3. Sickle Cell Disease Flashcards

1
Q

life expectancy of scd

A

uk = 40-60yrs
devleoping nations = 50-90% childhood mortality

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2
Q

balanced polymorphism

A
  • multiple alleles of a gene are maintained in a population
  • one version will have an advantage compared to the other
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3
Q

genetic cause of scd

A

A->T
glutamic acid –> valine on 6th position of beta globin chain

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4
Q

name of heterozygous and homozygous states

A

het = HbAS
homo = HbSS

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5
Q

frequency of HbAS in malarial areas

A

up to 40%
provides protection

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6
Q

one major theory as to why HbAS provides malarial protection

A
  • their sickle Hb has altered interaction with actin in a RBC
  • means RBC cytoskeleton is altered
    = ‘sticky’
    -These changes may impair parasite-induced remodelling of the red blood cell surface membrane
  • means they cant complete their life cycle efficiently
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7
Q

difference between glutamine and valine

A

glu is + charged
(so moelcules repel each other)
val is neutral (acc promotes interaction)

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8
Q

when and why does valine cause Hb to stick together

A
  • Hb is deoxyegnated
    = valine exposed on Hb surface
  • now can interact cuz valine neutral charge
  • forms long fibrous linked chains
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9
Q

how come most dont have sickling all the time

A
  • process of sickling takes time
  • most cells return to lung and get o2nated before major sickling occurs
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10
Q

how come foetuses are chilling

A

foetal Hb is not affected
sickling only happens after delivery

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11
Q

what is a coinherited factor that can decrease disease severity

A

hereditary persistence of foetal haemoglobin (HPFH)

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12
Q

CHRONIC DAMAGE: Hb

A

repeated cycles of polym damages Hb
eventually polym starts to prolong
and doesnt reverse = Hb denatures

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13
Q

CHRONIC DAMAGE: cells

A

repeated cycle of cell shape change damages cell
- causes partial shape change
- memb pumps damaged = cell dehydrated

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14
Q
A
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15
Q

4 types of cell appearances

A
  • boat cells = partial sickle change
  • target cells = Hb pool
  • dehydrated dense and irregular damaged (MOST COMMON)
  • true sickle cells = irreversible sickling
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16
Q

Hb levels in scd compared to normal

A

70-80g/l
compared to
130-140g/l

17
Q

ACUTE CRISIS: what can cause sickling to happen faster

A

hypoxia, fever, dehydration
(reverse of these would be needed for treatment)

18
Q

ACUTE CRISIS: blocking small vessels

A

spiky, sticky cells = no torpedo shape
increases hypoxia and the more sickling

19
Q

4 types of acute crisis

A
  • bone pain and damage
  • stroke
  • chest crisis
  • sepsis