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Heme Onc Royal College > Hemoglobinopathies > Flashcards

Hemoglobinopathies Flashcards

1
Q

what variables can shift the oxygen saturation curve?

A

pH, CO2, 2,3-BPG, temperature

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2
Q

what does a left-shifted oxygen sat curve mean?

A

you need a lower partial pressure of oxygen to have hemoglobin 50% saturated - which means hemoglobin holds on to oxygen, less likely to deliver oxygen to tissues

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3
Q

what does a right-shifted oxygen saturation curve mean?

A

a higher partial pressure of oxygen is needed to saturate hemoglobin - hemoglobin has less affinity for oxygen and more likely to deliver o2 to tissues

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4
Q

Composition of HbA

A

two alpha

two beta

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5
Q

Composition of HbF

A

two alpha

two gamma

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6
Q

Composition of HbA2

A

two alpha

two delta

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7
Q

Composition of Hb Gower I

A

two zeta

two epsilon

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8
Q

Composition of Hb Portland

A

two zeta

two gamma

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9
Q

Composition of Hb Gower II

A

two alpha

two epsilon

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10
Q

Composition of Hb Barts

A

four gamma chains

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11
Q

Composition of Hb H

A

four beta chains

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12
Q

what are the embryonic hemoglobin chains?

A

zeta

epsilon

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13
Q

when might you see an elevated hemoglobin F?

A
  • bone marrow failure syndromes
  • sickle-cell
  • beta-thal
  • hereditary persistence of hemoglobin F
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14
Q

when do you see hemoglobin barts?

A

four alpha gene deletion, resulting in tetramers of gamma chains

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15
Q

when do you see hemoglobin H disease?

A

three alpha chain deletion, resulting in tetramers of beta chains

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16
Q

how does a three alpha gene deletion manifest?

A 
hemoglobin A, hemoglobin H disease
mild anemia (usually NOT transfusion dependent), neonatal jaundice
can have marked clinical variability
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17
Q

what is hemoglobin E?

A

beta + mutation with decreased production of beta globin chains. if compound heterozygote with beta 0, can result in transfusion dependent phenotype

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18
Q

how can homozygous mutations of beta globin gene present?

A

as transfusion dependent or non transfusion dependent - variable!

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19
Q

genetics of non-transfusion dependent beta thal?

A

can be heterozygote for beta+ or beta-0, or can be homozygous and need transfusions during times of erythroid stress

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20
Q

symptoms of beta thal trait (heterozygote) / minor?

A

usually asymptomatic

may have microcytosis, mild anemia

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21
Q

pathophysiology of iron overload in thalassemia

A

ineffective erythropoiesis and increased iron uptake by gut

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22
Q

complications of thalassemia

A
  • poor growth
  • pain
  • iron overload - cardiac dysfunction, endocrinopathies
  • pigmented gallstones
  • pain as a result of marrow expansion
  • skeletal abnormalities
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23
Q

endocrine effects of thalassemia

A

hypogonadism - due to pituitary iron deposition
hypothyroidism
insulin resistance/diabetes
poor growth

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24
Q

causes of cardiac dysfunction in thalassemia

A 
severe anemia
iron overload
endocrinopathies (diabetes)
pulmonary hypertension
increased cardiac output
vitamin deficiencies due to hypermetabolic state
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25
possible late effects of splenectomy
thrombosis | pulmonary hypertension
26
how does a baby with a three alpha gene deletion present?
hemoglobin A (reduced), hemoglobin H disease (four beta chains), neonatal jaundice, hemolytic anemia
27
how do babies with beta thal present?
may become symptomatic around 6 months of life
28
peripheral film of beta thal or hemoglobin H disease?
microcytosis, hypochromia | bizarre RBC morphology
29
what other changes on hemoglobin analysis might you see with beta thal?
increase hemoglobin F (2alpha+2gamma) and A2 (2alpha+2delta)
30
hallmark of HbH disease?
elevated hemoglobin barts (4gamma) along with hemoglobin H (4beta)
31
what is hemoglobin E?
a mutation of beta globin gene, heterozygotes may have microcytosis and hypochromia. homozygotes have hypo/micro/target cells. minimal anemia.
32
only Hemoglobin F present in newborn?
deletion of delta and beta region | hereditary persistence of fetal hemoglobin
33
inheritance of SCD
autosomal codominant
34
how much hemoglobin S does a heterozygote (AS) have?
35-45% HbS
35
phenotype of alpha thalassemia co-inherited with HbSS?
less anemia, less SS complications
36
genetic cause of HbS
point mutation (A-T) in 6th codon of beta globin gene on chromosome 11, causing a glutamic acid to valine substitution
37
how to differentiate osteoporosis vs VOC as cause of bony pain
ESR hx of bony crisis pain in multiple locations
38
most common cause of death in HbSS
acute chest
39
prevention of ACS?
increased HbF (via HU, prophylactic RBC transfusions)
40
complications of HbSS?
``` VOC ACS stroke (usually ischemic) priapism splenic sequestration aplastic crisis ```
41
stroke prevalence in homozygous HbSS
11% | highest incidence in first decade of life
42
factors associated with increased risk of stroke
``` history of TIA sibling with HbSS and stroke recent ACS / frequent ACS hypertension nocturnal hypoxemia abnormal transcranial doppler ```
43
management of stroke in HbSS
if ischemic - exchange transfusion (goal: reduce HbS to < 30%), followed by chronic transfusion if hemorrhagic - consider chronic transfusion
44
risk of recurrent stroke in HbSS
70% have recurrence within 3 yrs
45
how common is priapism in HbSS
30-45% of males with HbSS 75% of these occur before 20 yrs of age
46
when to go to ED with priapism?
episode > 2 hrs
47
prevention of priapism?
- pseudoephedrine QHS - can try HU (although limited evidence) - leuprolide injections to suppress HPA access consider vasodilating agents (ie, sildenafil) - regular transfusions
48
how to differentiate splenic sequestration vs aplastic crisis?
reticulocytes (elevated in sequestration, suppressed in aplastic crisis)
49
when to consider splenectomy in child with splenic sequestration?
if one major or two minor splenic sequestration episodes
50
end organ damage in HbSS
- cognitive functioning / neuropsych deficits (silent stroke) - cardiovascular function (chronic anemia / increased cardiac output), pulmonary hypertension - chronic lung disease, pulmonary fibrosis, asthma - renal failure - chronic hepatomegaly - pigmented gallstones - avascular necrosis - retinopathy (in HbSC) - adenotonsillar hypertrophy (as a result of loss of splenic tissue)
51
which type of sickle cell is at increased risk of retinopathy
SC
52
causes of death in HbSs
infection with encapsulated organism ACS stroke organ failure
53
how to prevent alloimmunization in child with HbSS
match for Rh and Kell (at minimum)
54
benefit of HU in HbSS
less VOC less ACS reduces mortality
55
dosing of HU
start at 15-20 mg/kg/day, increased Q8weeks until 35 mg/kg/day or favourable response
56
toxicity associated with HU
``` neutropenia thrombocytopenia bone marrow suppression (low retics) stomach upset, headache birth defects (child bearing age women should be on OCP) ```
57
indicators of response to HU
clinical improvement | lab parameters: increase in HbF (typically to 10-20%), rise in Hb of 10-20, increased MCV
58
defining feature of HbC
rhomboid / hexagonal crystals of hemoglobin
59
three things predicting outcome after BMT in patients with thalassemia? name of criteria system?
Pesaro criteria - hepatomegaly > 2cm - liver fibrosis - irregular chelation
60
non blood test ways to measure iron overload
MRI liver / liver biopsy SQUID cardiac T2 MRI

Heme Onc Royal College (30 decks)

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