263b sickle cell Flashcards

1
Q

hemoglobin - what globin chains are present in adults? what is in each chain?

A

HbA = a2,b2 (97%)
HbA2=a2d2 (3%)
HbF=a2g2 (increased with hydroxyurea)

heme = Fe + protoporphyrin: can bind O2, CO when reduced (Fe 2+)

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2
Q

where are the two globin gene?

A

a - chromosome 16

b - chromosome 11

arranged in order of globin production during life

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3
Q

hemoglobin switching

A

10 weeks: E (embryo) –> gama

birth-6 months: gamma –> B

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4
Q

SCD mutation?

A

HbS point mutation in B chain

G –> V single amino acid replacement at position 6.

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5
Q

SCD pathogenesis?

A

Pathogenesis: low O2, dehydration, or acidosis ->

sickling (deoxygenated HbS polymerizes) –>

anemia and vaso-occlusive disease.

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6
Q

SCD - newborn presentation? heterozygote advantage? AA carriers?

A

Newborns are initially asymptomatic (high HbF and low HbS)

Heterozygotes (sickle cell trait) have resistance to malaria (homozygous will kill you though –> example of balanced polymorphism)

8% of African Americans carry the HbS trait

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7
Q

Sickle cell - skull x-ray appearance?

A

“Crew cut” on skull x-ray due to marrow expansion from increased erythropoiesis (also in thalassemias).

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8
Q

SCD - treatment?

A

hydroxyurea (increases HbF)

bone marrow transplantation.

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9
Q

SCD - hydration of RBC?

A

dehydrated because increased K efflux and KCl- cotransport efflux –> efflux of H2O –> irreversible sickling

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9
Q

SCD - painful crisis presentation?

A
dactylitis (painful hand swelling)
acute chest syndrome (most common cause of death in adults)
avascular necrosis
stroke (5-10 years old)
severe back pain

acute chest syndrome = fever + abnormal CXR + respiratory syndrome

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9
Q

SCD - complications?

A

aplastic crisis w/ parvovirus B19

autosplenectomy (increased encapsulated bacteria infection risk)

splenic sequestration crisis

salmonella osteomyelitis

painful crisis (vaso-occlusive) - RBC stick, WBC and platelets interact and are activated, NO gets depleted

renal papillary necrosis

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