Vit B12 and folic acid deficiency Flashcards Preview

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Flashcards in Vit B12 and folic acid deficiency Deck (22)
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1

What is the alternative name for vit B12?

Cobalamin

2

What is the role of VitB12?

DNA synthesis
Maintaining nervous system integrity (involved in myelination)

3

What is the main dietary source of folic acid?

Leafy greens

4

What is the role of folic acid in haematopiesis?

DNA synthesis

5

What is the role of folic acid and B12 in biochemical pathways in the body?

Homocysteine metabolism to methionine

6

What is the main consequence of defective homocysteine metabolism?

CVD (main increased risk)
Venous/Arterial thrombosis

Homocysteine aggravates atherosclerosis and premature vascular diseases, leading to the above 2 problems

7

What roles do vit B12 and folic acid play in DNA synthesis?

dTMP synthesis:
B12 acts as a cofactor for methionine synthetase

8

Recall some dietary sources of B12

Meat, salmon, cod, dairy products, eggs

9

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
3. Absorbed

10

Recall the full pathway of folic acid absorption

Hydrolysed in stomach due to low pH --> monoglutamates
Absorbed as pteroglutamates

11

Recall 3 causes of B12 deficiency
Diet
Malabsorption
Infections
Drugs

Diet: Vegan diet
Malabsorption: pernicious anaemia, GI surgery, coeliac disease, Crohn's
Infections: H pylori, Giardia
Drugs: Metformin, oral contraceptives, PPI eg omeprazole

12

Recall 3 reasons why folic acid absorption might be impaired

Coeliac
IBD
Drugs

13

Recall 3 physiological and 3 pathological reasons why folic acid demand would be increased

PHYSIOLOGICAL
Pregnancy
Adolescence- period of rapid growth
Premature babies- grow quickly and they can become deficient of Folate
PATHOLOGICAL
Malignancy- turnover of extra cells
Erythoderma – massive turnover of skin cells
Haemolytic anaemias – increased RBC turnover

14

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

15

Other than anaemia, what is a key clinical feature of B12 deficiency?

Neurological problems due to demyelination
eg
-Bilateral peripheral neuropathy
-Subacute combined degeneration of the cord
-optic atrophy
- dementia

16

Describe the shape of macrocytes in vit B12/ folic acid deficiency

oval

17

How is the MCV affected by megaloblastic aneamia and why?

Drops
Morphological change of erythrocyte within bone marrow

18

Why are red cell precursors increased in sixe in megaloblastic anaemia?

Defects in DNA synthesis --> asynchronous maturation of cytoplasm and nucleus

19

What is the origin of hypersegmented neutrophils?

Giant metamyelocytes in bone marrow due to defective DNA synthesis

20

What would be seen alongside erythrocytes in the blood film of someone with B12 deficiency?

Fragments of red cells

21

What is the gold standard test for diagnosis of B12/ folic acid deficiency, and what is a positive result?

Plasma homocysteine
High

22

How can B12 deficiency be treated?

Injections