HEMOGLOBINOPATHIES Flashcards
1
Q
- Alpha and Zeta Globin genes
A
– Chromosome 16:
2
Q
Beta, Gamma, Delta and Epsilon
Globin genes
A
– Chromosome 11
3
Q
- Referred as: Alpha-like genes
A
– Chromosome 16:
4
Q
Referred as: Beta-like genes
A
Chromosome 11
5
Q
– Synthesize the alpha-globin chains
A
- Alpha globin gene (HBA1 & HBA2)
6
Q
– Codes for Beta-globin chain
A
- Beta globin gene (HBB)
7
Q
– Codes for gamma- globin chain
A
- Gamma globin genes (HBG1 and HBG2)
8
Q
– Codes for delta-globin chain
A
- Delta globin gene(HBD)
9
Q
Hemoglobin
COMMON NAMES
– Morphology
*___________, _____________
– Location
* ____________, ___________
– Content
________________
A
- HbS (sickle cell); HbC (Crystallization)
Gun-Hill, Constant-Spring - HbM(Methemoglobin)
10
Q
Hemoglobin
* SCIENTIFIC DESIGNATION
Nature of abnormality
A
– Substitution, Deletion,Addition, Fusion,
Elongation
11
Q
____________ symptoms of the disease have been traced in one Ghanaian family
A
1670
12
Q
Sickle cell anemia was 1st reported by a Chicago cardiologist, Herrick, in a West Indiana Student with severe anemia
A
1910
13
Q
Emmel recorded that sickling occurred in non-anemic patients and in patients who
were severely anemic.
A
1917
14
Q
In 1927 _____________ described the pathologic basis of the disorder and its relationship
to the hemoglobin molecule.
A
Hahn and Gillespie
15
Q
Beet reported that malarial parasites were present less often in blood films from
patients with SCD that in individuals without SCD
A
1946
16
Q
Pauling showed that when Hb S is subjected to electrophoresis, it migrates differently
than does Hb A
A
1949
17
Q
more severe disease
A
- Homozygotes (Hb SS)
18
Q
Less severe disease
A
Heterozygotes Hb S (Hb SC or Hb S-Bthal)
19
Q
Asymptomatic but may have mild
symptoms
– Military boot camp and High level athletics
A
- Heterozygotes (Hb AS)
20
Q
Glutamic acid(GAG) is replaced by Valine(GTG)
A
- On the Beta chain at Position 6
21
Q
Thymine replaces adenine
A
Mutation occurs in nucleotide 17
22
Q
Quaternary structure of the molecule does
not produce a hydrophobic pocket for
valine
A
- Hb S – fully oxygenated
23
Q
– Creates a hydrophobic pocket (Phe 85 &
Leu 88)
Allows the valines from adjacent Hb S
molecules to BIND
A
- Deoxygenation
24
Q
Sickling Begins – oxygen saturation decreases
to less than 85%
A
- Homozygotes
25
Sickling Begins – Oxygen saturation is reduced
to less than 40%
* Heterozygotes
26
Reduction in pH
– Increase in 2,3 BPG
* Decrease in oxygen tension
27
* END RESULT: Occlusions of __________ and _________ and infarction of surrounding
tissue.
capillaries and arterioles
28
* 2 FORMS OF SICKLE CELL:
1. Reversible Sickle Cell
2. Irreversible Sickle Cell
29
* Change shape in response to oxygen tension
* Circulate as normal biconcave discs when fully
oxygenated but undergo hemoglobin
polymerization
1. Reversible Sickle Cell
30
* Seen in PBS – elongated sickle cells with a
point at each end
* Recognized as ABNORMAL by the spleen
2. Irreversible Sickle Cell
31
* Other Reason Affects the Sickling process:
Microparticles, previously known as ________
“cellular dust”
32
* More than _________ hemoglobin variants are known;
1200 hemoglobin
33
8 genotypes causes SEVERE DISEASES
– Hb SS,
Hb S-B0-thal,
severe Hb S-B1-thal,
Hb SD-Punjab,
Hb SO-Arab,
Hb SC-Harlem,
Hb CS-Antilles, and
Hb S-Quebec-CHORI.
34
3 genotypes cause MODERATE DISEASES
Hb SC, moderate
Hb S-B1-thal,
and Hb AS-Oman
35
3 genotypes cause MILD DISEASE
– mild Hb S-B silent-thal,
Hb SE, and
Hb SA-Jamaica Plain
36
* 2 produce very mild disease:
– Hb S-HPFH
and Hb S with
a variety of mild variants.
37
1. VASOOCCLUSIVE CRISIS
* Frequency of painful episodes varies from
none to ___________
– Average: episodes persists for _______ or may
last for weeks
six years
4-5 years
38
2nd most common cause of hospitalization
3. Acute Chest Syndrome (ACS)
39
– 3rd most common cause of death among adults with SCD
– Most common inciting factors: Pulmonary infection, fat embolism, pulmonary infarction à decrease oxygen
3. Acute Chest Syndrome (ACS)
40
_________ is administered to maintain saturation at greater than or equal to95% and intravenous fluids to
prevent dehydration
Oxygen
41
FES secondary to BMN is a rare but often fatal sequalae of SCD.
– It occurs more often in often in Hb SC (43%) and at similar frequency in Hb S-b1-thal (17%) and Hb SS
(19%)
4. Fat Embolism syndrome(FES) and Bone marrow necrosis(BMN)
42
Is a serious and potentially fatal sequela of SCD
– An association has been documented between the development of PHT and the nitrous oxide (NO)
pathway,
– Patients with SCD have decrease in NO, and leads to vasoconstriction and hypertension.
5. Pulmonary Hypertension (PHT)
43
– Pose a major problem for SCD patients
Increased susceptibility to life threatening infections from _________, ________, __________
– Common cause of death, especially in the first __________
– __________ are exacerbated by the autosplenectomy effect
* Gradually loses its ability to function
* Not effectively clear organism from the blood
Staphylococcus aureus, Streptococcus
pneumoniae, and Haemophilus influenzae.
3 years of life
Septicemia
44
Shortened RBC survival (between 16-20 days)
7. Chronic Hemolysis
45
Continuous screening and removal of sickle cells by the spleen perpetuate the chronic hemolytic
anemia and autosplenectomy effect
* RBC hemolysis releases free hemoglobin, which disrupts the argnine-NO pathway, resulting in the
sequestration and lowering of NO à Pulmonary hypertension
– Another major sequelae of hemolysis is renal hyper-filtration and dysfunction
* which can be detected early by an increased glomerular filtration rate
7. Chronic Hemolysis
46
Result from the sudden arrest of erythropoiesis caused by folate depletion
– Folic acid deficiency as a cause of exaggerated anemia in SCD
– Prescribe prophylactic folic acid for patients with SCD
8. Megaloblastic Episodes
47
Most common life-threatening hematologic complications and usually associated with infection
(Parvovirus)
– Are short lived , Require no therapy
– Sickle cell patients usually can compensate for the decrease in RBC survival by increasing bone
marrow output
9. Aplastic Episode(Bone marrow failure)
48
In patients with severe anemia, cardiomegaly can develop as the heart works harder to maintain adequate blood flow and
tissue oxygenation
10. Cardiac Abnormalities
49
Impaired blood supply to the head of the femur and humerus results in a condition called avascular necrosis (AVN)
– 50% of patients with SCD developed AVN by age 35 years
11. Bone and skin abnormalities
50
occurs in approximately 11% of children with SCD before age 20 years.
Hemorrhagic or ischemic stroke
51
Due to retinal ischemia and neovascularization
– Begins at 10 years of age
– Retinopathy occurs at a rate of 45% in patients with
Hb SC, 11% with
Hb SS, and 17%
with Hb S-B-thal by early adulthood
Retinopathy
52
Incidence with Malaria
Greatest frequency in_________, _______, _______, _________
Central Africa, the
Near East, the Mediterranean region, and
parts of India.
53
____________ - offer some protection
against cerebral falciparum malaria in
young patients
Sickle gene
54
__________ used oxygen in the cell
– Causes the cells to sickle
Malaria
55
Laboratory Diagnosis
* Observed on a wright-stained PBS
Normocytic, Normochromic
– Long, curved cell with a pointed at each
end (sickle cell) – HALLMARK OF SCD
– Moderate to marked polychromasia
* 10% & 25% reticulocyte count
– Increased RDW
– Moderate leukocytosis with neutrophilia
and a mild shift to ward immature
granulocytes
Sickle cell disease malaria
56
________________
______ – not elevated
* ____________ – Present
_____________– Elevated in all forms
of SCD
*______________ – normal in young patients
but tend to be elevated later in life
* __________________
– Elevated levels of indirect and total bilirubin
with accompanying jaundice
LAP
Thrombocytosis
Immunoglobulin A
Serum ferritin
Chronic hemolysis
57
* DIAGNOSIS is a 2-STEP POCESS
– 1. demonstrate the insolubility of
deoxygenated Hb S in solution
– 2. confirmation of its presence using:
* hemoglobin electrophoresis
* high-performance liquid chromatography
(HPLC)
* Capillary electrophoresis
58
* Older screening test:
– Detects Hb S insolubility by inducing sickle
cell formation on a glass slide
* On a slide: drop of blood + a drop of 2% Na
metabisulfite
* Sealed under a coverslip
* Hgb in RBCs is reduced to deoxygenated
form à polymerization à sickling of cell
(microscopically)
* Slow and hassle to perform
59
Laboratory Diagnosis: Hemoglobin Solubility test
* Most commons screening test
* Capitalizes on the decreased solubility of
deoxygenated Hb S in solution, producing
TURBIDITY
* BLOOD + Buffered salt Solution containing reducing
agent (sodium hydrosulfite (dithionite)) + a
detergent-based lysing agent (Saponin)
* Saponin: dissolves membrane lipids à release HGB
* Dithionite: reduces ferrous to ferric (does not bind
oxygen) à deoxygenated Hb S polymerizes
* TURBID -Deoxygenated Hb S
* CLEAR– Non sickling hemoglobins
60
*Laboratory Diagnosis: Hemoglobin Solubility test
False-Positive
– _______________
- _______________
- ________________
* False-Negative
- ______________
- ______________
- Hyperlipidemia
– Few rare hemoglobinopathies
– Too much blood added
– Infants younger than 6 months
– Low hematocrit
61
– common 1st step in confirmation of hemoglobinopathies
* Alkaline Hemoglobin electrophoresis
62
some hemoglobin assume a positive charge migrate toward the cathode (negative pole)
Acid pH
63
– Separates hgb types in a cation exchnage
column and usually requires only one
sample injection
HPLC
64
Can identify and quantify low levels of Hb
A2 and Hb F, but comigration of Hb A2 and
Hb E occurs
* HPLC
65
– It is BEST use for thalassemias
* HPLC
66
CONFIRMATORY TECHNIQUE that is expensive and complex
Requires well trained and experienced laboratory personnel
* Uses electric current to push the hgb molecules across a pH gradient
– They migrate through the pH gradient until the hgb reaches its isoelectric point (net
charge of zero)
– The migration stops and the hgb molecules accumulate at their isoelectric position
– Isoelectric point differences of as little as 0.02 pH units can be effectively separated
* Isoelectric Focusing (IEF)
67
Requires a more sophisticated approach
* Neonatal Screening
68
* Using 3 techniques: _____________, ____________, _____________
adapted IEF,
HPLC
& Reversed-phase HPLC
69
* Some reference laboratories may use:
mass spectroscopy, matrix-assisted laser desorption- ionization time-of-flight (MALDI-TOF) mass
spectrometry, or IEF to separate hemoglobin types, or nucleic acid identification of the genetic
mutation.
70
* Common indicators of inflammation
___________ – good predictor of sickle cell complications and mortality
– __________ level exhibit variability too great to reliably predict episodes
–___________ both elevated during VOC and acute chest syndrome
– ____________ – indicators in clinical practice
– ____________ – elevated before and during VOC
– Elevated Malondialdehyde (MDA) & depleted alpha-tocopherol–in lipid damage from oxidative
stress
– _____________rises during bouts of inflammation
– THE MOST PROMISING : _________________
WBC Count
ESR & CRP
CRP & sPLA2
IL6,IL10 and protein S
Annexin A5
Alpha tocopherol & CRP
IL6,IL10, Vascular cell adhesion molecule 1 (VCAM-1) and sPLA2
71
* Benign condition
* Generally asymptomatic
* No significant clinical or hematologic manifestations
* Under extremely hypoxic conditions
– Systemic sickling and vascular occlusion with pooling of
sickled cells in the spleen, focal necrosis in the brain,
rhabdomyolysis, and even death can occur
* Patient may develop splenic infarcts and cause sickling
– Severe respiratory infection, unpressurized flight at high
altitudes and anesthesia
* Failure to concentrate urine – CONSISTENT abnormality
in SCT
* Strenuous exercise and Military Recruits
Heterozygous state (Hb AS)
72
Electrophoresis or HPLC - presence
of __________ and _____________
Hb S and Hb A
73
* Most common non sickling variant encountered
in the US
Hemoglobin C
74
* 3RD most common in the world
Hemoglobin C
75
____________________________
– Crystalizes in the oxygenated state
__________________________
– Less splenic sequestration and hemolysis
Hb C is less soluble than Hb A
* Shorter Hb C crystal does not alter RBC
76
* Form a short, thick crystal within the RBC
Hemoglobin C
77
CLINICAL FEATURES
– Milder disease compared to SCD
– Mild splenomegaly and hemolysis
– No Vasoocclusive crises
– Heterozygous hemoglobin C trait
(Hb AC)
* Asymptomatic
Homozygous Hemoglobin C
78
* Seen in PBS
* Seen on wet preparation
HGB is concentrated within boundary of
the crystal
* Densely stained and vary in size
* Appear oblong with pyramid-shaped or
pointed ends
Hexagonal Crystals within RBCs
79
Hemoglobin solubility – NEGATIVE
– DEFINITIVE DIAGNOSIS- using
electrophoresis, HPLC, or nucleic acid testing
– No Hb A is present in Hb CC
– Hb C is present > 90%
* Hg F < 7%
* HbA2 – 2%
– Hb AC trait
* Hb A – 60%
* Hb C – 30%
Hemoglobin C
80
* Double substitution on the B chain
– Identical Hb S substitution
* Valine for glutamic aside at position6 of the B chain
– Same as the Hb Korle Bu Mutation
* Substitution at position 73 of aspartic acid for asparagine
– Abnormal hgb migrates with Hb C on alkaline hgb electrophoresis.
* Heterozygous – asymptomatic
* Heterzygosity for Hb S and Hb C- Harlem – similar crises with Hb SS disease
Hemoglobin C- Harlem (Hemoglobin CGeorgetown)
81
Hemoglobin C- Harlem (Hemoglobin CGeorgetown)
Solubility test – ____________
* Confirmatory test – ______________
POSITIVE
hemoglobin
electrophoresis or HPLC
82
First Describe in 1954
Hemoglobin E
83
a Beta chain variant in which lysine is substituted for glutamic acid in
position 26
Hemoglobin E
84
is both a qualitative defect (because of the amino acid
substitution in the globin chain) and quantitative defect with Beta thalassemia
phenotype (because of decreased production of the mutated globin chain)
Hb E mutation
85
_____________is asymptomatoc
Hb E trait
86
_____________ results in more severe, resembles the severity B-thalasemia, requiring regular blood
transfusions
Hb E-B0-Thal
87
– Hb M migrates slightly more slowly than _________
– The electrophoresis should be performed on agar gel at pH _______
for clear separation.
Hb A
7.1
88
