - 4 pyrrole groups joined into large ring with ferous iron incorporated into the center
Globin chains - 4 chains (in adults 2 alpha and 2 beta) that are arranged in as "knotted sausages". Heme binds to a specific region of the globin chain forming two globin dimers that make up hemoglobin. |
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Describe RBC catabolism:
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Aging RBC's are largely removed from circulation by mononuclear phagocytic engulfment by spleen where heme and globin chains are separated. Heme is divided into iron (recycled) and porphyrin rings (eliminated as bilirubin) and globin is dismantled into amino acids.
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What are the three definitions of anemia?
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Anemia is either:
1. reduction in the oxygen transport capacity of blood 2. reduction below normal in volume of packed cells (hematocrit) 3. reduction in hemoglobin concentration of blood |
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What is the general definition of hemolytic anemias?
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Red cell destruction caused by extrinisic factors or the inability to make a structurally sound RBC.
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VIP
Define this RBC indices: 1. MCV 2. MCH 3. MCHC 4. RDW |
1. Mean cell volume - the average volume of a RBC
2. Mean cell hemoglobin - measures the average mass of hemoglobin per RBC 3. Mean cell hemoglobin concentration 4. Red B C distribution width which measures variations of RBC volume/size (measures anisocytosis) |
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In iron deficiency anemia is there more or less anisocytosis? Beta thalassemia?
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Iron def: more
Beta thal: less |
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Three major characterisitics of hemolytic anemia?
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1. shortening of normal RBC life span (premature destruction of RBC's)
2. accumulation of products of hemoglobin catabolism 3. marked compensatory increase in erythropoiesis with the bone marrow |
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What is hypoxia-inducible factor?
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HIF is a factor that low oxygen levels turns on in the kidney to induce production of erythopoietin via type I interstitial cells
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How does the value of 2,3DPG change in anemia, hypoxia, acidosis, uremia, and cirrhosis of liver?
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In all the cases 2,3DPG increases, causing an increase in affinity for O2 by the hemoglobin
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What is the most important day to day regulator of O2 affinity of hemoglobin?
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2,3 DPG
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VIP
What is the formula for the corrected reticulocyte count? |
Corrected reticulocyte count = %reticulocyte x (Px hematocrit/expected hematocrit)
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What does the value of a corrected reticulocyte count indicate?
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A corrected reticulocyte count of 2% or higher indicates that the Px's anemia is either due to acute blood loss (not chronic as in iron def anemia) or hemolysis. This anemia is hyperproliferative. If the corrected value is less than 2% the anemia is hypoproliferative and the cause of the anemia is in the marrow. We can use absolute reticulocyte count in the same way!
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Compare intravascular hemolysis to extravascular:
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Intravascular - RBC's are destroyed within the vascular compartment resulting in hemoglobinemia, -uria, and hemosiderinuria. Free hemoglobin complexes mostly with haptoglobin (levels usually become low) and is removed by the liver.
Extravascular hemolysis: RBC's are being destroyed by tissue macrophages, just an increase amt of the nL process so no changes in the blood or urine will occur unless there is a problem with the spleen. |
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Hereditary spherocytosis
MCV? |
A Auto dom hemolytic anemia caused by a disorder of the RBC membrane cytoskeleton. Main cause is a spectrin deficiency causing a decreased membrane stability. As the RBC floats through the circulation, bits of it are lost and this forces the RBC to become very small in size with the same amount of substance contained within the cell. The spleen sees all of these small cells and goes to town.
Sympt: anemia, splenomegaly, and jaundice Treatment: splenectomy MCV: very high |
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VIP
G-6 Phosphate dehydrogenase deficiency |
X-linked (men are more suseptable)hemolytic anemia caused by deficiency of G-6-PD which participates in the hexose monophosphate shunt/glutathione pathway. This pathway is put in place to help RBC survive oxidative injury. Glutathione pathway detroys all the injurious oxygen products. In order to keep glutathione up and running NADPH is needed from the hexose monophosphate shunt (which requires G-6-PD). Without it reactive 02 species accumulates and destroys hemoglobin and forms Heinz bodies. As RBC's flow through the spleen Heinz bodies are bitten out of RBC by macrophages forming spherocytes.
Sympt: None until exposed to some oxidative injury (drugs, infection, nL H2O2 formed). |
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VIP
Sickle cell anemia |
A hemolytic anemia caused by a pt mutation on the beta globin chain (valine -> glutamic acid). When the RBC's are deoxygenated HbS (sickle cell hemoglobin) becomes distorted. This distortion is initially reversible with O2 but will eventually become irreversible. This disease not only causes hemolytic anemia but it also can cause occulsion of small blodd vessels. Because this cells are fragile this anemia can be intravascular and extravascular.
Must be homozygous to produce the anemia. |
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Alpha Thalassemia
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A hemolytic anemia due to decreased synthesis of alpha globin chains of hemoglobin A. Most alpha thalassemias are due to deletion of alpha globin gene locus. Theis causes low intracellular hemoglobin and excess of other (beta chain)
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Beta Thalassemia
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A hemolytic anemia caused by the intrinsic abnormality of a point mutation on the gene that encodes the beta globin chain -> synthesis is absent -> inadaquate HbA formation and an excess of alpha chains which form insoluble aggregates which damage cell membranes and make RBC suseptable to phagocytosis
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Compare Thalassemia major to minor:
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Thal major - usually homozygous for beta deficiency. Symptoms involve expanding of the marrow space causing skeletal deformities as well as hepatosplenomegaly. Multiple transfusions are necessary leading to excessive deposition of iron - can cause organ death.
Blood smear = microcytic anemia Thal minor: heterozygotes, few to no symptoms. Must be distinguished from iron deficiency. Blood smear: microcytic hypochromic anemia |
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Why does a "crew cut" appearance of facial bones occur in beta thalassemics?
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In severe beta thal erythropoietin secretion leads to massive erythroid hyperplasia in marrow. This condition erodes existing cortical bone and induces new bone formation giving rise to a "crew cut" appearance on x-rays.
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What is the most severe form of alpha thal?
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Hydrops fetalis - this is caused by a deletion of all 4 alpha globulin genes. This causes excessive delta globin chains which has such a high affinity for O2 that they deliver almost no O2 to tissue.
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What is the only hemolytic anemia caused by an ACQUIRED intrinisic defect in cell membranes?
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Paraoxysmal nocturnal hemoglobinuria
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What do the GPI linked proteins (def in PNH) regulate?
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Complement activity. One GPI linked protein is CD59, a potent inhibitor of C3 convertase, and there by prevents activation of alternative complement pathway. In the absence of GPI-linked proteins = prothrombotic state since complement will be lysing all these cells it shouldn't be.
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Paraoxysmal nocturnal hemoglobinuria
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An unusual acquired membrane defect caused by a mutation in the PIGA gene which is essential for synthesis of the GPI protein - a protein that helps guard cells from lytic activity of complement.
Sympt: EPISODIC intravascular hemolysis (complement activated lysis)that can result in acute leukemia and aplastic anemia. |
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Describe the two types of antibody mediated anemias. What role does the Coombs antiglobin test play?
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Coombs aniglobin test: tests for antibuman antibodies that are bound to RBC's and cause them to aggultinate.
Warm-AB type: (most common) involves IgG AB which are usually idiopathic and induce EXTRAVASCULAR hemolysis (spleen). Cold-AB type: involves IgM autoantibodies and induces INTRAVASCULAR hemolysis (so its complement mediated) |
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How are SCHISTOCYTES formed?
What is MHA? |
In mechanical trauma to RBC's, such as with the prescence of cardiac valve prosthesis and (more commonly) narrowing/obstruction of the vasculature, RBC are damaged by the fibrin deposits found in small vessels. This process is known as Microangiopathic hemolytic anemia (MHA). Fibrin cuts up RBC's forming schistocytes.
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What is an aplastic anemia?
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An anemia caused by a marrow failure induced by suppresion or disappearance of multipotent myeloid stem cells (causes: cancer, medications)
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What are the characterisitics of iron deficient anemia?
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1. serum ferritin is low
2. TIBC is high 3. hemoglobin is low 4. RBCs are microcytic 5. reduced hemoglobin conc - hypochromic |
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Along with iron deficiency, what other anemia is microcytic and hypochromic? Differences?
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Beta thalassemia - here the TIBC would also be low andA2 hemoglobin would be high
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Signs and symptoms of iron deficient anemia?
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fatigue
spoon-shaped nails smooth tongue intestinal malabsorption esphageal webs. |
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What is megaloblastic anemia?
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A group of two anemias that both have impaired DNA synthesis and distinct morph changes in blood. Erythroid precursors and RBC's are usually abnormally large and oval due to defective cell maturation and division. Reticulocyte count is usually low and neutrophils are larger and hypersegmented. Marrow is hyPERcellular.
Two types: pernicious anemia and folate deficiency anemia |
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What causes pernicious anemia?
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A failure of production of IF from atrophic gastritis that causes a Vitamin B12 deficiency.
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VIP
What two reaction require Vitamin B12? |
1. B12 is essential cofactor for enzyme 5-methyltetrahydrofolate-homocysteine methyltrasferase which is used in the production of tetrahydrofolate (THF) which is critical for DNA synthesis.
2. B12 is needed conversion a methylmalonyl coenzyme A to succinyl coA - without there comes an increase of methylmalonate which causes CNS symptoms. |
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Where is the site for folate absorption?
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upper 1/3 of SI
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What does aplastic anemia cause?
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hypocellular marrow (usually increased fat)with anemia, thrombocytopenia, and neutropenia = PANCYTOPENIA
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