Vit B12 and folic acid deficiency Flashcards
What is the alternative name for vit B12?
Cobalamin
What is the role of VitB12?
DNA synthesis
Maintaining nervous system integrity
What is the main dietary source of folic acid?
Leafy greens
What is the role of folic acid in haematopiesis?
DNA synthesis
What is the role of folic acid in biochemical pathways in the body?
Homocysteine metabolism to methionine
What is the main consequence of defective homocysteine metabolism?
CVD
What roles do vit B12 and folic acid play in DNA synthesis?
dMTP synthesis:
B12 acts as a cofactor for methionine synthetase
Recall some dietary sources of B12
Meat, salmon, cod, dairy products, eggs
Recall the full pathway of B12 absorption
In stomach binds to transcobalamin 1
Gastric parietal cells produce IF
B12 displaced from transcobalamin 1 in intestine
B12 binds IF –> terminal ileum
B12-IF complex binds receptor –> circulation
In circulation B12 binds transcobalamin 2
Recall the full pathway of folic acid absorption
Hydrolysed in stomach due to low pH –> monoglutamates
Absorbed as pteroglutamates
Recall 3 causes of B12 deficiency
Vegan diet
GI surgery
IBD
Recall 3 reasons why folic acid absorption might be impaired
Coeliac
IBD
Drugs
Recall 3 reasons why folic acid requirement might be increased
Pregnancy
Malignancy
Haemolytic anaemia
What sorts of anaemia are caused by B12 deficiency?
Macrocytic and megaloblastic
Other than anaemia, what is a key clinical feature of B12 deficiency?
Neurological problems due to demyelination
Describe the shape of macrocytes in vit B12/ folic acid deficiency
oval
How is the MCV affected by megaloblastic aneamia and why?
Drops
Morphological change of erythrocyte within bone marrow
Recall the 6 stages of development of an erythrocyte
Proerythroblast Basophillic erythrocyte Polychromatic erythrocyte Pyknotic erythrocyte Reticulocyte Erythrocyte
Describe the structure of a proerythroblast
Large space in middle = uncondensed chromatin
Why are red cell precursors increased in sixe in megaloblastic anaemia?
Defects in DNA synthesis –> asynchronous maturation of cytoplasm and nucleus
What is the origin of hypersegmented neutrophils?
Giant metamyelocytes in bone marrow due to defective DNA synthesis
What would be seen alongside erythrocytes in the blood film of someone with B12 deficiency?
Fragments of red cells
What is the gold standard test for diagnosis of B12/ folic acid deficiency, and what is a positive result?
Plasma homocysteine
High
How can B12 deficiency be treated?
Injections
