hemoglobinopathies Flashcards
what type of inheritance pattern is sickle cell anemia?
autosomal recessive disorder
what are sickle cells
deoxygenated hemoglobin that forms long polymers
-block vessels causing pain crises and tissue infarction especially the marrow and spleen
what causes moderate to severe hemolytic anemia?
repeated sickling crises
describe normal adult hemoglobin
> 95% HbA
<4% HbA2
<1% fetal hemoglobin
HbA
a2B2
HbA2
a2δ2
HbF
a2Y2
in sickle cell disease, B-globin chain has a point mutation at the 6th codon that causes what change?
glutamate to valine
sickle cell disease vs sickle cell trait
disease is homozygous-symptomatic
trait is heterozygous, asymptomatic
what percent of Africans are heterozygous for HbS?
up to 30%
what does the sickle cell trait protect from?
malaria falciparum
what percentage of African Americans have sickle cell trait?
8-10%
what percentage of African Americans have sickle cell disease?
0.17%
what are the complications that arise from vaso-occlusive crisis?
-pain crisis
-chronic hypoxia
-infarction (tissue death bc of lack of blood)
-acute chest syndrome-lung infection
-stroke
-sequestration crisis- in spleen of children
-aplastic crisis - parvovirus B19 (body stops making blood cells)
what are the clinical course that can cause vaso-occlusive complications?
-genetic
-cigarette smoke, respiratory infection, hydration, high altitude
at what age does complete splenic autoinfarction occur in sickle cell disease patients?
by age 20
what type of infections are SCD patients susceptible to?
encapsulated organisms bc the spleen is impaired and can’t remove them
Sickledex test
-screening test for sickle cell anemia
-mix blood with matebodulfite (reducing agent)—>sickling
-does not distinguish disease from trait