Macrocytic Anemia Flashcards
three pathological mechanisms of macrocytosis
too many immature RBC
membrane too large for Hb content
defect n DNA synthesis and nucleus of erythrobast divides fewer times than cyto
not real macrocytosis, but will read that way
shifting of immature cells from marrow–>peripheral blood (reticulocytosis)–this is considered NONmegaloblastic
Megaloblastic anemias
B12 def
folate def
medications (azt, hydroxyurea)
reticulocytoss
action of epo to correct anemia causes RBC to skip divisons in an effort to push out into periphery
vitamin b12 and folate
required for thymdylate and purine synthesis therefore their deficiency result in retarted DNA synthesis
RNA synthesis
even though DNA synthesis is impared, RNA synthesis is unaffected–>more cytoplasmic components in a slowly dividing cell
vit b12 rxn (2)
Vit B12 + homocysteine–> THF –>methionine–> purines/pyrmidines
formation of succinyl coa
blocking vitamin b12 leads to excess
MMA, homocysteine
b12 deficency by
cannot be produced by human body and only comes from animal byproducts (so vegans have issues)..takes a long time to develop
vit b12 absorption mech
in stomach binds to HAPTOCOIRIN–>in duo pancreatic proteases cleave–>binds to IF which is released by parietal cells–>absorbed by terminal ileum
defect in intrinsic factor
pernicious anemia
–autoantibodies to gastric pareital cells which make intrinsic factor
effects of vitamin B12 deficiency
hematological effects- anemia and pancytopenia
neurological disorders- gait/paresthesias/numbness, cog disorders (due to demyelin)
developmental effects
schilling test
check to see if vit b12 is due to lack of intrinsic factor
treatment B12 deficiency
inject B12 supplementation
-high dose oral sometimes an option– daily/weekly at first than monthly
sources of folate
leafy vegetables – spinach, turnip greens, lettuces, dried beans, peas, cereal, sunflower seeds
