Chapter 14- Red Blood Cell Disorders Flashcards by Taylor Horlock

What is anemia?

Reduced total circulating RBC mass (reduced Hb or Hct)

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What are the types of anemias?

Blood loss
Increased RBC destruction
Reduced RBC production

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What are the two types of anemias of blood loss?

Acute- loss of intravascular vol

2. Chronic- rate of loss must exceed marrow regenerative capacity

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How is acute blood loss compensated for?

Interstitial fluid shifts into blood

Blood is diluted

Low Hct triggers EPO production

Increased retics

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What are the two kinds of hemolysis?

Extravascular- RBCs are targeted for sequestration and phagocytosis within the spleen
Intravascular- cells are broken up within the vessels via mech injury, complement, parasites

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What are the characteristics of hemolytic anemias?

Shortened RBC lifespan

Increased EPO

Accumulation of Hb degradation products

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What are the types of hemolytic anemias?

Heredity spherocytosis
G6PD deficiency
Sickle cell disease
Thalassemias
PNH
Immunohemological
Trauma

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What is the defect in hereditary spherocytosis?

Cytoskeletal or membrane protein

Mutation in spectrin or ankyrin

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What causes cell destruction in hereditary spherocytosis?

Spherical cells have diminished deformability and are targeted for extravascular hemolysis

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What is the defect in G6PD deficiency?

Cells can’t reduce glutathione and are prone to oxidative injury

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What is the morphology of G6PD deficiency?

Heinz bodies (Hb ppts) cause hemolysis (extravascular and intravascular)

Bite cells

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What is the defect in sickle cell disease?

Point mutation in beta gloving chain (glu to val) produces HbS

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What are the characteristics of HbS?

Deoxygenation causes polymerization, deforms RBCs

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What affects the degree of sickling?

Interaction with other Hb types (HbF interferes with polymerization)

MCHC

Reduced pH (reduced oxygen affinity)

Reduced microvascular transit time

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What are sickle cell trait individuals protected against?

Falciparum malaria

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What are the characteristics of sickle cell disease?

Chronic hemolysis

Microvascular occlusion

Tissue damage

Splenomegaly

Fibrosis and autosplenectomy

Schistocytes and fragments

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What are the two types of thalassemia?

Beta

2. Alpha

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What is the defect in thalassemia?

Mutations that reduce globin chain synthesis

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What type of anemia does beta thalassemia produce?

Hypo-micro

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What are the two types of beta thalassemia?

Major

2. Minor

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What is the morphology of beta thalassemia?

Inbound alpha chains ppt, cell destruction

Marrow expands (organomegaly)

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What is the morphology of alpha thalassemia?

Free beta tetramers ppt and have a high oxygen affinity (sequestration and hypoxia)

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What is the most severe form of alpha thalassemia and its characteristics?

Hydrops fetalis- all four alpha genes absent

Gamma chains form tetramers (Hb Bart’s)

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What are the characteristics of paroxysmal nocturnal hemoglobinuria?

RBCs are hypersensitive to complement

Thrombosis

Intravascular hemolysis

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What can PNH transform to?

MDS or AML

How does immunohemolytic anemia exert its effects?

Abs attach to RBCs causing their destruction

What are the different types of immunohemolytic anemias?

Warm- IgG Cold- IgM PCH- cold IgG Antigenic drugs- form Ab-cell complexes Tolerance breaking drugs- induce true Ab formation

What is an example of a tolerance breaking drug?

Methyldopa

What kind of hemolysis usually occurs with trauma?

Intravascular

What cells are seen with hemolytic anemia from trauma?

Schistocytes

What can cause trauma to RBCs (and hemolysis)?

Turbulent flow and high shear forces Prosthetic heart valves Diffuse microvascular narrowing

What are possible cause of anemias of diminished erythropoiesis?

Impaired RBC production Deficiency of EPO or viral nutrients Inherited defects Neoplasia SC failure

What are the characteristics of megaloblastic anemias?

Abnormally large RBCs and erythroblasts Anisocytosis and macro-ovalocytes and poikilocytosis PMN nuclear hypersegmentation Defective nuclear maturation

What are the types of megaloblastic anemias?

1. Vit B12 deficiency (pernicious anemia) | 2. Folate deficiency

What is the most common cause of anemias of vit B12 deficiency?

Autoimmune gastritis, loss of IF Reduced B12 absorption

What differentiates anemias of vit B12 deficiency from those of folate deficiency?

CNS lesion only in vit B12 deficiency

What is the most common worldwide nutritional disorder?

Iron deficiency anemia

What type of anemia does iron deficiency produce?

Hypo-micro (reduced Hb)

What are possible causes of iron deficiency?

Low intake Malabsorption Excessive demand Chronic blood loss

What triad is associated with iron deficiency anemia?

Plummer-Vinson Hypo-micro anemia Atrophic glossitis Esophageal webs

How does chronic disease result in anemia?

Inflammation impairs RBC production Low EPO Serum irons low, ferritin high

What type of anemia is associated with chronic disease?

Micro/hypo-normo

What are the characteristics of aplastic anemia?

Chronic primary hematopoietic failure Pancytopenia with hypocellular marrow

What are the categories of aplastic anemia?

1. Toxic exposure 2. Viral infections 3. Inherited diseases

What is pure red cell aplasia?

Form of BM failure due to erythroid precursor suppression

What can cause pure red cell aplasia?

B19 parvovirus Autoimmune diseases Neoplasms

What are some miscellaneous forms of marrow failure?

Myelophthisic anemia (lesions in marrow) Chronic renal failure Hepatocellular liver disease Endocrine disorders (hypothyroidism)

What is polycythemia?

Abnormally high RBC count

What are the two types of polycythemia?

1. Relative (hemoconcentration, reduced plasma volume) | 2. Absolute (increase in RBC mass)

What are the categories of hemorrhagic diatheses?

1. Increased vessel fragility 2. Platelet deficiency/dysfunction 3. Derangement of coagulation

What tests are performed to diagnose bleeding disorders?

PT (extrinsic) PTT (intrinsic) Platelet counts Platelet function tests

What are the possible causes of vessel wall abnormalities?

Infections Drug reactions Poor vascular support Henoch-Schonlein purpura (hypersensitivity yo immune complexes) Hereditary hemorrhagic telangiectasia (dilated, thin walled vessels) Pervascular amyloidosis

What are the characteristics of vessel wall abnormalities?

PT, PTT, platelet count and bleeding time normal Petechiae and purpura

What is thrombocytopenia?

Reduced platelet number (<100000/uL)

At what platelet count is spontaneous bleeding seen?

<20000/uL

What can cause thrombocytopenia?

Reduced production Reduced survival Sequestration Dilution

What are the test results for thrombocytopenia?

PT, PTT and function tests normal Low platelet count

What are the characteristics of immune thrombocytopenic purpura?

Abs against platelets are produced Extravascular hemolysis BT, PT and PTT normal

What are the types of ITP and their characteristics?

1. Chronic- due to chronic disease (SLE, HIV, B-cell neoplasms) 2. Acute- often in children after a viral infection 3. Drug induced- often caused by heparin

What are the two types of drug induced ITP?

1. Rapid after onset, heparin causes platelet aggregation | 2. Delayed (5-14 days) onset, Abs recognize heparin, platelets are activated, thrombosis, life threatening

How can the risk of Type II drip induced ITP be lowered?

Low molecular weight heparin

How can HIV cause thrombocytopenia?

Megakaryocytes express CD4, can be targeted for destruction

What are the two forms of thrombotic microangiopathies?

1. Thrombotic thrombocytic purpura (TTP) | 2. Hemolytic uremic syndrome (HUS)

What are the characteristics of TTP and HUS?

Excessive platelet activation and thrombi deposition in small vessels Widespread hyaline microthrombi (ischemia)

What are the functional areas in which platelets can be effective?

1. Adhesion (BSS or vWD) 2. Aggregation (Glanzmann thrombasthenia) 3. Platelet secretion

What is the characteristic pathology of clotting factor abnormalities?

Large ecchymoses/hematomas after trauma Bleeding into GI, UT and joint spaces

What is the difference between acquired and hereditary abnormalities in cloying factors?

Acquired- multiple abnormalities Hereditary- usually involves a single clotting factor

What hereditary clotting disorders are there?

1. Factor VIII-vWF complex 2. vWD- reduced adhesion 3. Hemophilia A- factor VIII deficiency, prolonged PTT 4. Hemophilia B- factor IX deficiency/Christmas disease, prolonged PTT

What is the most common hereditable bleeding disorder?

vWD

What are the different types of vWD and their characteristics?

Type 1 and 3- reduces levels Type 2- vWF defects

What is DIC?

Excessive activation of coagulation Thrombi formation in microvasculature

What is DIC triggered by?

1. Release of TF or thromboplastic substances | 2. Widespread endothelial injury

In what patients does 50% or DIC occur?

Obstetrics

What are the clinical manifestations of DIC?

Microangiopathic hemolytic anemia (MAHA) Respiratory symptoms Convulsions and coma Oliguria and ARF Circulatory failure and shock

What causes MAHA?

RBCs are damaged by fibrin protein meshworks due to increased coagulation (schistocytes)

What are the types of transfusion complications?

Febrile nonhemolytic Allergic Acute hemolytic (IgM- wrong ABO) Delayed hemolytic (IgG- newly formed) TRALI- neutrophils activated in lungs Infectious complications TACO- physician caused cardiac overload