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Haematology > Haemoglobinopathies > Flashcards

Haemoglobinopathies Flashcards

1
Q

What are Heinz bodies?

A

Oxidised, denatured haemoglobin

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2
Q

What are thalassemias and haemoglobinopathies?

A

Thalassemias: decreased synthesis of wild-type haemoglobin.
Haemoglobinopathies: Synthesis of mutant haemoglobin chains (e.g sickle cell anaemia)

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3
Q

What happens to patients with sickle cell anaemia?

A
  • Patients suffer from severe anaemia and pain
  • Suffer from crises: obstruction of blood vessels by sickled RBCs causing ischaemic injuries.
  • Crises can be vast-occlusive, visceral, aplastic or haemolytic.
  • Damage to organs such as liver, kidney, heart and spleen.
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4
Q

Biochemical features of sickle cell anaemia.

A

HbS has an isoelectric point higher than HbA.

HbS has an amino acid substitution in the beta chain: substitution of a valine for a glutamic acid.

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5
Q

Sickle cell features.

A
  • HbS sticks together to form long rods inside the red blood cells making them rigid and sickle-shaped. This can cause blood vessel blockage, stopping O2 from getting to where it is needed.
  • HbS is insoluble and forms crystals when exposed to low O2 tension.
  • Lack of O2 is what causes shape change.
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6
Q

Types of sickle cell crises and what they do

A

Vaso occlusive:
-sickle cells adhere to neutrophils and endothelial cells.
Visceral
-sickling within organs and pooling of blood
Haemolytic
-Increase rate of haemolysis, fall in Hb

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7
Q

Diagnosis of Sickle cell anaemia

A
  • Low haemoglobin (6-9g/dL)
  • Sickle cells and target cells in blood
  • Tests for sickling are positive
  • Elecrophoresis- no HbA is detected, HbF varies between 5-15%.
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8
Q

Sickle cell testing during pregnancy

A
  • Samples obtained by chorionic villus biopsy
  • Amniotic fluids can be used
  • PCR used to amplify DNA
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9
Q

Treatment of sickle cell anaemia

A
  • Folic acid
  • Vaccination
  • Treat crises by rest, hydration
  • Blood transfusions
  • Hydroxyurea
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10
Q

Sickle cell trait features

A

One sickle cell Hb gene, one normal gene
Carrier has enough sufficient normal Hb to keep cells flexible
No anaemia
Red cells look normal

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11
Q

Other types of haemoglobin and some features

A

HbE: mild microcytic, hypo chromic anaemia
HbD: homozygotes have mild hypochromic anaemia
HbC: form rhomboidal crystals, mild haemolytic anaemia with target cell formation and microspherocytes.

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12
Q

What is the difference between haemoglobin H disease and Hydrops fetalis?

A

Haemoglobin H disease has 1 alpha allele and 3 missing alleles- it is a double heterozygote. Hydrops fetalis does not have ANY alpha alleles- it is a homozygote.

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13
Q

What are the alpha thalassemia traits?

A

alpha+ homozygotes (a-/a-) or alpha0 heterozygotes (aa/–)

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14
Q

What are the features and laboratory findings of haemoglobin H disease?

A
  • Moderate to severe anaemia
  • Hepatosplenomegaly
  • Microcytosis
  • Hypochromasia
  • Fragmented RBCs
  • Poikilocytosis
  • Polychromasia
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15
Q

Features and laboratory findings of Hydrops fetalis.

A
  • No functionally normal haemoglobin
  • Hb Barts (gamma x4) and HbH (beta x4) are synthesised
  • Microcytosis
  • Hypochromasia
  • Fragmented RBCs
  • Poikilocytosis
  • Numerous nucleated cells
  • Almost always fatal
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16
Q

What causes alpha thalassemia?

A

Impaired synthesis of alpha globin chains resulting in accumulation of other globin chains.
The unpaired globin chains are unstable and form insoluble aggregates with the cell.
Alpha genes are deleted not mutated.

17
Q

Features of beta thalassemia major

A
  • Decreased synthesis of beta chains
  • Result from point mutations in the beta globin gene.
  • Excess alpha genes precipitate in erythroblasts and mature RBCs causing severe ineffective erythropoiesis and haemolytic. The greater the excess the more severe the anaemia.
18
Q

Clinical features of beta thalassemia major

A
  • Severe anaemia
  • Hepatosplenomegaly
  • Bones expand (maxilla, frontal and parietal bones)
  • Secondary iron overload
  • Low serum hepcidin levels
19
Q

What is beta thalassemia intermedia caused by?

A
  • Homozygous beta thalassemia where HbF is synthesised in greater amounts than normal.
  • Mild defects in beta chain synthesis.
20
Q

Clinical features of beta thalassemia intermedia

A
  • Anemia is moderately severe
  • Hb is 7-10g/dL
  • Bone abnormalities
  • Enlarged spleen or liver
  • Extramedullary erythropoiesis
  • Iron overload (due to inc. absorption)
21
Q

Techniques and features used to diagnose beta thalassemia major.

A
  • Severe hypochromic, microcytic anaemia
  • Raised reticulocyte percentage
  • Electrophoresis to detect levels of HbA and HbF
  • DNA analysis to detect genetic mutations
  • Iron overload tests- serum ferritin most common
22
Q

Thalassemia treatments

A

Blood transfusions
-2-3 units of blood every 4-6 weeks

Iron chelation therapy

  • Iron overload is a consequence of regular transfusions
  • Most common drug is DEFEROXAMINE (iron excreted in urine), DEFERIPRONE (orally 3x a day, removes cardiac iron), DEFERASIROX (new, once a day, faecal iron excretion)

Folic acid
Splenectomy
Bone marrow transplants

Haematology (7 decks)

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