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PCM1 Exam 3 > RHS16 - Red Cell Disorders 1 > Flashcards

RHS16 - Red Cell Disorders 1 Flashcards

1
Q

Give a brief overview of erythropoiesis.

A
  1. Erythropoietin stimulates stem cells in the bown marrow to release erythroid precursors
  2. Precursors mature through various stages of nucleated RBCs in the bone marrow
  3. Nucleus is ejected and reticulocytes are released into circulation
  4. Reticulocytes mature into RBCs in 1-2 days
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2
Q

Describe the basic Hb structure in in fetuses and adults.

A
  • Four globin chains
    • two α chains in both fetuses and adults
    • two β chains in adults
    • two γ chains in fetuses
  • Each globin is bound to one heme molecule containing iron
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3
Q

Define anemia

A

Below normal limits of total circulating red cell mass

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4
Q

What are the RBC parameters we need to know?

A
  • Mean Cell Volume (MCV) - average volume of a RBC
  • Mean Cell Hemoglobin (MCH) - average content of Hb per RBC
  • Mean Cell Hemoglobin Concentration (MCHC) - average [Hb] in a given volume of packed RBCs
  • Red Cell Distribution Width (RDW) - coefficient of variation of RBC volume
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5
Q

What are the common clinical features of mild to moderate anemia?

A
  • Asymptomatic when mild
  • Poor O2 supply to tissues
    • Easy fatigability
    • Headaches
    • Fainting/Dizziness
    • SOB
    • Palpitations
    • Pallor & Nail changes
    • Tachycardia
    • Hemi murmurs (from increased blood velocity in heart)
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6
Q

What are some of the symptoms of severe anemia?

A
  • Worsening of moderate anemia symptoms
  • Angina
  • CHF
  • Confusion
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7
Q

Write out the anemia classification tree.

A
  • Morphological Classifications
    • Normochronic or Hypochromic (hemoglobinization/pinkness)
    • Macrocytic, Normocytic, or Microcytic (size)
  • Pathophysiological Mechanism Classifications
    • Accelerated RBC Loss (acute or chonic)
    • RBC Destruction (hemolytic)
      • Intravascular or Extravascular
      • Intrinsic or Extrinsic
    • Impaired RBC production
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8
Q

List the disorders that can cause the following:

  • Microcytic hypochromic anemias
  • Normochromic normocytic anemias
  • Normochromic macrocytic anemias
A
  • Microcytic hypochromic anemias - iron deficiencies, chronic diseases, lead poisoning, thalassemias
  • Normochromic normocytic anemias - acute blood loss, hemolytic anemia, chronic diseases
  • Normochromic macrocytic anemias - folate deficiency, B12 deficiency
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9
Q

What is this?

A

Hypochromic microcytic anemia

Probably caused by Fe deficiency, chronic disease, Pb poisoning, or thalassemia

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10
Q

What is this?

A

Normochromic macrocytic anemia

Probably caused by a folate or B12 deficiency

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11
Q

How does the body respond, in regard to RBC production, to acute and chronic blood loss?

A

Acute Hemorrhage - increase EPO to stimulate reticulocytosis

Chronic Hemorrhage - underproduction of RBCs develops due to the gradual decrease of iron stores

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12
Q

What features do all types of hemolytic anemias have in common?

A
  • Shortened RBC life span
  • Increased EPO
  • Increased Hb breakdown products
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13
Q

List the causes of intravascular hemolysis

A
  • Mechanical Injury (e.g. - defective cardiac valve, thrombus with sharp edges, heat)
  • Complement Fixation (immune system destroys RBCs)
  • Infections (e.g. - intracellular parasites (malaria), production of toxins (clostridia))
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14
Q

List the causes of extravascular hemolysis. What is usually an observable feature of this?

A
  • Defects that cause spleen phagocytes to prematurely destroy RBCs
    • Defects in RBC shape (spherocytosis, sickle cell, etc)
    • RBC rendered foreign (usually be immune mechanism)

Typically associated with splenomegaly

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15
Q

What is the lab evidence for hemolytic anemia?

A
  • Peripheral Blood Smear - normochromic normocytic with polychromasia (increaseed reticulocytes). Maybe nucleated RBCs
  • Bone Marrow - erythroid hyperplasia
  • Plasma/Serum levels - increased unconjugated bilirubin, LDH (from within the RBCs), and free Hb (if intravascular). Decreased or absent haptoglobin (it’s all bound to the free Hb)
  • Urine - hemosiderinuria and hemoglobinuria (intravascular)
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16
Q
A
17
Q

What are the main causes of intrinsic hemolytic anemias?

A
  • Membrane defects (hereditary spherocytosis)
  • Enzyme defects (G6PD deficiency)
  • Hb defects (sickle cell, thalassemia)
  • Paroxysmal nocturnal hemoglobinuria (PNH) (descruction by complement system)
18
Q

What are the main causes of extrinsic hemolytic anemias?

A
  • Immune mediated damage (autoimmune diseases, drug related, transfusion reaction)
  • Nonimmune damage (mechanical trauma, infections, chemicals, hypersplenism)
19
Q

What is hereditary spherocytosis (HS)? What is the pattern of inheritance and what demographics are at highest risk?

A

A genetic disorder affecting RBC membrane skeleton proteins so that the RBCs become spheroid in shape and less deformable, leading to their destruction by the spleen.

Autosomal dominant

Northern Europeans

20
Q

What is the pathogenesis of HS?

A
  1. Genetic mutation(s) alters the function of Ankyrin, Band 3, Spectrin, and Band 4.2 so that the RBC membrane becomes less stable
  2. Normal shearing stresses in the circulation cause steady loss of small membrane fragment
  3. RBC slowly becomes more spherical
  4. Eventually the spherical RBC gets trapped in the splenic sinusoids and phagocytosed by splenic macrophages
21
Q

What are the clinical features of HS?

A
  • Mild to moderate anemia (sometimes asymptomatic)
  • Splenomegaly
  • Jaundice (unconjugated hyperbilirubinemia)
22
Q

List the lab tests and findings for HS.

A
  • Same tests/results for all hemolytic disorders
  • 75% of HS patients will have FHx
  • MCHC will be increased
  • Howell-Jolly bodies in splenectomized patients
  • Osmotic Fragility Test will confirm presence of spherocytes but not the cause of the spherocytes
  • A negative coombs test will confirm the spherocytes are not the result of an autoimmune disease. Therefore, it must be HS
23
Q

What type of infection is particularly life threatening to HS patients and why? How is this infection treated?

A

Parvovirus B19 depresses erythropoieses which HS patients rely heavily on to keep RBC numbers up. These infections can induce an aplastic/hemolytic crisis.

Usually treated with blood infusions short term and with a splenectomy long term (will correct anemia but spherocytosis persists)

24
Q

What is this?

A

HS with Howell-Jolly bodies, indicating splenectomy

25
Q

Explain how G6PD deficiency causes hemolytic anemia

A
  • RBS are under highe than usualy oxidative stress and rely upon reduced glutathione (GSH) as an antioxidant
  • G6PD is an important part of the reaction pathway that reduces GSH
  • Oxidation of -SH groups on the globin chains leads to their denaturation, precipitation, and deposition onto the RBC membrane as Heinz Bodies
  • Membrane damage leads to intravascular hemolysis, spleen macrophages “biting” out the heinz bodies (forming bite cells), and eventual removal by the spleen (extravascular hemolysis)
26
Q

List the G6PD variants and describe their inheritance patterns

A

All variants are X-linked recessive (mostly affect males)

  • A+ variant - high enzyme levels, no hemolysis
  • A- variant - decreased enzyme half-life (from misfolding) leading to decreased RBC half-life (since mature RBCs can’t make new proteins)
  • Mediterranean variant - more severe than A- variant
  • B variant - normal
27
Q

What is this?

A

G6PD deficiency

Heinz bodies and bite cells

28
Q

Why is G6PD deficiency more common in the mediterranean?

A

Thought to be due to natural selection because it protects agains P. falciparum malaria infections

29
Q

Describe the clinical presentation of G6PD deficiency

A
  • Typically shows signs of acute intravascular hemolytic anemia 2-3 days after exposure to oxidant stress such as:
    • Infections
    • Drugs - antimalrials, sulfonamides
    • Foods - fava beans
  • Less common is neonatal jaundice and chronic low-grade hemolytic anemia
30
Q

What is a G6PD diagnosis based on?

A
  • Clinical Hx
  • CBC
  • Peripheral blood findings
    • normochromic normocytic anemia
    • Heinz bodies
    • Bite cells
    • Polychromatic cells
  • G6PD enzyme assay done outside of a hemolytic episode

PCM1 Exam 3 (31 decks)

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