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MEH > Haemolytic Anaemias + Haemoglobinopathies > Flashcards

Haemolytic Anaemias + Haemoglobinopathies Flashcards

1
Q

What are the types of haemoglobin and their globin chain composition?

A

A - 2a/2B - prominent 6 months after birth
A2 - 2a/2delta
F/fetal - 2a/2gamma

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2
Q

What are haemoglobinopathies?

A

Genetic disorders which alter haemoglobin structure

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3
Q

Types of haemoglobinopathies

A
  • reduced/abscess expression of normal globin chains
    e.g. thalassaemia
  • abnormal globin chain variants with altered stability/ function
    e.g. sickle cell
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4
Q

Outline the types of thalassaemias + where they are most common

A

alpha:
- a globin gene expression affected
- common in far east populations

beta:
- B globin gene expression affected
- common in south Asian, Mediterranean + Middle East populations

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5
Q

Describe the alpha globin gene cluster

A

4 a globin genes - 2 per parents
On chromosome 16 (think 4x4=16)

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6
Q

Describe the beta globin gene cluster

A

2 B globin chains
On chromosome 11 (think 1+1=2 > 2 chains)

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7
Q

Alpha thalassaemia deletion 1
- disease
- severity
- info

A
  • disease: silent carrier state
  • severity: asymptomatic
  • info: carrier > no symptoms
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8
Q

Alpha thalassaemia deletion 2
- disease
- severity
- info

A
  • disease: a-thalassaemia trait
  • severity: minimal or none
  • info: microcytosis: smaller RBCs
    Hyprochromia: less pigmaneted RBCs
    Similar to B thalassaemia minor
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9
Q

Alpha thalassaemia deletion 3
- disease
- severity
- info

A
  • disease: haemoglobin H disease
  • severity: moderately severe
  • info: tetra of B-globin (HbH) formed
    Microcytic, hypochromic
    Heinz bodies , target cells
    Similar to B thalassaemia intermedia
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10
Q

Alpha thalassaemia deletion 4
- disease
- severity
- info

A
  • disease: Hydros fetalis
  • severity: severe > intrauterine death
  • info: tetramers of y globin (HbBart) formed
    Unable to deliver O2 to tissues - high affinity
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11
Q

Beta thalassaemia trait/minor
- severity
- genotype
- info

A
  • severity: asymptomatic with mild anaemia
  • genotype: heterozygous - 1 normal, 1 abnormal
    Bo/B or B+/B
  • info: microcytic + hypochromic RBCs
    Resembles a thalassaemia trait
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12
Q

Beta thalassaemia intermedia
- severity
- genotype

A
  • severity: severe anaemia
    But no regular blood transfusions
  • genotype: heterozygous - Bo/B
    Some mild homozygous - B+/B+
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13
Q

Beta thalassaemia major
- severity
- genotype
- info

A
  • severity: severe anaemia
    Regular blood transfusion needed
    Iron chelation needed
  • genotype: homozygous Bo/Bo or B+/B+
  • info: microcytic + hypochromic RBCs
    Abnormal skull bones
    Hepatosplemeglay due to etramedullary
    haemopoiesis
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14
Q

What are the consequences of thalassaemia

A
  • extramedullary haemopoiesis > hepatosplenomegaly
  • decreased O2 delivery > stimulation of EPO > more defective RBCs
  • decreased life expectancy
  • increased EPO > bone marrow expansion > skeletal deformities
  • iron overload due to repeated blood transfusions + excessive absorption of dietary iron due to ineffective haemopoiesis
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15
Q

Treatment of thalassaemia

A

Blood transfusion
Iron chelation
Folic acid - supports EPO
Immunisation
Stem cell transplant
Holistic care
Pre-conception counselling

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16
Q

Outline sickle cell disease

A
  • Autosomal recessive
  • Mutations of the B globin gene: glutamic acid > valine at position 6 (think SIXle cell anaemia)
    .
  • HbS form polymers > sickle shape
  • Repeated sickling cycle > irreversible sickle shape
  • Less flexible > occluded small blood vessels
  • More fragile > broken down > haemolytic anaemia
17
Q

Severe consequences of sickle cell anaemia

A

Stroke - form occlusions
Acute chest syndrome
Splenic atrophy
Kidney infarcts
Osteomyelitis

18
Q

Types of haemolysis and their location

A

intravascular - in blood vessels
extravascular - in spleen and wider RES

19
Q

Key lab findings in haemolytic anaemia

A

Increased reticulocytes
Increased bilirubin > gallstones + jaundice
Raised lactate dehydrogenase
Splenomegaly

20
Q

What is seen in a blood smear of a patient with severe thalassaemia?

A

Microcytic + hypochromic RBCs
Anisopoikilocytosis
Target cells
Nucleated red blood cells
Heinz bodies

21
Q

Types of haemolytic anaemia

A

Inherited - defective genes
Acquired - damage to cells

22
Q

Causes of inherited haemolytic anaemia

A
  • pyruvate kinase deficiency > less ATP
  • G6PDH deficiency > oxidative damage
  • haemoglobin defect e.g. sickle cell
  • membrane protein e..g hereditary spherocytosis
23
Q

Causes of acquired haemolytic anaemia

A
  • mechanical damage e.g microangiopathic haemolytic anaemia
  • antibody damage e.g. autoimmune haemolytic anaemia
  • oxidant damage
  • Heat damage e.g. severe burns
  • enzymatic damage e.g. snake venom
24
Q

Outline hereditary spherocytosis

A
  • Due to defect in ankyrin, spectrin, protein 4.2 or band 3 > disrupts membrane cytoskeletal interactions
  • spherical shape
  • less flexible + more easily damaged
25
Q

Outline hereditary eliptocytosis

A
  • Most commonly due to spectrin mutation
  • elliptical shape - oval
26
Q

Outline hereditary pyropoikilocytosis

A
  • Severe form of hereditary eliptocytosis
  • due to spectrin mutation
  • abnormal sensitivity of RBCs to heat
27
Q

Outline acquired haemolytic anaemia due to mechanical damage

A
  • Shear stress - defective heart valves
  • snagging on fibrin strands
  • Cause schistocytes
  • causes microangiopathic haemolytic anaemia
28
Q

Outline autoimmune haemolytic anaemias

A

Autoantibodies bind to RBC memebrane proteins
Spleen recognises as abnormal + removes them
Can result from infection + cancers of lymphoid system

29
Q

What are the 4 types of a thalassaemia?

A

Silent carrier state
a thalassaemia trait
HbH disease
Hydrophobic fetalis

30
Q

Types of B thalassaemia

A

Trait/minor
Intermedia
Major

31
Q

What does Bo and B+ mean?

A

Bo - total absence
B+ - reduction of globin production

32
Q

What does band 3 do?

A
  • Binds to ankyrin + protein 4.2 to link membrane + cytoskeleton
  • facilitates Cl- + HCO3- exchange
33
Q

What is protein 4.2?

A
  • ATP binding protein
  • regulates association of band 3 with ankyrin
34
Q

What is ankyrin?

A

‘Anchoring’
Links protein to spectrin-actin cytoskeleton

35
Q

What is spectrin?

A

Links plasma membrane to actin cytoskeleton

36
Q

What is caused by a mutation in spectrin

A
  • Hereditary spherocytosis: mutations causes less flexibility > spherocytes
  • Hereditary ellipocytosis
37
Q

When does B thalassaemia major manifest?
Why?

A

6-9 months after birth
Hbf > HbA

38
Q

What is the inheritance of sickle cell disease?

A

Autosomal recessive

39
Q

Outline the process of sickle cell disease

A
  • HbS form polymers > sickle shape
  • Repeated sickling cycle > irreversible sickle shape

MEH (23 decks)

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