Hematology Lecture Exam 2

Describe how the body communicates that more RBCs are needed.

Erythropoietin

Trends that occur as the normal developing erythrocyte matures.

• Cell size decreases

• Nuclear-cytoplasmic ratio decreases

• The nucleus loses its nucleoli and becomes smaller while the chromatin becomes more dense and stains more intensely

Describe the pronormoblast.

Large size

Large nucleus

8:1 N:C ratio

Prominent nucleolus

Scant light blue cytoplasm

Nucleus with immature chromatin

Describe the basophilic normoblast.

16- 18 microns

Moderately high N:C ratio

Deep blue cytoplasm

Round nucleus with immature chromatin

Describe the polychromatophilic normoblast.

last stage capable of mitosis

Round nucleus with mature chromatin

Intermediate N:C

Greyish cytoplasm

Describe the orthochromic normoblast.

Pyknotic nucleus

Dark and dense nucleus

Low N:C ratio

Greyish-orange cytoplasm

Describe Reticulocytes

lack a nucleus

appear bluish on wright’s stain

Describe the Glycolytic Pathway.

• Anaerobic

• 90-95% of glucose entering the cell is metabolized this way

• Generates ATP for cation pumps

  • Maintain intracellular ions

  • Pumps eventually fall and water flows in RBC

Describe the hexose monophosphate pathway.

5-10% of glucose entering the cell is metabolized this way

Glucose-6-Phosphate dehydrogenase (G6PD): plays oxidative role in the first step of the HMP

Via the HMP, G6PD generates NADPH in the process, which protects cell from oxidative injury

G6PD deficiency —> Heinz bodies

Describe the Luebering- Rapoport Pathway

Prod uces 2,3 DPG- binds to hemoglobin and decreases the affinity of the hemoglobin molecule for oxygen

Pathway stimulated during hypoxia

Generates less ATP but is important in that it enhances oxygen delivery to tissues

Describe the Methemoglobin Reductase Pathway

Is responsible for maintaining iron in its reduced state (Fe 2+)

2% of hemoglobin produced daily is in the form of methemoglobin

Methemoglobin cannot bind or carry oxygen

Methemoglobin reductase reduces ferric iron (Fe 3+) back to ferrous state

Defect in this pathway (inherited or acquired) causes methemoglobinemia which can lead to cyanosis

What is erythropoietin?

Stimulates lineage commitment and maturation of RBC precursor cells in the marrow

What is the structure of hemoglobin?

• 4 protoporphyrin rings

• 4 iron atoms

• 4 globin chains

What is the composition of heme groups?

Protoporphyrin ring

Iron (ferrous) Fe 2+

What are the six types of globin chains?

Adult: alpha, beta, gamma, delta

Embryonic: epsilon, zeta

Normal hemoglobin production is dependent on adequate:

1. Synthesis of protoporyphorin ring

2. Synthesis of globin chain

3. Synthesis of Fe

Describe the biosynthesis of Globin.

• Each of the four globin chains is comprised of ~145 amino acids

• Different Hgb designations are determined by which globin chains are present

• Production of the globin chains differs at various stages of fetal and postnatal life

• Synthesis of globin peptide chains occurs on ribosomes in the RBC cytoplasm

Describe the biosynthesis of Heme.

Protoporphyrins are the precursors of heme

Heme synthesis occurs in the mitochondria and cytoplasm of erythroid precursors in the BM

1. Transferrin delivers ferric iron (Fe 3+), which must be reduced ( to Fe 2+), before it can be incorporated

2. Ferrochelatase puts the reduced iron atom into the porphyrin ring

3. Porphyrin + iron = heme

Heme joins with globin in the cytoplasm

Describe the synthesis of Hgb F

• Formed during liver and BM erythropoiesis

• 2 alpha chains + 2 gamma chains

• Comprises 90-95% of the total Hgb until ~ 35 gestation

• 50-85 % Hgb F at birth

  • Has high affinity for oxygen and is responsible for elevated RBC/Hgb/Hct in fetus and newborn

• Normal adult Hgb F levels: 1-2% (achieved by 2 years of age)

• Levels may increase if other chains are defective

Describe Hemoglobin A.

Major adult Hemoglobin

2 alpha chains + 2 beta chains

Adult levels are reached 6 months to 1 year after birth

Normal adult levels: 95-97%

Describe Hemoglobin A2.

2 alpha chains + 2 delta chains

Delta chain production begins shortly before birth and persists through adult life

Normal adult levels: 2-3%

Describe what happens if hemoglobin has increased oxygen affinity.

The hemoglobin molecule does not readily release its oxygen (decreased release to tissues)

Describe what happens if hemoglobin has decreased oxygen affinity

The hemoglobin molecule releases its oxygen more readily (increased release to tissues).

How do conditions in the lungs increase oxygen affinity?

High oxygen concentration and low carbon dioxide/ waste products promote the uptake of oxygen by the Hgb molecule.

How do conditions in the tissues decrease oxygen affinity?

Lower oxygen concentration and increased Carbon dioxide/heat/acid/waste products promote the release of oxygen from Hgb

How does 2,3-DPG affect oxygenation in the body?

Increased levels of 2,3-DPG promote decreased affinity between oxygen and hemoglobin

What causes the oxygen dissociation curve to shift right?

• Increased Carbon Dioxide

• Increased H+ (acidity)

• Increased 2,3-DPG

• Increased exercise

• Increased temperature

What causes anemia?

Insufficient production or impaired function of hemoglobin (Hgb)

How does the body try to compensate for anemias?

• Increase in erythropoietin production

• Increase in oxygenated blood flow

  • Cardiac output and circulation rate

  • Blood flow to vital organs

  • Oxygen uptake

    • Deepening the amount of inspiration

    • Increase respiration rate

• Increase in oxygen utilization by tissue

• The bone marrow must increase production to meet demands of anemia

• Marrow can compensate for decreased survival to some degree

• Anemia develops if:

  • RBC loss or destruction exceeds the maximum capacity of the BM RBC production

  • The BM RBC production is impaired

What are some symptoms of anemias?

• Weakness and fatigue

• Headache, vertigo, syncope

• Dyspnea and palpitations from light exertion or at rest

What lab results help diagnose anemias?

1. Hgb

2. HCT

3. MCV

4. MCHC

5. Reticulocyte count

6. RBC morphology

How do we classify anemias by morphology?

• Normocytic, normochromic

• Macrocytic

• Microcytic, Hypochromic

What are examples of normocytic, normochromic anemias?

• Chronic hemolytic anemia

• Anemia of chronic renal disease

• Leukemia

• Hypoproliferative disorders

What are examples of Macrocytic anemias?

• Megaloblastic (hypersegmented neutrophils)

  • B12 or folate deficiencies

• Non-megaloblastic

  • Liver disease

  • Chronic alcohol use

• Severe hemolysis (reticulocytosis)

What are examples of microcytic, hypochromic anemias?

• Diminished or defective heme synthesis

  • Iron deficiency anemia

  • Chronic inflammation (iron sequestration)

  • Sideroblastic anemia

  • Lead poisoning

• Diminished or defective globin synthesis

  • Thalassemias

  • Hemoglobinopathies

Describe the cause of Acute Post-hemorrhagic Anemia

Caused by acute blood less

Describe Acute Post-hemorrhagic anemia.

• There are adequate iron stores

• Sequence of events following hemorrhage:

  • Hypovolemia

  • Anemia

  • RBC regeneration

Describe the lab findings of Acute Post-hemorrhagic anemia

• Reticulocytosis/polychromatophilia

  • 3-5 days after hemorrhage

  • Related to magnitude of the bleed (retic % rarely > 15%

• Macrocytosis if retic count is dramatically increased ( RDW also transiently increased)

What is the characteristic features of aplastic anemia?

• Pancytopenia

• Reticulocytopenia

• BM hypocellularity

• Depletion of HSCs

What is the cause of aplastic anemia?

Depletion or Defective stem cells related to:

• Decreased progenitor cells

• BM unresponsive to cytokine stimulation

• Defective BM microenvironment

• Immune mediated: abnormal T lymphs suppress normal growth and differentiation of HSCs in BM

What are findings in aplastic anemia?

Pancytopenia

Neutropenia precedes leukopenia

PLTs <20,000

Reticulocytopenia

Cell morphology: normal

Hypocellular BM (<25%)

What is the characteristic finding of Pure Red Cell Aplasia?

a selective decrease in erythroid precursors

What are characteristics of Diamond-Blackfan anemia?

• EPO: increased

• Iron: increased

• B12/folate: N

• Usually diagnosed in the 1st year of life

• Damaged BFU-E and/or CFU-E

• Treatment with BM transplant or repeated transfusions, iron chelation

What are characteristics of Transient erythroblastopenia of childhood?

• Usually follows a viral infection

• Occurs during first year of life to 10 years of age

• Erythroid precursors absent or markedly decreased in bone marrow

• Remission spontaneous (usually within weeks and permanent)

Describe characteristics associated with anemia associated with chronic renal disease.

• As BUN increases ( > 30 mg/dL), the hemoglobin decreases

  • Elevated serum creatinine

  • Abnormal electrolytes

• Decreased EPO production

• Decreased RBC survival (due to dialysis and/or waste buildup)

• Blood loss due to defective PLT function

• Anemia usually normo/normo unless there is a deficiency in folate or iron

What is pathologic hemolysis?

Increased rate of destruction (lysis) of RBCs, shortening their lifespan

Dec RBCs leads to DEC oxygenation, INC EPO production

BM of an otherwise healthy patient responds by INC RBC production, which leads to reticulocytosis

Describe the normal breakdown of hemoglobin

• Macrophages lyse ingested RBCs

• Hemoglobin separated into heme and globin components

• Recycled:

  • Amino acids (polypeptides) from globin chains

  • Iron from heme rings

• Degraded:

  • Protoporphyrin (to bilirubin)

What are the lab diagnostic values of increased RBC destruction.

• DEC Hgb (>1.0 g/dL per week)

• INC Lactate dehydrogenase (LDH)

  • damage causes LDH to be released

• INC unconjugated bilirubin

  • Lots of breakdown of porphyrin ring

• DEC Haptoglobin

  • Protein that binds w/ free hemoglobin

  • Inc free hemoglobin

• Hemoglobinuria

  • Hgb can be detected in urine

• Hemosiderinuria

Lab Diagnostics: Increased RBC Production

• Blood changes — polychromasia

  • MCV may be INC if marked reticulocytosis

  • RDW may also be INC

• Bone marrow changes —

  • DEC M:E ratio

  • 1:3 —> lots of RBC production

Lab Diagnostics: other useful tests for hemolytic anemias

• Specific morphologic abnormalities

  • Schistocytes, bite cells

  • Erythrophagocytosis — macrophages engulfing RBCs

• Direct Antiglobulin Test (DAT)

  • purpose: to see if pt’s RBCs is coated with Ab

• Osmotic Fragility Test — how fragile the cells are

• Heinz body detection

Describe Paroxysmal Nocturnal Hemoglobinuria (PNH)

• Rare, acquired genetic disorder of the RBC membrane

• Somatic mutation in PSC

• RBC, WBC, and PLT are produced that are abnormally sensitive to injury by complement

What are clinical findings of PNH?

• Irregular episodes of hyperhemolysis

• Reddish-brownish urine indicated hemoglobinuria

• Abnormal renal function due to iron deposition

• IDA or folic acid deficiency may develop

• Infection — leukopenia due to destruction from complement

• Venous thrombosis despite thrombocytopenia

• Progressive BM hypoplasia — starts to slow down production and can completely shut down

What are lab findings associated with PNH?

• Normo/Normo anemia with Hgb 8-10 g/dL

• Leukopenia, thrombocytopenia

• Modest increase in retics ( 5-10%)

  • nRBCs also seen on PB smear

• Intermittent hemoglobinuria

• Constant hemosiderinuria — constant shedding of iron

• Hypocellular BM over time

Describe Hereditary Spherocytosis.

• Abnormality of the RBC membrane

• Proteins that maintain cell shape

• DEC surface volume —>

  • beach ball appearance

  • Decreases ratio

• Peripheral smear: spherocytes; polychromasia

  • MCHC: INC

  • Osmotic fragility: INC

• Clinically: anemia, jaundice, splenomegaly

Describe Hereditary Elliptocytosis.

• Prominence of oval and elongated RBCs

• Loss of stability of membrane

• Membrane develops permanent deformities and remains elliptical

• Peripheral smear: >30% elliptocytes, schistocytes

• Clinically: 90% of cases asymptomatic (usually mild, compensated anemia), 10% show moderate to severe anemia

Describe Hereditary Pyropoikilocytosis.

• Involves thermal instability at higher temps

• Peripheral Smear: bizarre poikilocytes, fragments

• DEC MCV (25-55 fL)

• Clinically: hemolytic anemia present at birth

Describe Hereditary Stomatocytosis.

• Disorder of membrane permeability

• Cells overhydrated, swollen, uniconcave

• Peripheral smear: stomatocytes

• Clinically: mild-to-moderate anemia

Describe G6PD Deficiency.

• Protective mechanisms of glucose metabolism are impaired

• G6PD-deficient RBCs cannot fully recover after exposure to oxidative stress

• Denatured Hgb precipitates as Heinz bodies —> attach to RBC membrane

• INC splenic activity and hemolysis

• Heinz bodies cause increased cation permability, osmotic fragility, cell rigidity, loss of membrane

• Peripheral smear: blister cells, bite/helmet cells, spherocytes

• Clinically: normo/normo, INC retics, hemoglobinuria, jaundice

What are some triggers of acute hemolysis (G6PD Deficiency)?

• Fava beans

• Drugs — anti-malarials

• Moth balls

• Some detergents

• Infections, fever

• Supravital stain to see Heinz bodies

How do you diagnose G6PD deficiency?

• Dependent upon demonstrating DEC G6PD activity in RBCs

• Enzyme activity may appear normal initially after hemolytic episode

  • Older RBC with less G6PD are destroyed during episode

  • Retics remain and have normal G6PD

• Retest for G6PD levels in 2-3 months

Describe Pyruvate Kinase (PK) Deficiency.

• DEC PK ( in EM pathway) leads to DEC ATP

• No normal membrane function

• Loss of water —> cell shrinks —> acanthocytes, echinocytes

• Reticulocytosis

• Normo/normo with Hgb 6-12 g/dL

• Supportive treatment, but usually not needed

Describe Hemolytic anemias caused by extrinsic factors.

• Classification

  • RBCs intrinsically normal

  • Extracellular defect

• Antagonists in the blood

  • Chemicals and drugs

  • Animals venoms

  • Infectious agents, parasites

  • Antibodies to RBC

• Physical injury to the cell

  • Microangiopathic Hemolytic Anemia (MAHA)

    • Disseminated intravascular coagulation

    • Thrombotic thrombocytopenic purpura

    • Hemolytic uremic syndrome (HUS)

  • Malignant Hypertension

  • Thermal injury

  • Prosthetic heart valves