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23 Cards in this Set

  • Front
  • Back
Epsilon globin is present in ________ until about _____ weeks of gestation.
Embryonal hgb, until about 6 weeks
Alpha globin is present in ________ beginning at _____ weeks of gestation.
Embryonal-->Fetal-->adult beginning around 6 weeks
Gamma globin is present in ______ beginning at ______ weeks of gestation.
Embryonal-->Fetal-->adult beginning at 6 weeks gestation

DECREASES at/near birth (this is a component of fetal Hgb).
Beta globin is present in _____ beginning at ____ weeks of gestation.
Present in embryo-->adult, present at 12 weeks, but increases at/near birth (this is a component of adult Hgb).
What is a thalassemia?
Defect in production of hemoglobin
What is a hemoglobinopathy?
Defect in Hgb fn
Disorders of hemoglobin are due to _______.
DNA mutations (GENETIC)
How does it result in ineffectual erythropoiesis?
Genetic defect causing dec'd gene product and thus:

dec'd/abnl alpha chains
excess gamma chains to dimerize (gamma 4) in infant, and extra beta chains in adult (beta 4)
Form 'pseudohgbs' and precipitate in RBC, causing hemolysis
Stimulates marrow to produce RBCs that don't work and die (ineffectual erythropoiesis)

Hemolysis + marrow expansion-->multisystem dz
Classification based on gene deletion; treatment requirements
aa/aa: normal
aa/a-: mild microcytosis, NO anemia
aa/-- or a-/a-: mild microcytosis, mild anemia; NO TX REQD
a-/--: Hgb H dz; sometimes require transfusion
--/--: Hgb Barts - Hydrops fetalis unless transfused in utero
Hemoglobin Constant Spring:
What is it?
alpha globin variant seen in persons of Asian ancestry; results in elongated globin chain and thalassemic phenotype
Dec'd or abnl beta chains available to dimerize

alpha chains dimerize then tetramize (alpha4) and combine with gamma and sigma chains (elevated Hgb F and A2)

alpha4 globins bind O2 with high affinity and precipitate within reticulocyte, killing cell before it leaves marrow-->ineffectual erythropoiesis (and hemolysis)
Effects, treatment requirements
Degree of effect on beta chains
Differs from alpha-thal classification because not based on gene mutations, but rather on clinical severity.

Thal trait: no anemia; 1 beta chain dysfnal

Thal minor: mild microcytic anemia; 1 beta chain dysfnal, 1 beta chain mutated (but still present)

Thal intermedia: mod microcytic anemia, mostly compensated

Thal major: severe anemia, requires transfusion support; neither of beta chains are fnal
Homozygous alpha-thal vs homozygous beta-thal:
homo alpha-thal: present in utero
homo beta-thal: first year of life (6 mos)
Clinical presentation of beta-thal.
Growth retardation
Frontal Bossing
Maxillary hyperplasia
Why does deletion of all alpha chain genes cause fetal death, but deletion of all beta chain genes do not appear clinically until >4 months of life?
Fetuses and newborns have gamma chains to mop up extra alpha chains to maintain balance
Iron deficiency vs Thalassemia:
Lab values:
Mentzer Index
Serum iron
Both are microcytic, hypochromic anemias

Range of distribution width more elevated in Fe def bc marrow can make large reticulocytes

Mentzer index (MCV/Red cell count):
<12: thalassemia
>13: Fe def anemia

Fe def:
Low serum iron
Low ferritin (stored iron)
High capacity to bind iron (TIBC)
Transfusion therapy:
Effects on beta-thal
Corrects anemia and ineffective erythropoiesis

Rxn, infection
Iron overload!!! --liver deposition leads to cirrhosis; CHF,
Will a patient with a two alpha-chain deletion and a beta-0 thal have more or less severe disease than beta-0 thal alone?
LESS severe due to less of an imbalance of alpha and beta chains

Thalassemia is about imbalance!