According to Goljan: "B12 (cobalamin) has cobalt in it. Circulating form of folate is methyltetrahydrofolate. Purpose of cobalamin (B12) is to take the methyl group off of methyltetrahydrofolate. Then it’s called tetrahydrofolate. If you don’t get the methyl group off of folate, you will not make DNA. So, if you are B12 def, you can’t get the methyl group off and cannot make DNA. If you are def in folate, you can’t make DNA."
Although Crohn's may have ulcers, fistulas, and bleeding; it usually does not cause iron deficiency anemia and has less bleeding than UC. "Structural abnormalities of the terminal ileum, such as Crohn disease and surgical resection, can cause decreased absorption of vitamin B12." - First Aid General Principles
Why would it not be anemia of chronic disease with decreased serum transferrin concentration?
folic acid when it enters the body is in the form of methyltetrahydrofolate (THF methylated). It donates its methyl group to vitamin B12 to become THF (the active form which as a DNA precursor). The vitamin B12 with its methyl group goes on to combine with homocyteine to form methionine.
macrocytic anemia (seen in blood smear) = RBC precursors can grow but not divide
oval macrocytes (seen in blood smear) = megaloblastic anemia (if they don't show neutrophil hypersegmentation)
B12 has neurologic symptoms and low methylmalonic acid while folate deficiency does not
folate is absorbed in jejunum, B12 in ileum
causes of B12 deficiency = pernicious anemia, gastrectomy, ileal resection, fish tapeworm, veganismD) failure of MTHFR --> THF (via methyltransferase = B12 deficiency and macrocytic anemia
B) G6PD deficiency = normocytic because of incr RBC destruction; pt would show intravascular hemolysis sx precipitated by an oxidative stressor
C) protoporphyinogen oxidase deficiency = microcytic anemia because of low heme synthesis
A) decr transferrin = high ferritin = anemia of chronic disease = microcytic anemia because of low iron
Was about to choose decreased transferrin because I couldn't see hyper-segmented neutrophils. But NBME often tries to throw us off with vague images. So I read again. Caught the "Ileal resection". Iron Fist Bro! Ileum is B12 absorption. B12 results in megaloblastic anemia. N5-MTHF is a step in converting DHF into THF. Inhibited in megaloblastic anemia like B12 and B9 def.
how to rule out iron def. ? iron is absorbed in deodenum and proximal jejunum .
b12 in ileum.
this will give you the answer
submitted by ∗syoung07(58)
would have been real neato if they threw in a hyper-segmented neutrophil