Vit B12/ folate deficiency

Question 1

What is the role of B12 in the body?

Answer 1

1. Synthesize DNA precursor thymidine (needed for cell division0 role in RBC formation and myelination of the Nervous system)
2. Decreases harmful chemicals: homocysteine and methylmalonic acid:

B12 is also:
- Present in animal products
- Absorbed in the terminal ileum and requires intrinsic factor (IF)

Question 2

What are some of the causes of V12 deficiency?

Answer 2

Impaired absorption:
1. Pernicious Anaemia (most common cause) → autoantibodies against IF (needed for B12 absorption) or gastric parietal cells. Increases risk of gastric cancer. May have history of autoimmune disease.
2. Post Gastrectomy
3. Terminal Ileum Affected → crohn’s disease or ileocaecaecal resection
Decreased dietary intake:
1. Vegan Diet (& not taking supplements)

Question 3

What are harmful consequences of homocysteine and methylmalonic acid?

Answer 3

TOO MUCH of

1. homocysteine:
   - increases risk of atherosclerosis; ischaemia of tissues
   - promotes clotting; increases risk of heart disease & stroke
2. Methylmalonic acid:
   - accumulates in the axon of neurons & causes damage; impaired neurological & muscle function

Question 4

What is the role of vitamin B9/ folic acid?

Answer 4

Essential coenzyme that enables critical biochemical reactions for DNA synthesis and amino acid metabolism
- Sources → green leafy vegetables, fruits, liver, bread, cereal

Question 5

What are the causes of Vitamin B9 deficiency?

Answer 5

1. malabsorption (small bowel disease due to IBD or coeliac disease)
2. malnutrition (chronic alcohol use)
3. increased requirement (pregnancy)
4. drug related (methotrexate, antiepileptics)

Question 6

What are the signs/ symptoms of Vit B12/ folate deficiency?

Answer 6

1. Vitamin B12 →
   - signs of anaemia (fatigue, pallor, SOB), peripheral neuropathy (tingling, numbness, paraesthesia), dementia, glossitis (may present as sore tongue)
2. Folate →
   - signs of anaemia (fatigue, pallor, SOB), glossitis, fetal spina bifida (neural tube defects) if maternal deficiency
   - Unlike vitamin B12 deficiency, folate deficiency does not result in neurological symptoms.

Question 7

What investigations are used to diagnose/ monitor vit B12/ folate deficiency?

Answer 7

1. Signs of Macrocytic, Megaloblastic Anaemia → decreased Hb, increased MCV, hyperchromic RBCs, hypersegmented neutrophils
2. Vitamin B12 (pernicious anaemia) → test for autoantibodies (anti-IF or antiparietal cell)
   - Intrinsic Factor antibodies are more specific
3. Homocysteine → elevated in B12 & Folate deficiency
4. Methylmalonic Acid (MMA) → elevated in B12 deficiency, normal in folate deficiency

Question 8

How is vit B12/ folate deficiency managed?

Answer 8

1. Vitamin B12 → IM supplementation of vitamin B12 (hydroxocobalamin)
2. Folate → oral folate supplementation, nutritional counseling to increase folate intake
   - Should also be given to pregnant women due to risk of neural tube defects (spina bifida and anencephaly)
   - 400mcg of folic acid until the 12th week of pregnancy

Always replace vitamin B12 before folate - protects against subacute combined degeneration of the cord

Question 9

What complications may arise following vitamin B12/ folate deficiency?

Answer 9

1. Peripheral neuropathy & subacute degeneration of the spinal cord (predominantly affects dorsal columns) 
2. Increased risk of gastric cancer (pernicious anaemia) 
3. Impaired cell division
4. Macrocytosis = destruction of RBC = anaemia = bone marrow releases abnormally developed RBC precursors (megaloblasts) = megaloblastic anaemia.
5. Bone marrow releases large, immature neutrophils with hypersegmented nuclei.
6. Pancytopenia (Low RBC, WBC, platelets)
7. Glossitis (swollen tongue; epithelial cells arent replaced)