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notes to flashcards year 2 - MCD > Haemoglobin and Thalassaemia > Flashcards

Haemoglobin and Thalassaemia Flashcards

1
Q

when does the synthesis of Hb begin?

A
  • in RBC pro-erythroblast stage
  • 65% in erythroblast stage
  • 35% in reticulocyte stage
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2
Q

where is haem/globin synthesized?

A

Haem - in mitochondria

Globin - in ribosomes

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3
Q

describe the synthesis of haem?

A
  • transferrin transports ferrous to RBC
  • or ferrous is liberated from ferritin
  • delta-ALA undergoes few moderations outside mitcocondria
  • passes back in as proto-porphyrin
  • proto-porphyrin –> haem
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4
Q

describe the synthesis of globin

A

amino acids are used in ribosomes to create globin chains

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5
Q

what proteins are haem contained within?

A
  • myoglobin

- cytochromes

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6
Q

what is haem?

A
  • combination of a proto-porphyrin ring

- and central ferrous

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7
Q

how may functional globin chains are there

A

8 arranged in 2 clusters

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8
Q

describe the beta cluster

A

beta, gamma, delta, epsilon

encoded on Chr 11, p-arm

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9
Q

describe alpha cluster

A

alpha, zeta

encoded on Chr 16, p-arm

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10
Q

describe levels of alpha (globin gene expression/switching)

A

made relatively early

stays high throughout

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11
Q

describe levels of beta (globin gene expression/switching)

A

equal and opposite to gamma

becomes dominant after birth

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12
Q

describe levels of gamma (globin gene expression/switching)

A
  • equal and opposite to beta

- becomes dominate pre natal

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13
Q

describe levels of delta

A
  • production begins mid-natal

- remains low forever

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14
Q

describe levels of epsilon and zeta

A
  • equal and opposite to alpha

- levels drop to 0 after 8 weeks

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15
Q

describe the Hb abundances

A

HbA (alpha 2, beta 2) - 96-98%
HbA2 (alpha 2, delta 2) - 1.5-3.2%
HbF (alpha 2, gamma 2) - 0.5-0.8%

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16
Q

describe the primary structure of globin

A

alpha (141aa)

non-alpha globins (146aa)

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17
Q

describe the secondary structure of globin

A

75% of alpha and beta chains show helical arrangement

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18
Q

describe the tertiary globin structure

A
  • approx sphere with a hydrophillic surface and a hydrophobic core
  • contains a haem pocket
19
Q

when does Hb have the highest affinity for oxygen?

A
  • when binding is loose
  • cooperativity
  • more oxygen means greater binding of oxygen
  • 2,3-DPG made by muscle cells to inc. dissociation of oxygen
20
Q

what does the sigmoid shape of ODC allow?

A

greater unloading across a range of low pressures

21
Q

what does the position of ODC depend on?

A
  • 2,3-DPG conc
  • pH
  • Co2 conc
  • structure of Hb
22
Q

what would cause a right shift?

A
  • high H+
  • high 2,3-DPG
  • high CO2
  • HbS
23
Q

what are haemoglobinopathies?

A
  • genetic disorder characterized by a defect of globin chain synthesis
24
Q

how is thalassaemia classified?

A
  • globin type affected
  • clinical severity: minor or trait, intermedia, major
  • 4 alpha clusters in total but only 2 beta
25
Q

what is beta-thalassaemia?

A

autosomal recessive

deletion or mutation in beta-globin chains

26
Q

what is beta 0?

A

deletion of one beta globin encoding gene

27
Q

what is beta +?

A

mutation of one beta globin encoding gene

28
Q

what are the lab diagnosis characteristics of thalassaemia?

A
  • FBC: microcytic hypochromia, inc. RBCs

- film: target cells, poikilocytosis but no anisocytosis

29
Q

what would you see in the levels of Hb in alpha thal?

A

normal HBA2 and HbF

30
Q

what would you see in the levels of Hb in beta thal?

A

raised HbA2 and HbF

31
Q

what is beta-thalassaemia trait?

A
  • carrier trait

- often asymptomatic

32
Q

how is beta thala trait diagnosed?

A
  • by blood film
  • shows macrocytic blood cells
  • raised HbA2 and HbF
33
Q

what is beta thalassaemia major?

A
  • carry 2 abnormal copies of beta-globin gene
  • severe anaemia
  • require regular blood transfusions
  • clinical representation after 4-6 months
34
Q

what would you see on a blood film?

A
  • anaemia
  • irregularly contracted cells
  • hypochromic cells
  • alpha chain precipitates
  • nucleated RBCs
35
Q

what is the clinical representation?

A
  • severe anaemia after 4 months
  • hepatosplenomegaly
  • bone marrow
  • erythroid hyperplasia
  • hypochromia, poikilocytosis
  • extra medullary haematopoiesis
36
Q

what are the clinical features?

A
  • chronic fatigue
  • failure to thrive
  • jaundice
  • late puberty
  • splenomegaly
  • skeletal deformity
  • iron overload
37
Q

what are the complications?

A
  • cholelithiasis
  • biliary sepsis
  • cardiac/live failure
  • endocrinopathies
38
Q

what is the treatment?

A
  • regular blood transfusions
  • iron chelation therapy
  • splenectomy
  • supportive medical care
39
Q

what are patients who have high iron content more prone to?

A
  • yersinia infection

- other gram -ve infections

40
Q

when is iron chelation therapy started?

A

after 10-12 transfusions
when serum ferritin >1000mcg/L
audiology and opthalmology screening needed before starting

41
Q

what are the 3 forms of iron chelating drugs?

A
  • DFO
  • Deferiprone
  • Deferasirox
42
Q

how do you monitor iron overload?

A
  • serum levels of ferritin
  • liver biopsy
  • MRI T2 cardiac and hepatic
  • ferriscan
43
Q

what complication can beta thal be coinherited with?

A
  • sickle beta thalassaemia

- HbE beta thalassaemia

44
Q

what is alpha thalassaemia?

A
  • deletion/mutation in alpha globin genes
  • affected both foetus and adults –> alpha is in ALL globin variants
  • severity depends on no. of chains affected

notes to flashcards year 2 - MCD (24 decks)

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