Thalassemia and Hemoglobin Types
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Questions and Answers

Which genotype represents a carrier for the defective allele?

  • B
  • bb
  • BB
  • Bb (correct)

In a cross between two carrier parents (Bb x Bb), what is the probability of having an affected child?

  • 50%
  • 100%
  • 75%
  • 25% (correct)

What is a likely consequence of the gene deletion in alpha thalassemia?

  • Complete absence of hemoglobin
  • Increased globin synthesis
  • Microcytic anemia (correct)
  • Normal hemoglobin production

What characterizes the beta thalassemia condition?

<p>Deficiency of beta chain synthesis (C)</p> Signup and view all the answers

What percentage of offspring will be carriers when a BB parent is crossed with a bb parent?

<p>50% (D)</p> Signup and view all the answers

In a Bb x Bb genetic cross, what proportion of offspring will have a normal genotype?

<p>75% (C)</p> Signup and view all the answers

What is the primary defect in hemoglobin production in thalassemia?

<p>Imbalance of globin chain synthesis (D)</p> Signup and view all the answers

Which of the following genotypes would result in all children being affected?

<p>bb x bb (A)</p> Signup and view all the answers

What genetic variation results in a carrier parent phenotype?

<p>Heterozygous (A)</p> Signup and view all the answers

What type of anemia results from thalassemia due to defective hemoglobin production?

<p>Hypochromic anemia (A)</p> Signup and view all the answers

What is the primary type of hemoglobin found in adults?

<p>Hb A α2β2 (B)</p> Signup and view all the answers

How does fetal hemoglobin (Hb F) compare to adult hemoglobin in terms of oxygen binding?

<p>Hb F binds oxygen more strongly than adult hemoglobin. (A)</p> Signup and view all the answers

What is true regarding the decrease of Hb F levels in newborns?

<p>Hb F levels decrease to adult levels within the first year. (C)</p> Signup and view all the answers

Which of the following statements about homozygous and heterozygous genotypes is accurate?

<p>Homozygous individuals may have a higher risk of hereditary disorders. (B)</p> Signup and view all the answers

What is the main role of beta thalassemias in relation to hemoglobin F levels?

<p>They can delay the decrease of Hb F levels. (B)</p> Signup and view all the answers

Which embryonic hemoglobin is composed of two zeta and two epsilon chains?

<p>Hb Gower 1 (C)</p> Signup and view all the answers

How many genes contribute to the structure of alpha globin protein chains?

<p>Two genes from each parent. (B)</p> Signup and view all the answers

Which hemoglobin type is primarily produced during fetal development?

<p>Hb F (D)</p> Signup and view all the answers

What type of erythrocytes are predominantly observed in the peripheral blood of Beta Thalassemia Major?

<p>Hypochromic and microcytic with extreme poikilocytosis (A)</p> Signup and view all the answers

What is the most significant risk associated with continuous transfusion therapy in patients with Beta Thalassemia?

<p>Development of iron overload leading to hemosiderosis (B)</p> Signup and view all the answers

What characterizes the hemoglobin profile in a patient with Beta Thalassemia Major?

<p>Dominance of Hb F with a slight increase in Hb A2 (C)</p> Signup and view all the answers

Which factor contributes to the ineffective erythropoiesis seen in Beta Thalassemia Major?

<p>Complete absence of β-chain synthesis (B)</p> Signup and view all the answers

What is the most common compensatory response to the anemia caused by Beta Thalassemia?

<p>Extramedullary hematopoiesis in the spleen and liver (D)</p> Signup and view all the answers

Which of the following statements correctly describes the pathophysiology of Beta Thalassemia?

<p>There is an excess of α-chains that precipitate within normoblasts. (B)</p> Signup and view all the answers

What is a notable observation in the red blood cell morphology of patients with Beta Thalassemia Major?

<p>Marked basophilic stippling and numerous NRBCs (C)</p> Signup and view all the answers

What complications can arise from repeated blood transfusions in patients with Beta Thalassemia?

<p>Development of alloimmunization and risk of transfusion-transmitted diseases (C)</p> Signup and view all the answers

What percentage of normoblasts in the bone marrow typically undergo apoptosis in Beta Thalassemia?

<p>70-80% (A)</p> Signup and view all the answers

In Beta Thalassemia Major, why is there an increased destruction of red blood cells?

<p>Resulting from sequestration of inclusion-bearing red cells in the spleen (D)</p> Signup and view all the answers

What is the predominant hemoglobin present in Bart’s Hydrops Fetalis Syndrome?

<p>Hemoglobin Bart (C)</p> Signup and view all the answers

What percentage of Hemoglobin H can be found in individuals with Hemoglobin H disease?

<p>2-40% (C)</p> Signup and view all the answers

Which characteristic best describes the red blood cells in individuals with Hemoglobin H disease?

<p>Microcytic and hypochromic (C)</p> Signup and view all the answers

What complications are mothers at increased risk of during pregnancies complicated by Bart’s Hydrops Fetalis Syndrome?

<p>Toxemia and severe postpartum hemorrhage (B)</p> Signup and view all the answers

In individuals with silent carrier alpha thalassemia, which type of hemoglobin is present in the lowest percentage?

<p>Hemoglobin Bart (D)</p> Signup and view all the answers

What is a notable morphology of the red cells observed in Hemoglobin H disease when stained?

<p>Golf ball appearance (D)</p> Signup and view all the answers

What genetic factor characterizes Bart’s Hydrops Fetalis Syndrome?

<p>Absence of functioning alpha chain genes (C)</p> Signup and view all the answers

What is a characteristic feature of Delta Beta Thalassemia?

<p>Only alpha and gamma chains are produced (C)</p> Signup and view all the answers

Which statement accurately describes Beta Thalassemia with Hb S?

<p>Severity of symptoms varies depending on the amount of HbA produced (A)</p> Signup and view all the answers

What are the common features of Beta Thalassemia with Hb C?

<p>Results from inherited variations from both parents (A)</p> Signup and view all the answers

In Delta Beta Thalassemia, what is notably elevated in heterozygous individuals?

<p>HbF (B)</p> Signup and view all the answers

What defines the hemoglobin profile in homozygous Delta Beta Thalassemia?

<p>Absence of both HbA and HbA2 (B)</p> Signup and view all the answers

What is a typical symptom of Beta Thalassemia with Hb S when no HbA is produced?

<p>True sickle cell symptoms (C)</p> Signup and view all the answers

Which of the following is NOT typically associated with Delta Beta Thalassemia?

<p>Severe anemia from birth (B)</p> Signup and view all the answers

How does Beta Thalassemia with Hb C affect hemoglobin structure?

<p>It causes an amino acid substitution in the beta chain (A)</p> Signup and view all the answers

What distinguishes sickle beta thalassemia from other forms of beta thalassemia?

<p>It combines symptoms of sickle cell disease with beta thalassemia (B)</p> Signup and view all the answers

What is a significant consequence of the gene deletion in Delta Beta Thalassemia?

<p>Simultaneous reduction of δ and β-globin chain production (C)</p> Signup and view all the answers

Flashcards

Thalassemia

A group of inherited blood disorders caused by defects in the genes that produce hemoglobin.

Hemoglobin (Hb)

The protein in red blood cells that carries oxygen throughout the body.

Hb A

The most common type of adult hemoglobin (α2β2).

Hb F

Fetal hemoglobin (α2γ2), produced during pregnancy and early childhood.

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Homozygous

Having two identical copies of a gene (e.g., both mutated).

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Heterozygous

Having two different copies of a gene (e.g., one normal and one mutated).

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Alpha Thalassemia

A form of thalassemia caused by defects in alpha globin genes.

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Beta Thalassemia

A form of thalassemia caused by defects in beta globin genes.

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Homozygous genotypes

Genotypes where both alleles for a gene are the same (e.g., BB or bb).

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Heterozygous genotypes

Genotypes where the two alleles for a gene are different (e.g., Bb).

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Dominant allele

An allele that is expressed even if only one copy is present.

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Recessive allele

An allele that is only expressed if two copies are present.

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Hemoglobin

Protein in red blood cells that carries oxygen.

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Erythropoiesis

Process of red blood cell production.

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Gene Deletion

Loss of a segment of DNA from a chromosome.

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Beta Thalassemia Major

A genetic blood disorder characterized by reduced or absent beta-globin production, leading to impaired red blood cell production, and requiring frequent blood transfusions.

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Hypochromic, microcytic erythrocytes

Red blood cells that are pale (hypochromic) and small (microcytic) due to reduced hemoglobin.

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Poikilocytosis

Abnormal variations in the shapes of red blood cells.

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Target cells, teardrop cells, elliptocytes

Examples of abnormal red blood cell shapes seen in beta-thalassemia.

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Basophilic stippling

Tiny dark-staining granules seen in red blood cells, suggesting problems with hemoglobin production.

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Iron overload (hemosiderosis)

A complication of frequent blood transfusions due to excess iron accumulation in the body.

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Alloimmunization

Development of antibodies against transfused red blood cells.

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Ineffective erythropoiesis

Impaired red blood cell production within the bone marrow, a key feature in beta-thalassemia.

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Extravascular hemolysis

Destruction of red blood cells outside the blood vessels.

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Hepatosplenomegaly

Enlargement of both the liver and spleen, often seen in conditions like thalassemia.

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Delta Beta Thalassemia

A group of disorders caused by gene deletions affecting both delta and beta globin genes, leading to reduced production of δ and β chains.

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What happens in Delta Beta Thalassemia?

Only alpha and gamma chains are produced, causing a reduction in both δ and β globin chains. This resembles beta thalassemia minor and is often asymptomatic.

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Beta Thalassemia with Hb S

A combination of sickle cell disease and beta thalassemia, characterized by both abnormal hemoglobin (Hb S) and reduced beta globin chain production.

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Hb A production in Beta Thalassemia with Hb S

The amount of Hb A produced varies, ranging from none to varying amounts depending on the severity of the beta gene defect.

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Beta Thalassemia with Hb C

A genetic condition where an individual inherits one gene for hemoglobin C (Hb C) and one beta-thalassemia gene.

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How to test for Delta Beta Thalassemia?

Hemoglobin analysis can reveal the presence of elevated HbF and normal or reduced HbA2 in heterozygous individuals, while homozygous individuals lack both HbA and HbA2.

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How does Beta Thalassemia with Hb S affect red blood cells?

It affects the production of both abnormal hemoglobin (Hb S) and the synthesis of beta globin chains, leading to malformed red blood cells.

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Hemoglobin H Disease

A type of alpha-thalassemia where there's a 75% reduction in alpha-globin chains, leading to formation of Hemoglobin H (β4) tetramers. This causes severe anemia, RBC abnormalities, and potential hemolytic crises.

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Hemoglobin H (β4)

An abnormal hemoglobin molecule formed in Hemoglobin H disease, consisting of four beta-globin chains (β4). It has a reduced ability to bind oxygen and can cause severe anemia and hemolysis.

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Bart's Hydrops Fetalis Syndrome

The most severe form of alpha-thalassemia where there are no functioning alpha-globin genes, resulting in a complete absence of alpha chains. This leads to fetal hydrops (edema and ascites) due to severe anemia and often results in death in utero or shortly after birth.

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Hemoglobin Bart (γ4)

An abnormal hemoglobin molecule formed in Bart's Hydrops Fetalis Syndrome, consisting of four gamma-globin chains (γ4). It has a very high oxygen affinity, making it unable to release oxygen to tissues and resulting in severe fetal anemia.

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Target Cells in Alpha Thalassemia

Red blood cells with a central bullseye-like appearance often seen in alpha-thalassemia. They are caused by excess membrane and are associated with increased fragility and hemolysis.

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Study Notes

Thalassemia Overview

  • Thalassemia is a group of inherited blood disorders affecting hemoglobin genes.
  • It involves defective globin portion of the hemoglobin molecule.
  • Ineffective erythropoiesis results.
  • Characterized by decreased hemoglobin production leading to anemia of varying degrees.
  • An imbalance in globin chain production may cause hemolysis.
  • Two main types: alpha and beta thalassemia.

Normal Hemoglobin

  • Adult hemoglobin (HbA) has two alpha and two beta chains.
  • Hb A2 (α₂δ₂) accounts for 1.5-3.2%.
  • Hb F (α₂γ₂) accounts for 0.5-1%.
  • Fetus primarily has Hb F, while embryos mainly have Hb-Gower 1 (ζ₂ε₂) and Hb-Gower 2 (α₂ε₂). Hb Portland (ζ₂β₂) is another embryonic hemoglobin.

HbA Structure

  • Alpha globin chains consist of two genes from each parent.
  • Beta globin chains consist of one gene from each parent.

Fetal Hemoglobin (HbF)

  • Produced around 6 weeks of pregnancy.
  • Fetal levels remain high after birth, until roughly 2-4 months old.
  • Hb F binds oxygen more strongly, enabling the fetus to retrieve oxygen from the mother's bloodstream.
  • Levels decrease to normal adult levels (less than 1%) within the first year.
  • Beta thalassemias can delay this process, and cause higher than normal Hb F levels.

Homozygous vs Heterozygous

  • Humans have two copies (alleles) of each gene, one from each parent.
  • Heterozygous means one copy of a gene is mutated.
  • Homozygous means both copies of a gene are mutated.
  • In most hereditary disorders, homozygous genotypes are harmful as the protein products from both genes may fail to operate properly.
  • Heterozygous genotypes can be carriers but may result in milder disease forms in some conditions.

Homozygous vs Heterozygous (Continued)

  • If a trait is dominant (e.g., represented by letter B), its defective allele is represented by a lowercase b.
  • Homozygous dominant genotypes are represented as BB.
  • Homozygous recessive genotypes are represented as bb.
  • Heterozygous genotypes are represented as Bb.

Examples of Child Birth Genotypes

The probability of different genotypes for children born to parents with different genotypes is given in this section.

  • BB x BB = All children will be BB (normal).
  • BB x Bb = 50% BB, 50% Bb (half normal, half carrier).
  • Bb x Bb = 25% BB, 50% Bb, 25% bb (normal, carrier, affected).
  • BB x bb = All children will be Bb (carrier).
  • bb x bb = All children will be bb (affected).

Thalassemia (Continued)

  • Alpha thalassemia is caused by deletions of alpha globin genes.
  • Beta thalassemia is caused by mutations in beta globin genes.

Beta Thalassemia

  • Silent Carrier: Minimal decrease in beta chain production; no noticeable symptoms.
  • Beta Thalassemia Minor: Heterozygous; mild microcytic hypochromic anemia.
  • Beta Thalassemia Intermedia: Severity is between beta thalassemia minor and major.
  • Beta Thalassemia Major: Homozygous; severe anemia, usually transfusion-dependent, and may have organ damage.

Beta-Thalassemia Variants

  • Other forms include Beta Thalassemia with Hgb S (Sickle beta thalassemia), Beta Thalassemia with Hgb C (HbC/β+ Disease), and Beta Thalassemia with Hgb E. These involve different gene mutations or variants.

Alpha Thalassemia

  • Several types dependent on the number of affected genes
  • Silent carrier state - Affects one alpha gene.
  • Alpha thalassemia trait (Alpha Thalassemia Minor)- Affects two alpha genes.
  • Hemoglobin H Disease - Affects three alpha genes.
  • Bart's Hydrops Fetalis Syndrome - Affects all four alpha genes, often fatal.

Diagnostic Methods

  • Patient's individual and family history, along with ethnic background evaluation.
  • Physical examination (Pallor, Jaundice, Hepatosplenomegaly & skeletal abnormalities)
  • Laboratory investigations like complete blood count (CBC), blood smear, hemoglobin electrophoresis, biochemistry findings (iron studies and bilirubin), globin chain testing, and DNA analysis.

CBC with Differential (Additional Factors)

  • Decrease in hemoglobin, hematocrit, MCV, and MCH.
  • Microcytic, hypochromic pattern; Normal or elevated red cell count with normal RDW.
  • Marked target cells, elliptocytes, polychromasia, and NRBCs.
  • Elevated reticulocyte count, and/or Decreased osmotic fragility.

Hemoglobin Electrophoresis

  • Important for diagnosing and differentiating various forms of thalassemia.
  • Differentiates Hb A, Hb A2, and Hb F.
  • Detects abnormal hemoglobins and combinations of thalassemia and hemoglobinopathies.

Routine Chemistry Tests

  • Indirect bilirubin is elevated in thalassemia major and intermedia.
  • Iron status, iron binding capacity, and ferritin are crucial in differentiation from iron deficiency anemia.

Other Specialized Procedures

  • Globin Chain Testing: Determines the ratio of globin chains being produced.
  • DNA analysis: Determines the specific defect at the molecular DNA level.

Differential Diagnosis Table

  • A table differentiating microcytic hypochromic anemias, including different values for each condition.

Thank you

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Thalassemia PDF

Description

This quiz explores the complexities of thalassemia, a group of inherited blood disorders affecting hemoglobin production. Understand the differences between normal and fetal hemoglobin, as well as the genetic aspects of alpha and beta thalassemia. Test your knowledge on their structures and implications for health.

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