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Hematology > Hematology Exam 6 (All about hemoglobin) > Flashcards

Hematology Exam 6 (All about hemoglobin) Flashcards

1
Q

What is the basic structure of hemoglobin?

A

Tetramer composed of 4 polypeptide (Globin) chains and 4 heme groups

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2
Q

What is the basic structure of heme?

A

Protoporphyrin ring bound to ferrous (Fe2+) iron

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3
Q

How many oxygen molecules can each iron atom on heme bind?

A

1

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4
Q

List the heme precursors in order from succinyl-CoA and glycine to heme (ferroprotoporphyrin IX) AND where they are formed (mitochondria or cytosol?)

A
  1. Succinyl CoA + Glycine (mitochondria)
  2. Aminolevulinic acid (mitochondria)
  3. Porphobilinogen (cytosol)
  4. Hydroxymethylbilane (cytosol)
  5. Uroporphyrinogen III (cytosol)
  6. Coproporphyrinogen (cytosol)
  7. Protoporphyrinogen IX (mitochondria)
  8. Protoporphyrin IX (mitochondria)
  9. Heme (mitochondria)
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5
Q

What globin genes are present on chromosome 16? 11? How many of each?

A

Alpha chain –> 4 genes total, 2 on each chromosome 16 (genotype is aa/aa)
Beta chain –> 2 genes total, 1 on each chromosome 11 (genotype is B/B)

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6
Q

What type of iron does transferrin carry? what type of iron is it reduced to?

A

Transferrin carries FERRIC (Fe3+) iron
Reduced to FERROUS (Fe2+) iron to form heme

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7
Q

How many molecules of oxygen can hemoglobin carry?

A

4 molecules of oxygen – 1 per globin chain

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8
Q

Where does heme synthesis take place?

A

Mitochondria and cytoplasm of RBC precursors (Does not occur in adult RBC)

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9
Q

What is the globin chain composition of HGB A? What is the percentage found in adults?

A

2 alpha, 2 beta (95% in normal adults)

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10
Q

What is the globin chain composition of HGB F? What is the percentage found in adults?

A

2 alpha, 2 gamma (<3.5% in adults)

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11
Q

What is the globin chain composition of HGB A2? What is the percentage found in adults?

A

2 alpha, 2 delta (1-2% in adults)

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12
Q

What is the major hemoglobin at birth? What is the major hemoglobin after 6 months?

A

HGB F at birth; HGB A after 6 months

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13
Q

List the names of the 3 embryonic hemoglobins

A

Gower 1, Gower 2, Portland

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14
Q

What is the regulation of production of heme?

A

Negative feedback, so more heme = less ALA synthase produced and hypoxia = more EPO = increased RBC production

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15
Q

What is the shape of the hemoglobin oxygen dissociation curve?

A

Sigmoidal curve (S-shape)

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16
Q

What is a shift to the left on the hemoglobin oxygen dissociation curve?

A

Increased affinity for O2 because O2 levels are low in the body.

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17
Q

What is a shift to the right on the hemoglobin oxygen dissociation curve?

A

Decreased affinity for O2 because O2 levels are high/sufficient.

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18
Q

Compare the pO2 in lungs vs tissues

A

Lungs: high pO2, high O2 saturation
Tissues: low pO2, low O2 saturation

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19
Q

What is 2,3-BPG and what is its affect on hemoglobin/oxygen?

A

2,3-BPG controls hemoglobin affinity for oxygen.
Deoxyhemoglobin (tense form) = stabilized by 2,3-BPG when oxygen levels are low (INC BPG, LOW O2)

Oxyhemoglobin (relaxed form) = no 2,3-BPG bound because oxygen affinity is high and favors binding of oxygen (DECR BPG, HIGH O2)

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20
Q

When is 2,3 BPG high?

A

When oxygen levels are low (low oxygen affinity) - tensed state

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21
Q

When is 2,3 BPG low?

A

When oxygen levels are high (high oxygen affinity) - relaxed state

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22
Q

Oxygen affinity vs oxygen delivery

A

Oxygen affinity = favors binding of oxygen
Oxygen delivery = does not favor binding of oxygen, wants to deliver it to tissues

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23
Q

What are some causes of shifts to the left (HIGH OXYGEN AFFINITY)

A

DECREASED 2,3 BPG
DECREASED body temp
INCREASED pH (alkalosis)
Presence of HGB variants with high affinity for O2

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24
Q

What are some causes of shifts to the right (LOW OXYGEN AFFINITY) – Shift to the right, wont hold tight

A

INCREASED 2,3 BPG
INCREASED Body temp
DECREASED pH (acidosis)
Presence of HGB variants with low affinity for O2

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25
Q

Is oxygen affinity/pO2 higher in the lungs or the tissues?

A

LUNGS, tissues have low pO2 with low affinity

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26
Q

Shift to the left = _________ affinity and _______ delivery

A

Increased affinity, decreased delivery

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27
Q

Shift to the right = _______ affinity and ______ delivery

A

Decreased affinity, increased delivery

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28
Q

BRIEFLY list the order in which CO2 travels in tissues

A

CO2 enters RBC –> becomes H2CO3 (carbonic acid) –> becomes HCO3- (bicarbonate) after releasing H+ –> that H+ binds oxyHGB –> oxygen released into tissues

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29
Q

BRIEFLY list the order in which CO2 travels in lungs

A

O2 diffuses in cells –> binds deoxyHGB –> H+ released and binds HCO3- (bicarbonate) –> becomes H2CO3 (carbonic acid) –> becomes H2O and CO2 –> CO2 diffuses out of cell and exhaled by lungs

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30
Q

Define dyshemoglobins

A

Hemoglobins that are unable to properly transport oxygen

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31
Q

What are the 3 dyshemoglobins?

A

Methemoglobin, sulfhemoglobin, and carboxyhemoglobin

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32
Q

Describe methemoglobin

A

Heme bound to FERRIC iron so it cannot bind oxygen. High levels turn blood a BROWN color and can turn skin blue –> treat with IV methylene blue to reduce ferric iron to ferrous iron

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33
Q

Describe sulfhemoglobin

A

Hemoglobin bound to sulfur instead of iron –> turns blood a GREEN color and can form after use of certain drugs or sulfur chemicals

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34
Q

Describe carboxyhemoglobin

A

Heme bound to carbon monoxide –> binds 240X tighter than oxygen –> huge shift to the left turns blood CHERRY RED color. Treat with oxygen (seen with people in house fires)

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35
Q

Define hemoglobinopathy and thalassemia. How are they different?

A

Hemoglobinopathy: qualitative hemoglobin defect –> making abnormal globin chains

Thalassemia: quantitative hemoglobin defect –> not making enough globin chains

36
Q

Differentiate heterozygous and homozygous hemoglobinopathies

A

Het = one affected gene (trait)
Homo = two affected genes (disease) more severe

37
Q

What is the structural formula of the abnormal HGB in sickle cell anemia vs sickle cell trait?

A

They are both alpha2beta2 ^ 6Glu-Val
SCD = HGB SS
SCT = HGB SA

38
Q

What is the zygosity of HGB SS vs HGB SA?

A

HGB SS = homozygous = more severe
HGB SA = heterozygous

39
Q

What is the sickle solubility test results for HGB SS vs HGB SA?

A

They would both be positive since HGB S is present.

40
Q

What does SCD refer to?

A

sickle cell disease - diseases that involve the production of HGB S

41
Q

What information does the sickle solubility/dithionite solubility/sickle sol test provide?

A

Screening test to see if HGB S is present (if turbidity is present, then positive)

42
Q

Clinical manifestations of SCD

A

vaso-occlusive crisis, acute chest syndrome, splenic sequestration, causing episodes of recurring pain

Sickle cell trait will only show symptoms in extremely hypoxic conditions

43
Q

Peripheral smear findings of HGB SS vs HGB SA

A

HGB SS: sickle cells (drepanocytes), target cells, nRBCS, spherocytes, basophillic stippling, HJ bodies, Pappenheimer bodies, leukocytosis, polychromasia

HGB SA: target cells

44
Q

Why is Sickle sol not performed on infants less than 6 months old?

A

Because there is high HGB F levels which can lead to false negatives/HGB S not developed yet

45
Q

What information does the HGB electrophoresis provide?

A

Tells us how much HGB S is present

46
Q

HGB electrophoresis results for HGB SS vs HGB SA

A

HGB SS = >80% HGB S, no HGB A, higher HGB F
HGB SA = >60% HGB A, <40% HGB S, normal other HGBs

47
Q

Treatment for HGB SS?

A

Supportive care, bone marrow/stem cell transplants

48
Q

What is the structural formula of HGB C?

A

alpha2beta2 ^ 6 Glu-Lys

49
Q

HGB C disease vs trait

A

HGB CC = disease
HGB AC = trait, asymptomatic

50
Q

What is the most common non-sickling HGB variant in the US?

A

HGB C

51
Q

HGB C peripheral smear

A

Washington monument crystals, target cells, reticulocytes, nRBCs

52
Q

HGB C sickle sol results

A

negative

53
Q

HGB C disease vs HGB C trait Electrophoresis results

A

HGB C disease: no HGB A, >90% HGB C
HGB C trait: 70% HGB A, 30% HGB C

54
Q

Why is there no HGB A present in a patient with HGB C disease?

A

There are no normal beta chains to make HGBA

55
Q

Structural formula of HGB E

A

a2b2 ^ 26Glu-Lys

56
Q

Population most commonly affected by HGB E

A

SE Asia, most common in Cambodia/Laos/Thailand

57
Q

Sickle sol results with HGB E

A

Negative

58
Q

HGB E disease vs HGB E results

A

HGB EE = >90% HGB E very low MCV
HGB AE = asymptomatic, 25-30% HGB E

59
Q

What are the genetics behind HGB SC?

A

One HGB S gene and one HGB C gene = NO normal beta chains made

60
Q

Clinical findings of HGB SC?

A

No significant symptoms until teenage years, can have vaso-occlusive complications but not as common as sickle cell anemia

61
Q

Peripheral smear findings of HGB SC?

A

Few sickle cells, target cells, HGB SC crytals that look like “hands in gloves”

62
Q

Sickle sol results for HGB SC?

A

Positive

63
Q

Electrophoresis results for HGB SC?

A

45% HGB S, 45% HGB C, normal HGBF, no HGB A

64
Q

What is alpha+

A

deletetion of one a-globin gene leading to decreased production of a-chains

65
Q

What is alpha0

A

deletion of both a-globin genes, leading to absent production of a-chains

66
Q

What is beta+

A

mutations of B-globin gene leading to partial deficiency of b-chains

67
Q

What is beta0

A

mutations of b-globin gene in which no b-chains are produced

68
Q

How does an imbalanced globin chain ratio and reduced/absent production of a globin chain lead to clinical manifestations in thalassemias?

A

It leads to decreased HGB synthesis, decreased survival of RBCs, leading to microcytic/hypochromic RBCs and ineffective erythropoiesis

69
Q

Which globin chains increase to compensate for a decrease in b-chains in b-thalassemia?

A

delta chains and gamma chains leading to excess HGBA2 and HGBF

70
Q

Why are patients with b-thalassemias often asymptomatic until ~6 months?

A

You only make HGBF until ~6 months and there are no beta chains on HGB F, only alpha and gamma.

71
Q

What causes bone deformities in patients with untreated, severe forms of b-thalassemia?

A

The anemia stimulations EPO production leading to erythroid hyperplasia in BM

72
Q

What are two abnormal HGBs that develop in patients with A-thalassemia? Why do they develop in these patients and not in patients with B-thalassemia? What is the globin chain composition of each?

A

HGB H (4 beta chains) and HGB Bart (4 gamma chains). These do not develop in patients with B-thalassemia because beta chains are not present at birth (not in HGB F).

73
Q

What is the mechanism/why is anemia caused by a B-thalassemia?

A

Excess alpha chains precipitate leading to damage to RBC membrane causing premature death of RBC precursors in BM –> ineffective erythropoiesis

74
Q

Describe HGB Lepore thalassemia

A

Fusion of delta-beta globin genes
homozygotes: no normal delta or beta chains made so no HGB A, mostly HGB F
heterozygotes: decreased HGB A with increased HGB F

75
Q

What is silent carrier b-thalassemia? (including genetics, clinical presentations, and lab results)

A

Normal a/b chain ratios
No clinical presentations
Small decrease in beta chain production

76
Q

What is b-thalassemia minor? (including genetics, clinical presentations, and lab results)

A

B-thalassemia trait
One affected globin gene, one normal gene
Mild, asymptomatic anemia
Microcytic/hypochromic with target cells, elliptocytes, basophilic stipping

77
Q

What is b-thalassemia major? (including genetics, clinical presentations, and lab results)

A

AKA Cooley’s Anemia
HGB A absent or severely decreased depending on B+ or B0
Severe anemia
Microcytic/hypochromic with target cells, dacrocytes, elliptocytes, HJ bodies, pappenheimer bodies, low retic count, erythroid hyperplasia in the bone marrow

78
Q

What is HPFH?

A

Hereditary persistence of fetal hemoglobin
Increased HGB F production as an adult; assessed using Kleihauer Betke

79
Q

What is HGB Lepore?

A

Fusion of delta-beta globin genes
homozygote: no HGB A
heterozygote: decreased HGB A

80
Q

What Is silent carrier a-thalassemia? (including genetics, clinical presentations, and lab results)

A

1 a gene deleted, 3 functional a genes (-a/aa)
No abnormalities
SLIGHT decrease in alpha chains

81
Q

What is a-thalassemia minor? (including genetics, clinical presentations, and lab results)

A

2 deleted genes, 2 functional genes
Homo form = (-a/-a)
Het form = (–/aa)
Asymptomatic

82
Q

What is HGB H disease? (including genetics, clinical presentations, and lab results)

A

3 genes deleted, 1 functional (–/-a)
Characterized by tetramer of B chains (B4)
10-40% HGB Bart at birth, then switch to HGB H
Causes denaturation of hemoglobin and decreased RBC survival

83
Q

What is HGB Bart Hydrops Fetalis Syndrome?(including genetics, clinical presentations, and lab results)

A

All 4 a genes deleted, NO functioning genes
(–/–)
Tetramer of gamma chains
Incompatible with life, baby will die due to cardiac failure/no oxygen delivery to tissues

84
Q

*Which poikilocyte can be seen in large amounts in patients with thalassemias

A

Target cells (Codocytes)

85
Q

What thalassemia is associated with ineffective erythropoiesis?

A

B-thalassemia

86
Q

Supravital staining may allow for visualization of inclusion bodies in which type of thalassemia? What are the inclusions made of? What is the terminology used to describe these cells?

A

Can detect HGB H alpha thalassemia with the use of Brilliant cresyl blue or new methylene blue. They look like greenish-blue bodies with a “golf ball” appearance.

87
Q

How can a patient have a hemoglobinopathy AND thalassemia?

A

If they inherited thalassemia gene from one parent, HGB S gene from the other, for example.

Hematology (10 decks)

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