Microcytic anemias Flashcards
What is hypochromasia?
the red cell central pallor is more than 1/3 of the diameter of the cell
described by a low MCHC (believe it)
What makes red cells small?
decreased membrane or decreased hemoglobin
What is the only congenital cause of decreased red cell membrane?
hereditary elliptocytosis
What is the #1 cause of decreased hemoglobin production?
iron deficiency
What is a common cause of IDA in infants?
women who only give their babies breast milk, which has little to no iron
What are the most common cuases of IDA in men and postmenopausal women?
Gi/GU bleeding most common
malabsorption
inadequate intake
How is iron absorbed?
GI tracT (mostly duodenum), bound to apotransferring to form transferring
that delivers Fe3+ to red cell precusors in the bone marrow
The precusors have transferring receptors on their membranes. where in the cell does the iron go?
can either be used right away or delivered to the mitochodnria for storage (form a rung around the precursor red cell nucleus - why you get sideroblastic rings)
What enzyme is necessary in the mitochdonria to incorporate iron into protoporphyrine to make heme?
ferrochelatase and vitamin B6
IN what form is iron stored in the mitochondria?
ferritin
Where are other locations of iron storage?
1111
What are the classic lab results for IDA?
low RBC
low mCV
low mCHC
high RDW
What’s included in iron studies?
ferritin
transferrin
iron
What will ferritin do in IDA?
expected to be low (because there is not enough iron being stored)
HOWEVER - ferritin is an acute phase reactant and can be falsely elevated into the normal or high range
What would you expect transferrin to do in IDA?
expected to be elevated (because the body will be mobilizing stored iron)
HOWEVER, it can be in the normal range or low when iron deficiency is combined with anemia of chronic disease
Is a serum iron useful in isolation?
No, not at all
Why is a serum iron helpful them?
It can be used to calculate % iron saturation which can be used to interpret the ferritin and transferring levels when confusing or complicated
How do you treat IDA?
oral ferrous sulfate or ferrous gluconate
or parenteral iron dextran
How does anemia of chronic disease happen?
It’s a disorder of iron cycling
chronic inflammation leads to pro-inflammatory cytokines and increased acute-phase reactants that increase plasma viscosity, increase ESR and increase rouleaux and decrease circulating transferring and decreased transferin receptors on the RBC and icnrease delivery of iron to ferritin. So you get all your iron bound to ferritin and not available for cells to use.
What molecule in the liver controlls everything about iron circulating and anemia of chronic disease?
hepcidin (increases ferritin, decreases transferrin, etc.)
A genetic defect in hepcidin causes what disease?
hemochromoatosis
What do the CBC findings look like on anemia of chronic disease?
RBC normal or low Hgb low MCV usually low normal but can be low or very low MCHC can be normal or low RDW can be normal or high
What is the “classic pattern” on iron studies for ACD?
increased ferritin
low transferrin
normal iron saturation (because it’s a relative number)
What are the newer tests for ACD?
soluble transferrin receptor assay (checks for the down-regulated transferrin receptors)
serum or urine hepcidin assay (controversial, but should in theory be elevated)
How do you treat anemia of chronic disease?
treat underlying disorder
recombinant epo
iron suppl
What are the two potential enzymatic defects in heme biosynthesis leading to sideroblastic anemia?
aminolevulinic acid (ALA synthase
ferochelatase
How is sideroblastic anemia diagnosed?
routine CBC with microcytic anemia
iron studies will show a very high ferritin level
blood smear very heplful (hypochromic RBCs with stippling)
What is the defining test for sideroblastic?
iron staining of the bon emarrow
If iron studies are normal for the workup of low mCV, what’s probably going on?
consider a hemoglobin electrophoresis to check for a thalassemia
