Flashcards in Vit B12 and folic acid deficiency Deck (22)
What is the alternative name for vit B12?
What is the role of VitB12?
Maintaining nervous system integrity (involved in myelination)
What is the main dietary source of folic acid?
What is the role of folic acid in haematopiesis?
What is the role of folic acid and B12 in biochemical pathways in the body?
Homocysteine metabolism to methionine
What is the main consequence of defective homocysteine metabolism?
CVD (main increased risk)
Homocysteine aggravates atherosclerosis and premature vascular diseases, leading to the above 2 problems
What roles do vit B12 and folic acid play in DNA synthesis?
B12 acts as a cofactor for methionine synthetase
Recall some dietary sources of B12
Meat, salmon, cod, dairy products, eggs
How is B12 absorbed?
Method 1: straight through Duodenum (slow and inefficient)
Method 2: Most common method
1. Binds to IF in stomach produced by parietal cells
2. B12-IF complex binds to receptors in terminal ileum
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
Diet: Vegan diet
Malabsorption: pernicious anaemia, GI surgery, coeliac disease, Crohn's
Infections: H pylori, Giardia
Drugs: Metformin, oral contraceptives, PPI eg omeprazole
Recall 3 reasons why folic acid absorption might be impaired
Recall 3 physiological and 3 pathological reasons why folic acid demand would be increased
Adolescence- period of rapid growth
Premature babies- grow quickly and they can become deficient of Folate
Malignancy- turnover of extra cells
Erythoderma – massive turnover of skin cells
Haemolytic anaemias – increased RBC turnover
What sorts of anaemia are caused by B12 deficiency?
B12 deficiency will lead to Macrocytic and megaloblastic erythrocytes. It is called pernicious anaemia if the B12 deficiency is caused by Autoimmune attack on parietal cells which produce IF
Other than anaemia, what is a key clinical feature of B12 deficiency?
Neurological problems due to demyelination
-Bilateral peripheral neuropathy
-Subacute combined degeneration of the cord
Describe the shape of macrocytes in vit B12/ folic acid deficiency
How is the MCV affected by megaloblastic aneamia and why?
Morphological change of erythrocyte within bone marrow
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?