38 Questions
What is the main characteristic of hemoglobin disorders?
Qualitative defects resulting from single amino acid substitutions
What is the effect of the mutation in sickle cell hemoglobinopathy?
Affects the stability of the Hb molecule during hypoxia
What is the result of homozygous occurrence of the sickle gene?
Severe, chronic hemolytic anemia
What is the characteristic of thalassemias?
Quantitative defects in globin chain synthesis
What is the effect of the substitution of glutamic acid with valine in sickle cell hemoglobinopathy?
Affects the stability of the Hb molecule during hypoxia
What is the result of heterozygous occurrence of the sickle gene?
Benign clinical course with mild anemia and hemolysis
What is the group of gene mutations that interfere with the switching of fetal to adult Hb production known as?
Hereditary persistence of high fetal hemoglobin (HPFH)
What percentage of HbS is found in the red cells of individuals with sickle cell anemia?
90-100%
What is the primary characteristic of thalassemia syndromes?
Hypochromic anemia caused by deficient synthesis of one or more polypeptide chains of hemoglobin
Which chromosomes are involved in the production of hemoglobin?
Chromosomes 11 and 16
What is the commonest type of β-thalassemia?
β-thalassemia trait
What is the net result of the hemolytic component of the disease?
Removal of inclusions by the monocyte-macrophage system
What is the result of the free α chains forming α-globin tetramers?
Unstable α-globin tetramers leading to intraerythrocytic inclusion bodies
At what age is the onset of the disease usually seen?
Second half of the first year
What is a characteristic of α-thalassemia?
Reduced synthesis or absent synthesis of α-globin chains
What is the characteristic feature of blood smear in chronic hemolytic anemia?
Target cells and nucleated cells, extreme anisocytosis
What is the genotype of a person with β-thalassemia minor?
Heterozygous
What is the risk of thalassemia major when both parents have thalassemia trait?
25%
What is a common manifestation of hemosiderosis?
Abnormal facies
What is the effect of the disease on erythropoiesis?
Erythropoiesis is ineffective
What is the minimum volume of packed RBCs required per year?
240 ml/kg/year
What is the range of HbA2 in β-thalassemia trait?
3.4-7%
What is a common feature of chronic hemolytic anemia?
All of the above
What percentage of HbF is raised in chronic hemolytic anemia?
More than 90%
Why should splenectomy be delayed until after 5-6 years of age?
To avoid overwhelming infection in young children with immature immune system
What is the goal of blood transfusion in chronic hemolytic anemia?
To maintain Hb above 9.5 g/dl
What is a characteristic of red blood cells in β-thalassemia trait?
Microcytic and hypochromic
What is the most effective treatment for chronic hemolytic anemia?
Bone marrow transplantation
What is the term for the loss of all marrow elements leading to anemia, leukopenia, and thrombocytopenia?
Pancytopenia
What is the term for a marked decrease or absence of blood-forming elements in the bone marrow?
Aplastic anemia
What is the characteristic feature of Fanconi anemia?
Short stature, skin hyperpigmentation, and skeletal abnormalities
What is the primary goal of general care in pancytopenia?
To isolate the patient and provide fresh air
What is a common complication of pancytopenia?
All of the above
What is the only curative therapy for pancytopenia?
Bone marrow transplantation
What is a characteristic laboratory finding in pancytopenia?
Low HB level and RBCs
What is a possible treatment for pancytopenia if bone marrow transplantation is not available?
All of the above
What is a characteristic feature of acquired pancytopenia?
Manifestation of the underlying cause
What is a common cause of acquired pancytopenia?
Drugs and chemicals
Study Notes
Hemoglobin Disorders
- Hemoglobin disorders are qualitative defects resulting from single amino acid substitution in the alpha or beta chains of adult hemoglobin.
- These defects affect the stability of the Hb molecule and alter its oxygen affinity.
Structural Hemoglobin Variants
- These are qualitative defects that result from single amino acid substitution in the alpha or beta chains of adult hemoglobin.
- Examples include sickle cell hemoglobinopathy.
Sickle Cell Hemoglobinopathy
- Characterized by a structural defect of β chains of hemoglobin where glutamic acid in position number 6 is replaced by valine (α2-β2 6 val).
- This minor defect affects the stability of the Hb molecule during hypoxia, distorting the red cell membrane and forming sickled cells.
Sickle Cell Anemia
- Homozygous occurrence of the sickle gene with two abnormal genes results in severe, chronic hemolytic anemia.
- Heterozygous occurrence of the sickle gene (one abnormal gene) has red cells containing 35-45% Hb S, usually with a benign clinical course with mild anemia and hemolysis.
Thalassemias
- A heterogeneous group of inherited disorders characterized by hypochromic anemia caused by deficient synthesis of one or more of the polypeptide chains of human Hb.
- Two hemoglobin gene clusters are involved in the production of Hb and are located on chromosomes 11 and 16.
β-Thalassemia
- Decrease in the formation of β chains (HbA) with the formation of γ chains (HbF) and δ chains (HbA2) to compensate for the deficiency of adult Hb.
- Four grades of β thalassemia:
- Silent carrier (asymptomatic)
- β-thalassemia trait (mild anemia)
- β-thalassemia intermedia (moderate anemia)
- β-thalassemia major (hydrops fetalis)
α-Thalassemia
- Disorders caused by reduced synthesis or absent synthesis of α globin chains.
- Four clinical types:
- Hemoglobin H disease
- β-thalassemia minor
- α-thalassemia trait
- α-thalassemia major
Learn about the inherited disorders of thalassemias, characterized by hypochromic anemia and deficient synthesis of hemoglobin polypeptide chains.
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