5 - Sideroblastic and Megaloblastic Anemia Flashcards
size of RBCs in sideroblastic anemia
microcytic
3 general etiologies of microcytic anemias
iron deficiency
defects in porphyrin (sideroblastic anemia)
defects in globin - thalassemias
sideroblastic anemias are due to defects in
porphyrin ring
ringed sideroblast
pathologic finding in bone marrow - large blocks of iron stained with Prussian Blue indicating buildup of iron since porphyrin is defective and can’t incorporate it
key histo finding in sideroblastic anemia
RINGED sideroblast (plain sideroblasts are normal)
congenital sideroblastic anemia inheritance pattern
most often x linked, but can also be autosomal recessive or mitchondrial
relationship between congenital sideroblastic anemia and porphyrias
both are defects in porphyrin synthesis - sideroblastic anemia is defect in first step, porphyrias are in later steps and produce backup of toxic intermediates
enzyme deficient in congenital sideroblastic anemia
delta aminolevulinic acid synthase (delta ALA synthase)
some pts with congenital sideroblastic anemia improve when given ___ because ___
pyridoxine, it is a cofactor of the deficient enzyme
causes of acquired sideroblastic anemia (5)
alcohol (depletes pyridoxine) lead copper deficiency (2/2 past gastric bypass, zinc in denture adhesives; also presents w/ peripheral neuropathy) INH (TB drug) chloramphenicol
what clue can you see in PBS in pt w/ lead induced sideroblastic anemia?
coarse basophilic stipling (fine basophilic stipling could just be a retic)
acquired sideroblastic anemia can also be a part of what syndrome?
myelodysplastic syndrome
blood work findings in acquired sideroblastic anemia as part of myelodysplastic syndrome:
serum iron?
% sat w/ iron?
ferritin?
inc serum iron
inc % sat
high ferritin
general tx of siderblastic anemia
pyridoxine, transfusions if severe
why would the MCV in acquired sideroblastic anemia not be low?
often have 2 distinct populations of cells - micro and macrocytic, average out to normal-ish MCV
mechanism behind megaloblastic anemia
DNA synth impaired > arrest cell division while cytoplasm continues to grow > macrocytosis
main causes (2) of megaloblastic anemia
B12 and folate deficiency
other findings in PBS with megaloblastic anemia (besides macrocytosis) (3)
hypersegmented neutrophils
oval shaped cells
Howell Jolly bodies (small basophilic spot in mature erythrocyte)
cobalamin (B12) deficiency results in increase in ____ and ____ (chemicals)
methylmalonic acid and homocysteine
absorption of B12
binds to haptocorrin (from saliva) in stomach
GIF (from parietal cells) grabs B12 in duodenum
absorbed in ileum
B12 exported into plasma and binds transcobalamin
absorption of B12 is inhibited by what common drug?
metformin
pernicious anemia
autoimmune attack on parietal cells
also get blocking anti GIF antibodies
decreased B12 absorption
clinical manifestations of B12 deficiency
megaloblastic anemia (ineffective erythropoiesis and increased apoptosis) thrombocytopenia leukopenia cardiomyopathy pale "lemon yellow" skin gastric atrophy / CA glossitis combined systems degeneration
lab values indicating b12 deficiency
inc LDH low haptoglobin inc MMA, homocysteine serum iron often inc TIBC normal, % sat inc ferritin inc
main way to tell B12 deficiency from folate clinically
folate has no neuro sx
causes of folate deficiency
nutritional dialysis celiac gastric bypass IBD pregnancy hemolysis drugs/ETOH
main way to tell B12 deficiency from folate from bloodwork (other than just measuring vitamin levels..)
folate > inc homocysteine
B12 > inc homocysteine AND MMA
less common causes of megaloblastic anemia
nitrous oxide
drugs (methotrexate, hydroxyurea, DNA synth inhibitors, anti convulsants, oral contraceptives)
inborn errors of metabolism
myelodysplastic syndrome
