Vitamin B12 + Folate Deficiency Flashcards
What is megaloblastic anaemia?
Anaemia caused by vit B12 or folate deficiency
How does B12 or folate cause anaemia?
Deficiency in building blocks for DNA synthesis
Where does vitamin B12 come from?
Foods of animal origin
How is vitamin B12 absorbed?
Binds to haptocorrin - released by salivary glands
In small intestine - released from haptocorrin + binds to intrinsic factor
IF-B12 complex binds to receptors in terminal ileum
In portal blood B12 binds to transcobalamin II
Where is intrinsic factor produced?
Parietal cells in the stomach
What can cause low B12?
Dietary deficiency
Lack of intrinsic factor
Ileum disease
Lack of transcobalamin
What is pernicious anaemia?
Autoimmune disease affecting gastric parietal cells causing lack of intrinsic factor
Where is folate absorbed?
Duodenum
Jejunum
What can cause folate deficiency?
Dietary deficiency
Increased use
Disease of duodenum/jejunum
Lack of methylTHF
What causes increased use of folate?
Pregnancy
Increased erythropoiesis
Severe skin disease
What is the function of folate?
Converted to methylTHF
MethylTHF essential for
- serine-glycine conversion
- histidine catabolism
- purine synthesis
- thymidylate synthesis
What is the function of B12?
Transfer methyl group to form succinyl-CoA
Transfer methyl group to methionine
How does B12/folate deficiency cause anaemia?
Thymidylate deficiency
- uracil incorporated into DNA instead
- DNA destroyed
What does a blood film show in megaloblastic anaemia?
Macrocytic red cells
Anisopoikilocytosis with tear drops
Hypersegmented neutrophils
How is folate deficiency managed?
Oral folic acid
