Introduction to Abnormal Haemoglobins
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Questions and Answers

What genotype is associated with β-thalassaemia minor?

  • β+/β0
  • β/β+ (correct)
  • β+/β+
  • β0/β0

Which clinical feature is least likely to be seen in a patient with α-thalassaemia carrier?

  • Splenomegaly
  • Asymptomatic
  • Hb H disease
  • Moderate anaemia (correct)

Which description accurately reflects the most severe form of β-thalassaemia?

  • Normal growth and development
  • Asymptomatic with no significant findings
  • Mild anaemia with no organomegaly
  • Severe anaemia with growth retardation (correct)

Which statement accurately describes the consequences of α4 deletion?

<p>Results in hydrops and is incompatible with life (B)</p> Signup and view all the answers

What is the main pathological characteristic of β-thalassaemia intermedia?

<p>Moderate anaemia with possible hepatosplenomegaly (A)</p> Signup and view all the answers

Which condition is described as being incompatible with life due to α-thalassaemia?

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

Which statement correctly describes the effect of pathological hemoglobin variants?

<p>They can affect oxygen carrying capacity and red cell lifespan. (B)</p> Signup and view all the answers

What is the common clinical feature of β-thalassaemia major?

<p>Severe anaemia and hepatosplenomegaly (A)</p> Signup and view all the answers

What is the expected clinical feature of HbH disease?

<p>Mild to moderate hemolytic anaemia (A)</p> Signup and view all the answers

At what point in severity do thalassaemias become incompatible with life?

<p>With specific mutations causing severe imbalances (C)</p> Signup and view all the answers

What is the primary characteristic that differentiates a quantitative defect from a qualitative defect in hemoglobin?

<p>Qualitative defects involve structural variants of globin chains. (C)</p> Signup and view all the answers

Which of the following is not a variant type associated with qualitative structural defects in hemoglobin?

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

What distinguishes α-thalassaemia from α-thalassaemia carrier status?

<p>Both carriers and α-thalassaemia patients are generally asymptomatic. (B)</p> Signup and view all the answers

Which statement correctly describes the relationship between α-thalassaemia and microcytic anemia?

<p>Mild microcytic anemia can occur in α-thalassemia minor. (C)</p> Signup and view all the answers

In β-thalassaemia, which characteristic is true regarding the synthesis of globin chains?

<p>β-thalassaemia causes a reduced synthesis of β-globin chains. (B)</p> Signup and view all the answers

What is a notable symptom of HbH disease?

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

Which of the following correctly relates to hydrops fetalis in α-thalassemia?

<p>Hydrops fetalis is an advanced manifestation of severe α-thalassemia. (C)</p> Signup and view all the answers

Which amino acid substitution characterizes HbS variant?

<p>Glu-6-Val (C)</p> Signup and view all the answers

Which of the following traits is NOT associated with α-thalassaemia?

<p>Carriers exhibit severe clinical symptoms. (A)</p> Signup and view all the answers

What is the primary consequence of qualitative structural defects in hemoglobin?

<p>Altered function or stability of the hemoglobin molecules. (C)</p> Signup and view all the answers

Flashcards

Haemoglobinopathies

Haemoglobinopathies are a group of inherited blood disorders that affect the production of hemoglobin, the protein in red blood cells that carries oxygen. They are broadly divided into two categories: Quantitative defects, affecting the amount of hemoglobin produced, and qualitative defects, affecting the quality of hemoglobin.

Thalassemias

Thalassemias are genetic disorders characterized by reduced synthesis of one or more globin chains, leading to a deficiency in normal hemoglobin production. They are classified as either α-thalassemia or β-thalassemia, based on which globin chain is affected.

α-thalassemia

α-thalassemia is a group of disorders caused by a deficiency in the production of alpha globin chains. These disorders can range from asymptomatic carriers to severe anemia with complications.

β-thalassemia

β-thalassemia is a group of disorders caused by a deficiency in the production of beta globin chains. This can range from mild anemia to severe disease with complications.

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Structural Hemoglobin Variants

Structural hemoglobin variants are caused by mutations in the globin genes, resulting in abnormal hemoglobin molecules with altered properties.

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Hemoglobin S (HbS)

HbS (sickle cell hemoglobin) is a structural hemoglobin variant caused by a single amino acid substitution in the beta globin chain. This leads to the formation of rigid, sickle-shaped red blood cells that can block blood flow.

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Hemoglobin C (HbC)

HbC is a structural hemoglobin variant caused by a different amino acid substitution in the beta globin chain. It causes a milder form of anemia than sickle cell anemia.

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Hemoglobin D (HbD)

HbD is a structural hemoglobin variant caused by yet another amino acid substitution in the beta globin chain. It causes a mild form of anemia, often presenting with enlargement of the spleen.

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Hemoglobin E (HbE)

HbE is a structural hemoglobin variant caused by a specific amino acid substitution in the beta globin chain. It is particularly prevalent in Southeast Asia and is related to a mild form of anemia.

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HbH disease

HbH disease is a severe form of α-thalassemia, characterized by production of a tetramer of four beta globin chains, leading to a marked deficit in functional hemoglobin. This results in severe anemia, enlarged spleen (splenomegaly), and complications like hydrops fetalis in severe cases.

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Hemoglobinopathy

A genetic condition caused by mutations in the genes that control the production of hemoglobin, the molecule in red blood cells that carries oxygen.

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Carrier (α or β thalassaemia)

An individual carrying one copy of a mutated gene for alpha or beta globin, often showing minimal or no symptoms.

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Thalassaemia Intermedia

A milder form of α or β thalassaemia, characterized by a mild reduction in hemoglobin levels and possible splenomegaly.

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Thalassaemia Major

The most severe form of α or β thalassaemia, leading to severe anemia, hepatosplenomegaly, and growth retardation.

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Hydrops fetalis (α-thalassaemia)

A fatal condition resulting from a complete lack of alpha globin chains, leading to severe anemia and hydrops fetalis.

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Incompatible with life

A situation in which a genetic trait is not expressed due to the absence of a specific gene product.

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Study Notes

Introduction to Abnormal Heritable Haemoglobins

  • Haemoglobinopathies are abnormal haemoglobins.
  • Many haemoglobin variants are clinically silent.
  • Pathological variants affect oxygen-carrying capacity, haemoglobin solubility, or red blood cell lifespan.
  • Thalassaemias involve globin chain imbalances.

Learning Objectives

  • Differentiate between quantitative and qualitative structural haemoglobin defects.
  • Compare and contrast α and β thalassaemia subtypes.

Heritable Haemoglobin Variants

  • Quantitative defects (amount) involve reduced synthesis of normal globin chains (thalassaemias).
  • Qualitative defects (quality) involve structural variants in haemoglobin.
    • Examples: HbS, HbC, HbD, HbE, Glu-6-Val, Glu-6-Lys, Glu-121-Gln, Glu-26-Lys

Alpha-Thalassaemia

  • Normal: α α α α
  • Carrier: α α α - (asymptomatic, no symptoms)
  • α-thal minor: α α - - (mild microcytic anaemia)
  • HbH disease: α - - - or α - - - (Symptomatic, microcytic anaemia, splenomegaly)
  • Hydrops foetalis: - - - - (Incompatible with life)

Beta-Thalassaemia

  • Normal: β β
  • Minor: β β (asymptomatic, no symptoms)
  • Intermedia: β β, β+/β0 (Mild anaemia, splenomegaly)
  • Major: β0/β0 (severe anaemia, hepatosplenomegaly, growth retardation).

Thalassaemias

  • β Thalassaemia (Genotype/Clinical features)
    • Carrier/trait (β+/β+, β/0): Normal to mild anaemia, no organomegaly
    • Intermedia (β+/β+, β+/β0): Mild anaemia, hepatosplenomegaly
    • Major (β0/β0): severe anaemia, hepatosplenomegaly, growth retardation
  • α Thalassaemia (Genotype/Clinical features)
    • α-thal carrier (αα/-α, -α/-α or αα/--): Asymptomatic
    • HbH disease (-α/--): moderate to severe hemolytic anemia, moderate ineffective erythropoiesis, splenomegaly, variable bone changes.
    • Hb Barts/hydrops foetalis (--/--): incompatible with life

Consequences of α4 Deletion

  • Decreased Hb synthesis.
  • Most Hb is Hb Bart's.
  • Tissue hypoxia.
  • Maternal complications like preeclampsia, hypertension, and retained placenta.
  • Heart failure, extra-medullary erythropoiesis, and organogenesis issues.

Summary

  • Haemoglobinopathy describes abnormal haemoglobins.
  • Thalassaemia involves globin chain imbalances.
  • Clinical severity varies from clinically silent to incompatible with life.

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Introduction to Abnormal Heritable Haemoglobins PDF

Description

Explore the fascinating world of haemoglobinopathies in this quiz. Understand how different variants affect oxygen transport and the implications of thalassaemias. Test your knowledge on the structural defects and the classifications of these abnormal haemoglobins.

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