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MELS302 > Hb > Flashcards

Hb Flashcards

1
Q

What determines the net negative charge of Hb

A

Amino acid sequence variation

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2
Q

Globin chain loops to form a haem pocket, what is in hers

A

A protoporphyrin ring and Fe2+
Oxygen binds here and makes blood red

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3
Q

Where is haem made

A

In the cytoplasm and mitochondria of RBC precursors

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4
Q

What are porphyrias

A

Group of disorders for Haem abnormalities

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5
Q

Globin chains are made on what molecule

A

Ribosomes, controlled by 6 genes

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6
Q

What is made on chromosome 16

A

2 alpha genes
1 zeta gene

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7
Q

What is made on chromosome 11

A

2 gamma
2 bet
1 E

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8
Q

When does the Hb switch happen

A

3 months beta replaces gamma

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9
Q

Adult Hb

A

Most HbA

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10
Q

What chains make up HbF

A

2 alpha
2 gamma

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11
Q

Do you have Hb adult at birth

A

Yes but not in utero

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12
Q

What is Hb assembled

A

Released from ribosomes
Globin chain and haem pair off
Heterodimer = alpha chain + non alpha
2 combine heterodimer = tetramer which is Hb
Last step is spontaneous

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13
Q

What can decrease RBC survival in Hb assembly

A

excess components clumping like iron, unpaired chains, ring

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14
Q

What is a quantitative haemoglobin disorder

A

Reduced rate of synthesis of Globin chains
Thalassaemia

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15
Q

Qualitative Hb disorders

A

Synthesis of an abnormal haemoglobin
Haemolysis, cyanosis, familial polycythemia, HbM

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16
Q

Can Thalassaemia coexist with other Haemoglobinopathies

A

Yes

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17
Q

What is Thalassaemia

A

Mutation or deletion causing the production of either the alpha or beta chain to be reduced, can result in the accumulation of the non effected chain which damages RBC
microcytic hypochromic

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18
Q

What gene defects cause Thalassaemia

A

mRNA processing errors
Deletion of Globin genes
Translational errors from a frame shift /mis sense

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19
Q

How many genes does the alpha Globin have

A

4

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20
Q

What is the silent carrier state - alpha

A

1 gene deletion
(-a/aa)
1-2% HbH Bart made at birth
Genetical analysis
Near normal A:B ratio

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21
Q

What is alpha Thalassaemia minor

A

2 gene deletion
Homozygous : (-a/-a)
Heterozygous: (- -/aa)
Near normal ratio
5-15% HbH Bart

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22
Q

How does alpha Thalassaemia minor present

A

Asymptomatic
Mild microcytic hypochromic anaemia

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23
Q

What is HbH disease - ratio

A

3 gene deletion (- -/-a)
a:B ratio is disrupted
Beta chains excess make unstable tetramers/HbH

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24
Q

How does HbH present - blood film

A

Mild/moderate chronic haemolytic anaemia
Bite cells
Target cells
Poikilocytosis

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25
Q

Bone marrow changes in HbH disease

A

Erythroid hyperplasia
Splenomegaly

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26
Q

Is Hbh affected by a haemolytic crisis

A

Yes
Infection, oxidative drugs, pregnancy

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27
Q

What is Hb Bart disease

A

4 gene alpha deletion
No alpha chains made so no HbF/Gower2/HbA

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28
Q

What are Hb Bart

A

An unstable tetramer made from excess gamma chains
High affinity for oxygen so doesn’t deliver

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29
Q

Outcome of Hb Bart

A

Did in utero or hours after birth
Mother at increased risk of toxemia and post partum haemorrhage

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30
Q

How is Hb Bart detected

A

DNA analysis of chorionic villus, amniotic fluid, cord blood

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31
Q

Hb Bart blood film

A

Severe microcytosis hypochromic anaemia
Basophilic stippling
Dysplastic NRBCs

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32
Q

What is seen in hydrops fetalis syndrome

A

Anaemia
Extramedullary haemopoiesis
Organ failure
Total body odema

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33
Q

How do Hb H appear on film

A

Golf ball inclusion bodies
Retic stain

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34
Q

How do HbH affect RBC

A

They are easily oxidised and they precipitate and denature distorting RBC so they get stuck in the spleen and so survival decrease

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35
Q

How to diagnose Thalassaemia

A

Clinical examination
Family history - ethnicity
Blood film
Hb electrophoresis- acid and alkaline
PCR to find specific mutation

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36
Q

FBC for Thalassaemia

A

Increased RBC count
Low MCV
Low RDW
Reticulocytosis

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37
Q

If a co existing Haemoglobinopathy is suspected what test do you do

A

HPLC or Hb electrophoresis

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38
Q

What happens in beta/alpha Thalassaemia in electrophoresis

A

Beta - low or absent HbA, increase HbF/A2 varies
Alpha - Hbh present maybe Bart, low Hb A/A2/F

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39
Q

What are haemoglobinopathies

A

Gene defect causing a structural defect in one of the Globin genes

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40
Q

What is the slient carrier state beta

A

Small decrease in production of one Beta gene
Asymptomatic nothing on blood film

41
Q

What is beta Thalassaemia minor

A

Partial decrease in one or full in one beta gene

42
Q

Beta Thalassaemia minor blood
Film

A

Mild microcytic hypochromic anaemia
Asymptomatic
Target cells
Basophilic stippling
Poikilocytosis
Elliptocytes

43
Q

How do the other Hb act in beta Thalassaemia minor

A

Decreased HbA, increases HbF and maybe A2

44
Q

Why can NRBCs be problematic for FBCs in analysers

A

NRBC resist lysis and can be counted as a lymphocyte
Showing a false WBC increase

45
Q

Beta Thalassaemia intermedia blood film

A

Lots of NRBC
target cells, more severe anaemia than B Thalassaemia minor
Basophilic stippling
Teardrops
Elliptocytes
Poikilocytes

46
Q

Does beta Thalassaemia need blood transfusions

A

No even though it’s more severe
Count get splenectomy

47
Q

When does a total WBC corrected count need to be done

A

When more than 5 NRBC per 100 WBC

48
Q

When does beta Thalassaemia major present

A

When the switch to HbA fail at 3-6 months

49
Q

Beta Thalassaemia major blood film

A

Marked microcytic hypochromic anaemia
TARGET CELLS
tear drops
Elliptocytes
Fragments
Poikilocytosis, anisocytosis
Erythroblasts
Basophilic stippling
Alpha inclusion bodies

50
Q

What happens overall to RBC in Beta Thalassaemia major

A

Haemolysis
Ineffective erythropoiesis
HbA can be absent

51
Q

Genotype of beta Thalassaemia major

A

Both genes half missing
Both genes missing
1 full gene missing, and other half gene missing

52
Q

Clinical features of beta Thalassaemia major

A

Hepatosplenomegaly
Extramedullary erythropoiesis causes marrow expansion = skeletal changes and growth retardation
Infections
Iron overload

53
Q

Beta Thalassaemia major treatment and cure

A

Treatment - blood transfusions, splenectomy (wait until 7-8years), iron chelation therapy
Cure - bone marrow transplant, gene therapy

54
Q

Heterozygous sickle cell blood film

A

Mild
No anaemia

55
Q

Heterozygous sickle cell found where

A

20-40% frequency in Africa
Protection against malaria

56
Q

What leads to a heterozygous sickle cell crisis

A

Sickle cells will precipitate at low oxygen pressure
From severe fever, hypoxia, high altitude, plane, lung infections

57
Q

What does the amino acid substitution cause in the sickle cells

A

Position 6 Glu to Val
Means the tertiary structure now has a hydrophobic group exposed leading them to clump together and get distorted

58
Q

Order of what deoxygenation does to sickle cells (allosteric change) - how are sickle cells formed

A

Polymer forms
Ca influx and water and K leaves
Cell is dehydrated
Precipitation of polymers to form sickle cells

59
Q

What happens in the body with sickle cells

A

Increase in blood viscosity
Decrease flow
Increase hypoxia and lower pH promotes more sickling
Haemolysis and occlusion
Anaemia
Infarction and inflammation

60
Q

Sickle cell crisis leads too

A

Aplasia (after infection parvovirus)
Acute chest syndrome
Visceral sequestration
Vasooclusion causing infarctions in eyes, lungs, bones etc

61
Q

Where does visceral sequestration happen in a sickle cell crisis

A

Spleen, liver, lungs in infants and children

62
Q

What is acute chest syndrome - sickle cell crisis

A

Vasooclusive crises of pulmonary vascular
Associated with fever/chest pain/pulmonary infiltrates

63
Q

What triggers vasooclusion which causes infarcts during a sickle cell crisis

A

Hypoxia, acidosis (low pH encourages sickling), dehydration, fever, cold temp

64
Q

Where do sickle cell infarctions happen

A

Bones
Lungs
Liver
Penis
Eyes
CNS
UT
Spleen

65
Q

Sickle cell blood film

A

Chronic haemolytic anaemia
Normocytic normochromic anaemia
Polychromatic, poikilocytosis, anisocytosis
Target cells
Sickle cells
Reticulocytosis unless aplastic

66
Q

If spleen is infarcts in sickle cell what does the blood film look like

A

Marked poikilocytosis
NRBC
Basophilic stippling
Spherocytosis
Pappenheimer bodies
Howell jolly bodies

67
Q

Treatment for sickle cell

A

Immunisation for bacterial infections like strep pneumoniae
Childhood prophylactic penicillin
Bone marrow or stem cell transplant
Hydroxyurea
Avoid hypoxia - no high altitudes, pregnancy, anaesthesia, exercise

68
Q

What is some good supportive therapy for sickle cell disease

A

Folic acid
Good nutrition
Transfusion
Hydration
Prophylaxis

69
Q

HbC mutation

A

Position 6
Glu to lys

70
Q

Who is likely to have HbC

A

17-28% west Africans and some African Americans

71
Q

What makes HbC worse

A

Usually mild but infections make it worse

72
Q

Blood film in HbC

A

Normochromic normocytic anaemia
Maybe micro/hypo
Target cells
Reticulocytosis with some NBRC maybe
Mild chronic haemolysis

73
Q

Most common Hb co haemoglobinopathy

A

HbSC
Get HbS from one and HbC from the other
25% west African

74
Q

When do HbSC symptoms appear

A

Teenage years

75
Q

HbSC blood film

A

Target cells
Sickle cells
Crystals
Mild normochromic normocytic

76
Q

HbE mutation

A

26Glu to Lys

77
Q

Heterozygous HbE

A

Asymptomatic

78
Q

Homozygous HbEE resembles what

A

Resembles IDA or beta Thalassaemia

79
Q

HbEE blood film

A

Marked microcytic anaemia
MCV 50-70fL
Target cells

80
Q

What happens in HbE - splicing

A

Alternate splicing site in Beta Globin mRN
Instability between alpha/beta globin
Less beta chain synthesis

81
Q

HbE ethnicity

A

30% SE Asia

82
Q

What are some screening tests for haemoglobinopathies

A

Solubility or slide sickling tests
Deoxygenated blood with dithionate to induce crystal formation (increased solubility = positive test)

83
Q

Confirmatory tests for haemoglobinopathies

A

HPLC or Hb electrophoresis (alkaline and acid)

84
Q

Order of Alkaline EP

A
  • A2 SD F A +
85
Q

Acid EP order

A
  • F A/A2/D S O C +
86
Q

What is polycythemia

A

Increased affinity Hb
Rare

87
Q

Cyanosis

A

Decreased affinity for Hb
Rarer than polycythemia

88
Q

What are unstable Hb

A

Hb that precipitates in vivo
Some haemolysis but not serious
Increased oxygen affinity usually

89
Q

What is HbM - chemical

A

Fe 2+ oxidised to Fe3+
Fe3+ increases O affinity
Cyanosis and hypoxia if above 30%

90
Q

Curve for HbM

A

Curve shift left as less oxygen delivered

91
Q

Congenital cause of HbM

A

NADH-dependent methaemoglobin reductase definitely

92
Q

Acquired cause of HbM

A

Antimalarials
Local anaesthetic from dentist
Sulphonamides

93
Q

Clinical/lab finding Hb

A

Choc brown blood on filter paper = screening
Blue skin
100% oxygen does not help

94
Q

How is HbM confirmed

A

Spectrophotometric methods

95
Q

How is HbM treated

A

IV methylene blue
Exchange transfusion
Hyperbaric oxygen

96
Q

Persistence of HbF caused by

A

Mutations/deletions/cross overs affecting beta and gamma chains

97
Q

Does persisting HbF matter

A

No , only in lab tests like Fetal cell count

98
Q

What is carboxyhaemoglobin

A

CO binds to haem - slower than O but with x240 affinity so it is not dropped to tissues

99
Q

Affect of carboxyhaemoglobin

A

Smokers can reach 20% saturation
15-20% headaches, dizziness, nausea
Greater than 50% is coma, convulsions, death

MELS302 (6 decks)

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