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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
Bone marrow changes in HbH disease
Erythroid hyperplasia Splenomegaly
26
Is Hbh affected by a haemolytic crisis
Yes Infection, oxidative drugs, pregnancy
27
What is Hb Bart disease
4 gene alpha deletion No alpha chains made so no HbF/Gower2/HbA
28
What are Hb Bart
An unstable tetramer made from excess gamma chains High affinity for oxygen so doesn’t deliver
29
Outcome of Hb Bart
Did in utero or hours after birth Mother at increased risk of toxemia and post partum haemorrhage
30
How is Hb Bart detected
DNA analysis of chorionic villus, amniotic fluid, cord blood
31
Hb Bart blood film
Severe microcytosis hypochromic anaemia Basophilic stippling Dysplastic NRBCs
32
What is seen in hydrops fetalis syndrome
Anaemia Extramedullary haemopoiesis Organ failure Total body odema
33
How do Hb H appear on film
Golf ball inclusion bodies Retic stain
34
How do HbH affect RBC
They are easily oxidised and they precipitate and denature distorting RBC so they get stuck in the spleen and so survival decrease
35
How to diagnose Thalassaemia
Clinical examination Family history - ethnicity Blood film Hb electrophoresis- acid and alkaline PCR to find specific mutation
36
FBC for Thalassaemia
Increased RBC count Low MCV Low RDW Reticulocytosis
37
If a co existing Haemoglobinopathy is suspected what test do you do
HPLC or Hb electrophoresis
38
What happens in beta/alpha Thalassaemia in electrophoresis
Beta - low or absent HbA, increase HbF/A2 varies Alpha - Hbh present maybe Bart, low Hb A/A2/F
39
What are haemoglobinopathies
Gene defect causing a structural defect in one of the Globin genes
40
What is the slient carrier state beta
Small decrease in production of one Beta gene Asymptomatic nothing on blood film
41
What is beta Thalassaemia minor
Partial decrease in one or full in one beta gene
42
Beta Thalassaemia minor blood Film
Mild microcytic hypochromic anaemia Asymptomatic Target cells Basophilic stippling Poikilocytosis Elliptocytes
43
How do the other Hb act in beta Thalassaemia minor
Decreased HbA, increases HbF and maybe A2
44
Why can NRBCs be problematic for FBCs in analysers
NRBC resist lysis and can be counted as a lymphocyte Showing a false WBC increase
45
Beta Thalassaemia intermedia blood film
Lots of NRBC target cells, more severe anaemia than B Thalassaemia minor Basophilic stippling Teardrops Elliptocytes Poikilocytes
46
Does beta Thalassaemia need blood transfusions
No even though it’s more severe Count get splenectomy
47
When does a total WBC corrected count need to be done
When more than 5 NRBC per 100 WBC
48
When does beta Thalassaemia major present
When the switch to HbA fail at 3-6 months
49
Beta Thalassaemia major blood film
Marked microcytic hypochromic anaemia TARGET CELLS tear drops Elliptocytes Fragments Poikilocytosis, anisocytosis Erythroblasts Basophilic stippling Alpha inclusion bodies
50
What happens overall to RBC in Beta Thalassaemia major
Haemolysis Ineffective erythropoiesis HbA can be absent
51
Genotype of beta Thalassaemia major
Both genes half missing Both genes missing 1 full gene missing, and other half gene missing
52
Clinical features of beta Thalassaemia major
Hepatosplenomegaly Extramedullary erythropoiesis causes marrow expansion = skeletal changes and growth retardation Infections Iron overload
53
Beta Thalassaemia major treatment and cure
Treatment - blood transfusions, splenectomy (wait until 7-8years), iron chelation therapy Cure - bone marrow transplant, gene therapy
54
Heterozygous sickle cell blood film
Mild No anaemia
55
Heterozygous sickle cell found where
20-40% frequency in Africa Protection against malaria
56
What leads to a heterozygous sickle cell crisis
Sickle cells will precipitate at low oxygen pressure From severe fever, hypoxia, high altitude, plane, lung infections
57
What does the amino acid substitution cause in the sickle cells
Position 6 Glu to Val Means the tertiary structure now has a hydrophobic group exposed leading them to clump together and get distorted
58
Order of what deoxygenation does to sickle cells (allosteric change) - how are sickle cells formed
Polymer forms Ca influx and water and K leaves Cell is dehydrated Precipitation of polymers to form sickle cells
59
What happens in the body with sickle cells
Increase in blood viscosity Decrease flow Increase hypoxia and lower pH promotes more sickling Haemolysis and occlusion Anaemia Infarction and inflammation
60
Sickle cell crisis leads too
Aplasia (after infection parvovirus) Acute chest syndrome Visceral sequestration Vasooclusion causing infarctions in eyes, lungs, bones etc
61
Where does visceral sequestration happen in a sickle cell crisis
Spleen, liver, lungs in infants and children
62
What is acute chest syndrome - sickle cell crisis
Vasooclusive crises of pulmonary vascular Associated with fever/chest pain/pulmonary infiltrates
63
What triggers vasooclusion which causes infarcts during a sickle cell crisis
Hypoxia, acidosis (low pH encourages sickling), dehydration, fever, cold temp
64
Where do sickle cell infarctions happen
Bones Lungs Liver Penis Eyes CNS UT Spleen
65
Sickle cell blood film
Chronic haemolytic anaemia Normocytic normochromic anaemia Polychromatic, poikilocytosis, anisocytosis Target cells Sickle cells Reticulocytosis unless aplastic
66
If spleen is infarcts in sickle cell what does the blood film look like
Marked poikilocytosis NRBC Basophilic stippling Spherocytosis Pappenheimer bodies Howell jolly bodies
67
Treatment for sickle cell
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
What is some good supportive therapy for sickle cell disease
Folic acid Good nutrition Transfusion Hydration Prophylaxis
69
HbC mutation
Position 6 Glu to lys
70
Who is likely to have HbC
17-28% west Africans and some African Americans
71
What makes HbC worse
Usually mild but infections make it worse
72
Blood film in HbC
Normochromic normocytic anaemia Maybe micro/hypo Target cells Reticulocytosis with some NBRC maybe Mild chronic haemolysis
73
Most common Hb co haemoglobinopathy
HbSC Get HbS from one and HbC from the other 25% west African
74
When do HbSC symptoms appear
Teenage years
75
HbSC blood film
Target cells Sickle cells Crystals Mild normochromic normocytic
76
HbE mutation
26Glu to Lys
77
Heterozygous HbE
Asymptomatic
78
Homozygous HbEE resembles what
Resembles IDA or beta Thalassaemia
79
HbEE blood film
Marked microcytic anaemia MCV 50-70fL Target cells
80
What happens in HbE - splicing
Alternate splicing site in Beta Globin mRN Instability between alpha/beta globin Less beta chain synthesis
81
HbE ethnicity
30% SE Asia
82
What are some screening tests for haemoglobinopathies
Solubility or slide sickling tests Deoxygenated blood with dithionate to induce crystal formation (increased solubility = positive test)
83
Confirmatory tests for haemoglobinopathies
HPLC or Hb electrophoresis (alkaline and acid)
84
Order of Alkaline EP
- A2 SD F A +
85
Acid EP order
- F A/A2/D S O C +
86
What is polycythemia
Increased affinity Hb Rare
87
Cyanosis
Decreased affinity for Hb Rarer than polycythemia
88
What are unstable Hb
Hb that precipitates in vivo Some haemolysis but not serious Increased oxygen affinity usually
89
What is HbM - chemical
Fe 2+ oxidised to Fe3+ Fe3+ increases O affinity Cyanosis and hypoxia if above 30%
90
Curve for HbM
Curve shift left as less oxygen delivered
91
Congenital cause of HbM
NADH-dependent methaemoglobin reductase definitely
92
Acquired cause of HbM
Antimalarials Local anaesthetic from dentist Sulphonamides
93
Clinical/lab finding Hb
Choc brown blood on filter paper = screening Blue skin 100% oxygen does not help
94
How is HbM confirmed
Spectrophotometric methods
95
How is HbM treated
IV methylene blue Exchange transfusion Hyperbaric oxygen
96
Persistence of HbF caused by
Mutations/deletions/cross overs affecting beta and gamma chains
97
Does persisting HbF matter
No , only in lab tests like Fetal cell count
98
What is carboxyhaemoglobin
CO binds to haem - slower than O but with x240 affinity so it is not dropped to tissues
99
Affect of carboxyhaemoglobin
Smokers can reach 20% saturation 15-20% headaches, dizziness, nausea Greater than 50% is coma, convulsions, death

MELS302 (6 decks)

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