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Heme Onc Royal College > Hemoglobinopathies > Flashcards

Hemoglobinopathies Flashcards

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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
Q

possible late effects of splenectomy

A

thrombosis

pulmonary hypertension

26
Q

how does a baby with a three alpha gene deletion present?

A

hemoglobin A (reduced), hemoglobin H disease (four beta chains), neonatal jaundice, hemolytic anemia

27
Q

how do babies with beta thal present?

A

may become symptomatic around 6 months of life

28
Q

peripheral film of beta thal or hemoglobin H disease?

A

microcytosis, hypochromia

bizarre RBC morphology

29
Q

what other changes on hemoglobin analysis might you see with beta thal?

A

increase hemoglobin F (2alpha+2gamma) and A2 (2alpha+2delta)

30
Q

hallmark of HbH disease?

A

elevated hemoglobin barts (4gamma) along with hemoglobin H (4beta)

31
Q

what is hemoglobin E?

A

a mutation of beta globin gene, heterozygotes may have microcytosis and hypochromia. homozygotes have hypo/micro/target cells. minimal anemia.

32
Q

only Hemoglobin F present in newborn?

A

deletion of delta and beta region

hereditary persistence of fetal hemoglobin

33
Q

inheritance of SCD

A

autosomal codominant

34
Q

how much hemoglobin S does a heterozygote (AS) have?

A

35-45% HbS

35
Q

phenotype of alpha thalassemia co-inherited with HbSS?

A

less anemia, less SS complications

36
Q

genetic cause of HbS

A

point mutation (A-T) in 6th codon of beta globin gene on chromosome 11, causing a glutamic acid to valine substitution

37
Q

how to differentiate osteoporosis vs VOC as cause of bony pain

A

ESR
hx of bony crisis
pain in multiple locations

38
Q

most common cause of death in HbSS

A

acute chest

39
Q

prevention of ACS?

A

increased HbF (via HU, prophylactic RBC transfusions)

40
Q

complications of HbSS?

A 
VOC
ACS
stroke (usually ischemic)
priapism
splenic sequestration
aplastic crisis
41
Q

stroke prevalence in homozygous HbSS

A

11%

highest incidence in first decade of life

42
Q

factors associated with increased risk of stroke

A 
history of TIA
sibling with HbSS and stroke
recent ACS / frequent ACS
hypertension
nocturnal hypoxemia
abnormal transcranial doppler
43
Q

management of stroke in HbSS

A

if ischemic - exchange transfusion (goal: reduce HbS to < 30%), followed by chronic transfusion

if hemorrhagic - consider chronic transfusion

44
Q

risk of recurrent stroke in HbSS

A

70% have recurrence within 3 yrs

45
Q

how common is priapism in HbSS

A

30-45% of males with HbSS

75% of these occur before 20 yrs of age

46
Q

when to go to ED with priapism?

A

episode > 2 hrs

47
Q

prevention of priapism?

A
  • pseudoephedrine QHS
  • can try HU (although limited evidence)
  • leuprolide injections to suppress HPA access
    consider vasodilating agents (ie, sildenafil)
  • regular transfusions
48
Q

how to differentiate splenic sequestration vs aplastic crisis?

A

reticulocytes (elevated in sequestration, suppressed in aplastic crisis)

49
Q

when to consider splenectomy in child with splenic sequestration?

A

if one major or two minor splenic sequestration episodes

50
Q

end organ damage in HbSS

A
  • 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
Q

which type of sickle cell is at increased risk of retinopathy

A

SC

52
Q

causes of death in HbSs

A

infection with encapsulated organism
ACS
stroke
organ failure

53
Q

how to prevent alloimmunization in child with HbSS

A

match for Rh and Kell (at minimum)

54
Q

benefit of HU in HbSS

A

less VOC
less ACS
reduces mortality

55
Q

dosing of HU

A

start at 15-20 mg/kg/day, increased Q8weeks until 35 mg/kg/day or favourable response

56
Q

toxicity associated with HU

A 
neutropenia
thrombocytopenia
bone marrow suppression (low retics)
stomach upset, headache
birth defects (child bearing age women should be on OCP)
57
Q

indicators of response to HU

A

clinical improvement

lab parameters: increase in HbF (typically to 10-20%), rise in Hb of 10-20, increased MCV

58
Q

defining feature of HbC

A

rhomboid / hexagonal crystals of hemoglobin

59
Q

three things predicting outcome after BMT in patients with thalassemia? name of criteria system?

A

Pesaro criteria

  • hepatomegaly > 2cm
  • liver fibrosis
  • irregular chelation
60
Q

non blood test ways to measure iron overload

A

MRI liver / liver biopsy
SQUID
cardiac T2 MRI

Heme Onc Royal College (30 decks)

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