Anaemia - Vitamin B12 Deficiency

Question 1

Outline the epidemiology of Vitamin B12 deficiency anaemia (2).

Answer 1

Main demographic:
* People from developing countries
* Older people

Question 2

What are the risk factors of Vitamin B12 deficiency anaemia (6)?

Answer 2

• Age > 65 years
• Gastric surgery (bypass or resection)
• Chronic gastrointestinal (GI) disease
• Vegan diet
• Metformin use
• H2 receptor antagonist or proton-pump inhibitor use

Question 3

Outline the pathogenesis of Vitamin B12 deficiency anaemia (3).

Answer 3

• Decreased dietary intake
• Diminished gastric breakdown of vitamin B12 from food
• Malabsorption from the gastrointestinal tract

Question 4

Outline the pathophysiology of Vitamin B12 deficiency anaemia (3).

Answer 4

1. Both folate and vitamin B12 (cobalamin) are cofactors in methylation of homocysteine to form methionine
2. Therefore, deficiency of either vitamin increases homocysteine (a biomarker of folate deficiency)
3. NADPH reduces glutathione, which mitigates oxidative stress in rapidly dividing cells.

Question 5

How would a patient with Vitamin B12 deficiency anaemia present (4)?

Answer 5

Hx of:
* Risk factors
* Gastric surgery (gastrectomy, or bypass for obesity)

Common:
* Old age
* Paraesthesias

Uncommon:
* Vegan and strict vegetarian diet
* Chronic gastrointestinal disease (e.g., Crohn’s disease or coeliac disease)
* Medicine (proton-pump inhibitors, H2 receptor antagonists, metformin, anticonvulsants)
* Ataxia
* Decreased vibration sense
* Positive Romberg’s test
* Pallor
* Petechiae
* Glossitis
* Angular cheilitis
* Cognitive impairment

Question 6

What investigations are recommended in suspected Vitamin B12 deficiency anaemia (4)?

Answer 6

• Peripheral blood smear
• FBC
• Serum vitamin B12
• Reticulocyte count

Question 7

What would is the diagnostic result of FBC in Vitamin B12 deficiency anaemia?

• Hb
• MCH
• MCV
• Platelet
• WBC count

Answer 7

• Hb: reduced
• MCH: elevated
• MCV: elevated
• Platelet: normal
• WBC count: normal

Low haematocrit

Question 8

What would is the diagnostic result of peripheral blood smear in Vitamin B12 deficiency anaemia?

Answer 8

Megalocytes, hypersegmented polymorphonucleated cells

Megaloblastic macrocytic anaemia: A. Peripheral blood smear of a patient with megaloblastic anaemia. B. Peripheral blood smear of healthy individual

Question 9

What would is the diagnostic result of reticulocyte count in Vitamin B12 deficiency anaemia?

Answer 9

Low

Question 10

What would is the diagnostic result of serum vitamin B12 in Vitamin B12 deficiency anaemia?

Answer 10

Low

Question 11

What is the management of a symptomatic patient with Vitamin B12 deficiency anaemia (1 + 2)?

Answer 11

Parenteral cyanocobalamin or Hydroxocobalamin

Adjuvant:
* Blood transfusion ± diuretic
* Oral folic acid

Question 12

What is the management of a asymptomatic patient with Vitamin B12 deficiency anaemia (1)?

Answer 12

Dietary supplementation + multivitamins