Ch. 5 - Macrocytic anemia Flashcards
What is the MCV in macrocytic anemia?
> 100
What are folate and Vit B12 used for that causes anemia?
synth of DNA precursors
What is the form of folate that circulates in the body?
methylated THF
Describe the passage of the methyl group from folate to allow for DNA precursor synth?
methyl-THF to methyl-Vit B12 to homocysteine which then becomes methionine
What is another name for vitamin b12?
cobalamin
What leads to the size of the cells increasing in megaloblastic anemia?
lack of b12 or folate to make DNA keeps the erythroblast from undergoing its last division, so each cell is a little large
Impaired division of granulocytic precursors in megaloblastic anemia leads to (blank)
hypersegmented neutrophils
In what other cells do we see megaloblastic changes?
intestinal cells
in nonmegaloblastic macrocytic anemia, what changes do you NOT see?
hypersegmented neutrophils and megaloblastic changes in cells other than RBCs
Where is folate derived?
green vegetables and some fruits
Where is folate absorbed?
jejunum
How long does it take for folate deficiency to develop? What does this tell us about the body stores?
takes a few months, body stores are minimal compared to vit. b12
What are the three most common causes of folate def?
- poor diet (kids and elderly)2. increased demand (pregnancy, cancer, hemolytic anemia)3. folate antagonists (methotrexate
What enzyme does methotrexate inhibit?
dihydrofolate reductase
how many lobes does a PMN need to be hypersegmented?
more than 5
What are the lab values in folate def for the following:1. serum folate2. serum homocysteine3. serum methylmalonic acid
- decreased serum folate2. increased homocysteine (in both folate and B12 def)3. normal methylmalonic acid (increased for b12)
Glossitis is a finding in (folate/b12/both)
both
What is the dietary source of B12?
complexed with animal protein
What enzyme liberates b12 from the protein complex?
salivary amylase
B12 is bound by R-binder in what part of the body?
in the mouth
Where is intrinsic factor produced? Where does it bind to b12?
made by the parietal cells in the body of the stomach but doesn’t bind to b12 until in the terminal ileum
Where is b12 absorbed?
absorbed complexed to IF in the terminal ileum
How long does it take to develop a b12 def? what does this tell us about the body’s stores of b12?
takes years; liver is loaded with b12
(blank) detaches b12 from R-binder
pancreatic enzymes
how does pancreatic insufficiency cause b12 def. anemia?
no pancreatic enzymes means no separation of b12 from R binder
What is pernicious anemia?
autoimmune destruction of the parietal cells of the stomach and under production of intrinsic factor leading to b12 def. anemia
What diseases cause damage to the terminal ileum that results in b12 megaloblastic anemia?
Crohn’s disease and fish tapeworm Diphyllobothrium latum
T/F: there are hypersegmented PMNs in b12 def. anemia
true
What is the unique clinical finding that separates b12 def from folate def?
subacute combined degeneration of the spinal cord leading to losses in vibratory sensation and proprioception
how does b12 def cause spinal cord damage?
lack of b12 means that methylmalonic acid cannot be converted to Succ-CoA. Methylmalonic acid impairs spinal cord myelinzation
What tract of the spinal cord is used for vibratory sensation?
posterior column
What tract of the spinal cord is used for proprioception?
lateral corticospinal tract
What are the lab values in b12 def anemia for:1. serum b122. serum homocysteine3. methylmalonic acid
- low b122. high homocysteine3. high methylmalonic acid
Where is R-binder and IF resorbed?
terminal ileum
Goat milk can cause a decrease in (b12/folate) absorption
folate
What drugs often inhibit folate uptake?
5-FUMTXTpm-sfxPhenytoinOcp’setoh
Pernicious anemia is seen in what blood group?
Group A
What form of hypersensitivity is pernicious anemia?
type II; autoimmune destruction of parietal cells and Abs that block B12-IF binding
T/F: anemia is not necessarily present with nonmegaloblastic macrocytosis
true
