Definition of Anemia Deficiency in the oxygen-carrying capacityof the blood due to a diminishederythrocyte mass. May be due to: Erythrocyte loss (bleeding) Decreased Erythrocyte production low erythropoietin Decreased marrow response to erythropoietin Increased Erythrocyte destruction(hemolysis)
Measurements of Anemia Hemoglobin = grams of hemoglobin per 100 mL ofwhole blood (g/dL) Hematocrit = percent of a sample of whole bloodoccupied by intact red blood cells RBC = millions of red blood cells per microL of wholeblood MCV = Mean corpuscular volume If > 96 → Macrocytic anemia If 76 – 96→ Normocytic anemia If < 76 → Microcytic anemia RDW = Red blood cell distribution width = (Standard deviation of red cell volume ÷ mean cellvolume) × 100 Normal value is 11-15% If elevated, suggests large variability in sizes of RBCs
RBC Life Cycle In the bone marrow, erythropoietinenhances the growth of differentiation ofburst forming units-erythroid (BFU-E) andcolony forming units-erythroid (CFU-E) intoreticulocytes. Reticulocyte spends three days maturing inthe marrow, and then one day maturing inthe peripheral blood. A mature Red Blood Cell circulates in theperipheral blood for 100 to 120 days. Under steady state conditions, the rate ofRBC production equals the rate of RBC loss.
Classification of Anemia Anemia can be either acute or chronic. In acute anemia (sudden loss of blood), the lack of bloodvolume in the circulatory system is more important thanthe deficiency of hemoglobin. A loss up to 10% of bloodvolume, as that taking place upon blood donation, is welltolerated. Losses between 10 and 20% cause posturalhypotension, dizziness and faint. In losses above 20%,theres tachycardia, cold extremities, extreme palenessand hypotension, followed by shock; should the losssurmount 30%, without immediate replacement ofintravenous fluids, the shock rapidly becomesirreversible and fatal. In chronic anemia, theres no decrease in blood volume,which is compensated by an increase in plasma volume
Classification of Anemia onthe Basis of MCV Microcytic anemia(MCV<76) Normocytic anemia(MCV=76-96) Macrocytic anemia(MCV>96)
Classification Based onunderlying Process Blood loss or def. of nutrients Hemolysis Failure of production
Classification of Anemia One way to classify anemia is by RBC size (i.e., MCV), asmicrocytic, macrocytic, or normocytic. For the microcyticanemias, the etiologic possibilities are iron deficiency,thalassemia, sideroblastic anemia, and the anemias of chronicdisease. Severe microcytic anemia (MCV <70 fL) is causedmainly by iron deficiency or thalassemia. Macrocytic anemiamay be the result of megaloblastic (folate or vitamin B12deficiency) or nonmegaloblastic causes. Folate deficiency can inturn be due to either reduced intake or diminished absorption.Severe macrocytic anemia (MCV >96fL) is almost alwaysmegaloblastic. In some rare cases, macrocytic anemia isrelated to the myelodysplastic syndromes prior to or afterchemotherapy. The causes of normocytic anemias include aplastic anemia,bone-marrow replacement, pure red-cell aplasia, anemias ofchronic disease, hemolytic anemia, and recent blood loss. Anumber of anemias have a genetic etiology. Examples of suchinherited disorders include hereditary spherocytosis andsickle-cell (SC) anemia
Hypochromic Microcytic AnemiaMicrocytic anemiasthe etiologic possibilities are Iron deficiency Thalassemia Sideroblastic anemia Anemias of chronic disease.Severe microcytic anemia (MCV <76 fL) iscaused mainly by iron deficiency or thalassemia.
Iron Deficiency Anemia – LabFindings Serum Iron LOW (< 60 micrograms/dL) Total Iron Binding Capacity (TIBC) HIGH ( > 360 micrograms/dL) Serum Ferritin LOW (< 20 nanograms/mL) Can be “falsely”normal in inflammatorystates
TEST Iron def ThalMin An of ch dis S.Iron - low normal normal S.Ferritin - low N/H N/H Marrow iron - low N/H N/H Hb A2 or F - N H=Bthal N N=Athal RDW - high normal N/H
Thalassemia Microcytic anemia Defects in either the alpha or beta chains ofhemoglobin, leading to ineffectiveerythropoiesis and hemolysis α-thalassemia: Prevalent in Africa, Mediterranean, MiddleEast, Asia β-thalassemia: Prevalent in Mediterranean, South EastAsia, India, Pakistan Smear shows microcytosis with target cells
The causes of normocytic anemias include aplasticanemia, bone-marrow replacement, pure red-cellaplasia, anemias of chronic disease, hemolytic anemia,and recent blood loss. A number of anemias have agenetic etiology. Examples of such inherited disordersinclude hereditary spherocytosis, sickle-cell (SC) anemia,and thalassemia
Macrocytic anemia may be the result of megaloblastic(folate or vitamin B12 deficiency) or nonmegaloblasticcauses. Folate deficiency can in turn be due to eitherreduced intake or diminished absorption. Severemacrocytic anemia (MCV >125 fL) is almost alwaysmegaloblastic.
Anemia due to Destruction ofRed Blood Cells Hemoglobinopathies Sickle Cell Anemia Aplastic Anemia Decrease in all lines of cells – hemoglobin,hematocrit, WBC, platelets Parvovirus B19, EBV, CMV Acquired aplastic anemia Hemolytic Anemia
Hemolytic Anemias Hereditary spherocytosis Glucose-6-phosphatedehydrogenase (G6PD)Deficiency Most common enzyme defect inerythrocytes X-linked Brisk hemolysis when patientsexposed to oxidative stress fromdrugs, infections or toxins. Thrombotic ThrombocytopenicPurpura (TTP) Thrombocytopenia andmicroangiopathic hemolyticanemia, fever, renalinsufficiency, neurologicsymptoms Schistocytes on smear Hemolytic Uremic Syndrome Thrombocytopenia,Microangiopathic hemolyticanemia, renal insufficiency Autoimmune Hemolytic Anemia Warm-antibody mediated IgG antibody binds to erythrocytesurface most common Diagnosed by POSITIVE Coomb’sTest (detectgs IgG or complementon the cell surgace) Can be caused drugs Treated with corticosteroids orsplenectomy if refractory Cold agglutinin Disease IgM antibodies bind to erythrocytesurface Does not respond to corticosteroids,but usually mild. Infections Malaria Babesiosis Sepsis Trauma Includes some snake, insect bites