Red Blood Cell Disorders

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formula for calculating corrected reticulocyte count

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corrected reticulocyte count = (actual Hct/45) x reticulocyte count. 45 = normal Hct

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Corrected reticulocyte count at or above 3% and rct ct below 3%

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above 3% = effective erythropoeisis; below 3% poor bone marrow response to anemia

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Extramedullary hematopoiesis

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liver and spleen: pathogenesis = intrinsic bone marrow dz (myelofibrosis); accelerated erythropoiesis (severe hemolysis in sickle cell dz (radiograph shows "hair on end" appearance)

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anemia in pregnancy

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not a "true anemia" = plasma volume is x2 > than RBC mass (dilutional effect)

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MCV values for micro/macrocytic anemias

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microcytic (<80um3)
normocytic (80-100um3) macrocytic (>100um3)
(average volume of RBCs)

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dec MCHC (mean corpuscular hemoglobin concentration)

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dec: decreased synth of Hb (microcytic anemias) --> central area of pallor greater than nl.

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inc MCHC

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correlates with presence of spherical RBCs (hereitary sperocytosis); no central area of pallor

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RDW (RBC distribution width)

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variation in size of RBCs in peripheral blood = anisocytosis

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inc RDW

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RBCs not uniform in size; iron deficiency = only microcytic anemia with an increased RDW due to a mix of normocytic and microcytic RBCs

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end product of heme degradation in macrophage

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unconjugated bilirubin

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serum TIBC

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concentration of transferrin (inc transferrin and TIBC present in iron deficiency) (dec in transferring and TIBC in ACD and iron overload dz)

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Iron saturation (%)

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represents the percentage of sites on transferrin occupied by iron

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Microcytic anemias

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Iron deficiency, anemia of chronic Dz, thalassemia (a and b), sideroblastic anemia. MCV <80 = defects in the synthesis of Hb (heme+globin chains)

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Macrocytic anemias

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folate def; vit B12 (cobalamin) deficiency

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what are HbH and Hb Bart and what are they assoc w?

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HbH = 4 B Hb chains; Hb Bart = 4 gamma chains (incompat w/ life) assoc w/ alpha thal

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Beta thal minor (B/B+) v. B-thal major (Cooley's anemia; B0/B0)

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Beta thal minor = mild microcytic anemia; mild protective effect against malaria, dec HbA; Beta thal major = severe hemolytic anemia; inc unconj bilirubin; no syth of HbA

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Sideroblastic anemia

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defect in heme sythesis in the mitochondria; ringed sideroblasts; alochol MCC = a mitochondrial toxin; B6 def (isoniazid therapy)

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histo of lead poisoning

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ringed sideroblasts and coarse basophilic stippling (Pb denatures enzymes = Ferrochelatase, Aminolevulinic acid, Ribonuclease)

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Fanconi's syndrome

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lead poisoning --> renal tubule damage: proximal renal tubular acidosis, aminoaciduria, phosphaturia, glucosuria

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phenytoin and anemia

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Phenytoin inhibits intestinal conjugase - inhibits folate absorbtion --> pernicious anemia (macrocytic)

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Alcohol and oral contraceptives and anemia

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reabsorption of folate inhib -> macrocytic anemia

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homocysteine and folate deficiency

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deficiency of folate is most common cause of inc serum homocysteine in US. Homocysteine damages endothelial cells leading to vessel thrombosis.

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Most sensitive test for B12 def

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inc methylmalonic acid

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Pancytopenia, oval macrocytes, hyperseg neutrophils

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B12 or folate def

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pernicious anemia

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lack of IF

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what test is used to localize B12 def

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Schilling test

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dec maternal intake folate:

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inc risk for NT defects

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Normocytic anemias

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acute blood loss, early iron def, anemia of chronic disease, chronic renal failure

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Anemia of chronic renal failure

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dec EPO MCC

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Hemolytic anemias: intrinsic and extrinsic

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intrinsic - defect in RBC (membrane def, abn Hb, enzyme def)
extrinsic - outside RBC (stenotic aortic valve, immune destruction)

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Extravascular hemolysis - macrophage phagocytosis, unconjugated hyperbilirubinemia

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RBCs coated by AgG w or w/o C3b, abn shaped RBCs; inc LDH from hemolyzed RBCs

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Intravascular hemolysis

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enzyme def (def of G6PD), mechanical damage (aortic valve), - hemosiderinuria (renal tubules convert iron in Hb to hemosiderin); dec haptoglobin, inc LDH

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Hereditary Spherocytosis

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intrinsic defect, extravasc hemolysis; mut in ankyrin in cell membrane; inc RBC osmotic fragility

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Hereditary elliptocytosis

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defective spectrin and band 4.1

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Paroxysmal nocturnal hemoglobinuria

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mutation in multipotent myeloid stem cell - loss of anchor for decay accelerating factor (normally, DAF neutralizes complement attached to RBCs, Neutrophils, platelets. Intrinsic defect, intravascular hemolysis (occurs at night becauseresp acidosis enhances complement attachment to these cells)

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Sickle cell anemia

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intrinsic defect, extravascular hemolysis; sickle cell trait (HbAS) - no anemia

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HbF

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prevents sickling of cells

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Dactylitis

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painful swelling of hands and feet in infants due to bone infarcts in sickle cell

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Howell-Jolly bodies

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sign of splenic dysfunction - in HbSS - autosplenectomy by age 2 - spleen fibrosed and diminished in size in young adults

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Sickle cell susceptibility

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to encapsulated bacteria

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Heinz bodies and bite cells

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G6PD deficiency; intrinsic defect, intravascular hemolysis

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G6PD deficiency

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no glutathoine, which usu neutralizes hydrogen peroxide --> oxidizes Hb --> heinz bodies --> in spleen - removes heinz body = bite cell

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RBCs with thorny projections (echinocytes)

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Pyruvate kinase deficiency

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most common cause of autoimmune hemolytic anemia

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SLE

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warm AIHA v Cold AIHA

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warm - IgG, cold - IgM

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Coombs' test (DAT)

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most important marker of immune hemolytic anemia

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Achlorhydria, anti-intrinsic factor, antiparietal cell abs, inc incidence of gastric carcinoma

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pernicious anemia - autoimmune gastritis - failure of production of IF

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lemon-yellow skin color, somatitis, glossitis, demyelination of posterior and lateral cell columns

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pernicious anemia

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Abnormal Schillings test not correcte by IF

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intestinal malabsorption - Crohns dz, blind loops syndrome, and giant tapeworm infestation

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TIBC in anemia of chronic disease

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characteristically decreased

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TIBC in iron deficiency anemia

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increased

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anemia, leukopenia, thrombocytopenia

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pancytopenia in aplastic anemia

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substances that can cause aplastic anemia

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benzene, chloramphenicol, alkylating agents

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Myelophthisic anemia

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replacement of BM, often by a malignant neoplasm