hematologic pathology p36-47

7/30/2019 Hematologic Pathology p36-47

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RBC Disorders Tues. 10/19/10

Erythropoiesis:

Goal: formation of RBCs oxygen transportSite: bone marrowMain growth factor: erythropoietinDuration: 5 days (from proerythroblast to reticulocyte)Lifespan of RBC: 120 days

Test q: The normal lifespan of RBCs in peripheral blood is: 120 days.

Anemia vs. Polycythemia:

Anemia: Decrease in Hgb and hematocrit levels inrelation to age- and sex-adjusted normal ranges.

- Signs: Pallor, Fatigue, Dizziness,Tachycardia, Shortness of breath

Polycythemia: Increase in hemoglobin and hematocrit ascompared to normal ranges

- Signs: Headache, Pruritus, Dizziness

Red cell indices:- Hemoglobin (Hb) : concentration, in g/dL- Hematocrit (Hct) : proportion of blood volume that

is occupied by RBCs- Mean cell volume (MCV) : average volume of

RBC expressed in femtoliters- Mean cell hemoglobin (MCH) : average mass of

hemoglobin per RBC, in picograms- Mean cell hemoglobin concentration (MCHC) :

average concentration of hemoglobin in dL ofpacked RBCs, g/dL

- RBC distribution width (RDW) : CV of RBCvolume, size variability

Can separate RBCs from the rest of the blood.


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Determining the Concentration of Hemoglobin: RBC distribution width (RDW):

Figure: The potassiumferricyanide oxidizeshemoglobin to hemiglobin(Hi; methemoglobin), andpotassium cyanide providescyanide ions (CN-) to formHiCN, which has a broadabsorption maximum at awavelength of 540 nm.

Figure: RDW Abnormal in

anisopoikilocytosis(abnormally shaped RBCs).

Adult Reference Ranges for RBCs:

The reference ranges for the laboratory providingthe result should always be used in interpreting

the test result.

Advantages of theelectronic cell counter- Speed of performance- elimination of visual

fatigue of the technician- Improved precision are

decisive

Morphologically discernable stages oferythroid development:

Proerythroblast Basophilic erythroblast Bone Polychromatophilic erythroblast marrow Orthochromatic erythroblast

Reticulocyte Mature RBC Blood

Maturation:

When passing through bone marrow sinus, nucleusis extruded.


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Reticulocyte count: Enumeration of reticulocytes indicates production of new red blood cells by the marrow

Manual using supravital dye to precipitate residual RNA Automated in a cell counter

Corrected reticulocyte count: actual patient value corected with an expected release of reticulocytes in health

Polychromasia:

Polychomatophilic more purplish/bluish

Reticulocytes Supravital stain: Automated Reticulocyte count: RNA binding dye

Reticulocyte count:Decreased Iron deficiency B12/folate deficiency Anemia of chronic disease Primary marrow neoplasms Aplastic anemia

Increased Hemolytic disorder Treatment of iron or

B12/folate deficiencywith response

Bleeding

Anemia: Reduction of the total circulating red cell mass belownormal limits reduces the oxygen-carrying capacity of the blood, leadingto tissue hypoxia In practice, the measurement of red cell mass is not easy,and anemia is usually diagnosed based on a reduction inthe hematocrit and the hemoglobin concentration of theblood to levels that are below the normal range

Anemia: Clinical features Pale, weakness, malaise, and easy fatigability O2 dyspnea, fatty change in the liver, myocardium,and kidney Hypoxia

Myocardial angina pectoris, particularly whencomplicated by pre-existing coronary artery disease

CNS headache, dimness of vision, and faintness

Reticulocyte:Wright-Giemsa Supravital

Live-nonfixed cells

Methylene blue/brilliantcresyl blue

Polychromasia Substantia reticulofilamentosa(purple tinge) (Amount of precipitated RNA

decreases w/age of the

reticulocyte.)

Test q: Reticulocytes are DECREASED in all of the followingEXCEPT: Hemolytic anemia. (Other choices: Aplastic anemia, Iron

deficiency anemia, Leukemia, and Folate deficiency.)Test q:A healthy 19F suffered blunt abdominal trauma in a motorvehicle accident. On admission to the hospital, her initial hematocrit

was 33%, but over the next hour, it dropped to 28%. A paracentesisyielded serosanguineous fluid. She was taken to surgery, where aliver laceration was prepared and 1 L of bloody fluid was removed

from the peritoneal cavity. She remained stable. A CBC performed3 days later is most likely to show which of the following morphologicfindings in RBCs in the peripheral blood? Reticulocytosis. (=

increase in reticulocytes)


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Anemia according to underlying mechanism: BLOOD LOSS INCREASED RED CELL DESTRUCTION (HEMOLYSIS) DECREASED RED CELL PRODUCTION

Classification of anemia based on MCV and RDW:

Above: Different problems correlate with different steps in maturation.

ANEMIAS OF BLOOD LOSS: Acute Blood Loss loss of intravascular volume massive -cardiovascular shock, and death.

rate of hemorrhage, external or internal bleeding O2 erythropoietin from the kidney proliferation

of committed erythroid progenitors (CFU-E) in themarrow 5 days reticulocytes

ANEMIAS OF BLOOD LOSS: Chronic Blood Loss Chronic blood loss induces anemia only when the rate of loss exceeds the regenerative capacity of the marrow or

when iron reserves are depleted and iron deficiency anemia appears

Microcytosis pattern: Normal RBC size ~ nucleus of small lymphocyte Most common causes:

Iron deficiency Hemolysis Thalassemia (globin synthesis defect)

MCV Normal RDW High RDW

Microcytic100 fL

Aplastic anemia Myelodysplastic

syndromes

B12/folatedeficiency

Liver disease Alcohol Thyroid

insufficiency Myelodysplastic

syndromes

Anemia paleness ofmucosa and skin.


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Iron deficiency: Most common cause of anemia across the age

groups Most common nutritional deficiency world-wide US: toddlers, adolescent girls, and women of

childbearing age Iron present as:

Functional (hemoglobin, myoglobin.enzymes)

Storage iron (ferritin, hemosiderin) 15-20%total Intracellular ferritin (aggregates form

hemosiderin) and plasma ferritin Hemosiderin prominent in iron overload Transferrin as transporter of iron in plasma

Test q:Among the following, the most common cause of anemiais: iron deficiency. (Other choices: Bone marrow replacement

by cancer, Intravascular hemolysis, Genetic defect in hemoglobinsynthesis, and Vitamin deficiency.)

Most of Fe control occurs through intestinal absorption.

Normal= 33% saturation= iron level of

100-120ug/dL= total iron binding

capacity 300-350ug/dL

Iron deficiency Ferritin (reflects iron storage pool) - low % saturation -


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Figure: Iron stain of bone marrow (Prussian blue stain) Macrophages laden with iron.

Etiology:1. dietary lack2. impaired absorption3. increased requirement4. chronic blood loss(most importantly). normal iron balance, 1 mg of

/day

Many women consume marginally adequate amounts of iron Heme iron is much more absorbable than inorganic iron Infants: high risk due to the very small amounts of iron in milk The impoverished: suboptimal diets for socioeconomic reasons The elderly: restricted diets with little meat because of limited income or poor dentition.

Teenagers: junk food.

Chronic blood loss: The most common cause of iron deficiency in the Western world. Iron deficiency in adult men and postmenopausal women in the Western world must be attributed to gastrointestinal

blood loss until proven otherwise.

Chronic Blood loss: GI source Hereditary telangiectasia

Polyp Adenocarcinoma

Test q:A 65M has experienced worseningfatigue for the past 9 months. On phys exam,

he is afebrile and has a pulse of 91/min,respirations 18/min, and blood pressure105/60 mm Hg. There is no organomegaly. A

stool sample is positive for occult blood. Lab

findings include Hgb 5.9 g/dL, hematocrit17.3%, MCV 66m3, platelet count

250,000/mm3, and WBC count 7800/mm

3.

The reticulocyte concentration is 3.9%. Nofibrin split products are detected, and the

direct and indirect Coombs test results arenegative. A bone marrow biopsy specimenshows marked erythroid hyperplasia. Which

of the following conditions best explains thesefindings? Chronic blood loss. (Otherchoices: Vitamin B12 deficiency, Aplastic

anemia, Metastatic prostatic adenocarcinoma,Autoimmune hemolytic anemia.)


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Iron deficiency: Microcytic hypochromic anemia(hypochromia low MCH before microcytosis)

Anisopoikilocytosis (increased RDW)

Confirmation with iron studies: Low ferritin Low % saturation Low iron level High TIBC

Decreased reticulocyte count

Test q:A 29F and mother of 7 children is short of breath and complains of fatigue. The youngest childwas born two years ago. Her serum iron is low and the TIBC is increased. She has not been treated

for her anemia. You expect the reticulocyte count to be: decreased. The patient has blood drawn for aCBC. You would expect the RDW to be: increased.

Stages of Iron Deficiency:

Marrow RE FePlasma FeTIBC

HgbHypchromiaMicrocytosisFerritinFEP

Normal2-3+75-150ug/dl300-400 ug/dl

13-15 gm/dl--12-300 ng/ml30-70 ug//dl

Iron defno anemia0N orN or

N--


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Hemolytic anemias: Hereditary

Membrane defects: hereditary spherocytosis Abnormalities in red cell enzymes: G6PD deficiency Abnormalities of hemoglobin synthesis: thalassemias, hemoglobin S, hemoglobin C

Acquired Immune: infections (malaria), alloantibodies (Rh incompatibilities, incompatible transfusion), autoantibodies

(autoimmune disease, lymphomas) Non-immune: mechanical damage (artificial heart valves, DIC), membrane abnormalities (paroxysmal nocturnal

hemoglobinuria)

Hereditary spherocytosis: RBC membrane disorder (mutations of genes encoding for membrane cytoskeleton membrane cytoskeletal protein) Cell membrane inflexibility-RBC becomes spheroid and less deformable (increased splenic sequestation)

At every step, lose a piece of membrane to compensate.

Proteins in RBC membrane:

Test q:A 30F has had a constant feeling of lethargy since childhood.On phys exam, she is afebrile and has a pulse of 80/min, respirations

of 15/min, and blood pressure of 110/70 mmHg. The spleen tip ispalpable, but there is no abdominal pain or tenderness. Lab studiesshow Hgb 11.7 g/dL, platelet count 159,000/mm

3, and WBC count of

5390/mm3. The peripheral blood smear shows spherocytosis. The

circulating RBCs show an increased osmotic fragility. An inheritedabnormality in which of the following RBC components best accounts

for these findings? Membrane cytoskeletal protein. (Other choices:G6P dehydrogenase, -globin chain, -globin chain, heme)

REPEATED x5


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Normal Spherocyte Elliptocyte Stomatocyteerythrocyte (ankyrin defect) (spectrin defect) (tropomyosin defect) Acanthocyte

Spherocyte:

In contrast to microcytic hypochromia, these are Anisocytosis, Spherocytes, Howell-Jolly bodies, MCHCvery round and dark due to higher Hgb concentration.

Types of Membrane Loss Leading to Pathophysiology ofSpherocyte Formation: hereditary spherocytosis:

Young HS red cells arenormal in shape, but thedeficiency of membraneskeleton reduces the stabilityof the lipid bilayer, leading tothe loss of membranefragments as red cells age inthe circulation.

The loss of membranerelative to cytoplasm forcesthe cells to assume the

smallest possible diameterfor a given volume, namely,a sphere


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Hereditary spherocytosis: Anemia

Lifespan 10-20 days erythropoiesis (to compensate) insufficient to compensate

Splenomegaly (reflection of normal spleen function) Splenectomy beneficial

Jaundice Gallstones (pigment bilirubin) Diagnosis:

Family history Osmotic lysis test

Clinical Features: Compensated- in 20% to 30% of patients asymptomaticAplastic crises

Parvovirus kills red cell progenitors Because of the reduced life span of RBCs, cessation of erythropoiesis for even short time periods leads to

sudden worsening of the anemia Hemolytic crises

increased splenic destruction of red cells (e.g., infectious mononucleosis);

G6PD deficiency: Role of (G6PD) in defense against oxidant injury: G6PD deficiency is a recessive X-linked trait, Several

hundred genetic variants G6PD- and G6PD Mediterranean, cause most of the

clinically significant hemolytic anemias. G6PD- is present in about 10% of American blacks;

G6PD Mediterranean, is prevalent in the Middle East.

Test q: Three days after taking an anti-inflammatory medication that includes phenacetin, a

23y/o African American man passes dark reddish brown urine. He is surprised by thisbecause he has been healthy all his life and has had no major illnesses. On phys exam, heis afebrile, and there are no remarkable findings. CBC shows a mild normocytic anemia, but

the peripheral blood smear shows precipitates of denatured globin (Heinz bodies)w/supravital staining and scattered bite cells in the population RBCs. Which of the following

is the most likely diagnosis? Glucose-6-phosphate dehydrogenase deficiency.REPEATED x2

G6PD deficiency:Episodic hemolysis exposures that generate oxidant stress:

- infections- drugs- foods: fava bean, which generates oxidants when metabolized

FavismCross-linking of reactive sulfhydryl groups on globin chains, which becomedenatured and form membrane-bound precipitates known as Heinz bodiescan damage the membrane


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Sickle Cell Disease: Hereditary hemoglobinopathy Autosomal recessive

Point mutation in the 6th

position of globin chain (ValineGlutamic

acid) Aggregation and polymerization of HbS in low oxygen conditions 8% African Americans are heterozygous for this mutation (40% of the Hbis HbS)

Figure: Anisocytosis, poikilocytosis, sickle cells (drepanocytes),target cells, Howell-Jolly bodies Sickle Cell Disease: Pathogenesis

Can result in infarct of various organs or microvascular occlusion.

Test q:A 40M who has had chronic anemia since childhood is admitted to the hospital w/fever and chest pain. On phys exam, his temp is 38.7C. A

chest radiograph shows extensive patchy infiltrates. Lab studies include a blood culture positive forStreptococcus pneumoniae. Despite supportivetherapy, he dies a few days later. At autopsy, there is a small, fibrotic, 5g spleen filled with deposits of iron and calcium and prominent expansion of themarrow space in the skull. Which of the following conditions is most likely to have resulted in these findings? Sickle cell anemia.

Test q:A 4F of Mediterranean ancestry is diagnosed w/Sickle Cell Anemia. It is important that she be vaccinated ASAP for: Streptococcus

pneumoniae.Test q:A 20M black sickle cell patient should have been vaccinated to prevent infection by: Streptococcus pneumoniae.

Test q:A 17y/o black man w/a known history of sickle cell disease presents to the ER complaining of left upper quadrant pain suggestive of a splenicinfarct. Microscopic exam of the spleen would most likely reveal: coagulative necrosis.

Spleen in sickle cell disease:

Sickle cells clogging up a sinusoid

Sickle Cell Disease laboratory diagnosis:

Hemoglobin electrophoresis: may only have 1 type of Hgb.

SC Disease: 90% HbSSC trait: 40% HbS and 60% HbA

Clinical Course:- Anemia- Painful crises:

microocclusions/infarcts of bone,lung, liver

- Chronic hemolysis withhyperbilirubinemia

- Splenic autoinfarction withinfections with encapsulated

bacteria (H. influenzae, S.pneumoniae)

- Aplastic crisis associated withParvovirus infection

SCD, homozygous


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Sickle cell Solubility Test:

Above: Sickle cell solubility test. In this test, whole blood is added to a high phosphate buffer w/saponin and sodiumdithionite, which causes the hemoglobin to become deoxyhemoglobin. Deoxyhemoglobin S is insoluble. The turbidity ofthe sample on the left indicates the presence of HbS. The clear sample on the right contains no HbS.

Thalassemia syndromes: Heterogeneous group of disorders leading to decreased synthesis of or chains of adult hemoglobin, HbA

Thalassemias:

Thalassemias: Globin Synthesis:

Thalassemia syndromes: Heterogeneous group of disorders leading to decreased synthesis of or chains of adult hemoglobin, HbA

0when homozygous associated with total absence of chain;

+some residual production of chain

Above: eta globin gene (arrows indicate mutations)

Test q:A 35yo apparently healthy man undergoes a medical exam while applying for lifeinsurance. He is not anemic. His hemoglobin electrophoresis is reported as: HbA 62%, HbS

35%, HbF 1%, HbA2 1%; no variant C, D, G, or H bands detected. The most likely diagnosis iswhich of the following? Sickle trait.Test q: In Sickle Cell disease (homozygous), the percentage of hemoglobin that is SS is: 90%.

Test q:A 12M has a history of episodes of severe abdominal and back pain since earlychildhood. On phys exam, he is afebrile, and there is no organomegaly. Lab studies show Hgb11.2 g/dL, platelet count of 194,000/mm

3, and WBC count of 9020/mm

3. The peripheral blood

smear shows occasional sickled cells, nucleated RBCs, and Howell-Jolly bodies. Hemoglobin

electrophoresis shows 1% Hgb A2, 6% HbF, and 93% HbS. Hydroxyurea therapy is found to bebeneficial in this patient. Which of the following is the most likely basis for its therapeuticefficacy? Increase in production of HbF. (Other choices: Increase in production of HbA,decrease in overall globin synthesis, stimulation of erythrocyte production, increase in oxygenaffinity of hemoglobin)

Test q:A patient presents w/a microcytic hypochromic anemia. The PBS shows microcyticRBCs w/many target forms. Splenomegaly is present. The next diagnostic tests one shouldorder is/are: TIBC and Hgb electrophoresis.

hematologic pathology p36-47

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