Macrocytosis and Macrocytic Anaemia (2)

Question 1

Megaloblastic:
What is seen on Blood film?

What are its causes?

What is it characterised by?

Answer 1

➊ Large RBCs and Hypersegmented neutrophils

➋ • B12 deficiency
• Folate deficiency

➌ Failure to synthesise adequate amounts of DNA

Question 2

Vit B12 deficiency:
Where is it absorbed?
→ What is needed for this?

What are its causes?

What is Pernicious Anaemia?

Answer 2

➊ Terminal Ileum
→ Intrinsic Factor from parietal cells

➋ * ↓Intake - Poor diet, Veganism
* ↑Demand - Haemolysis, HIV, Pregnancy, Growth spurts
* ↓Absorption - Pernicious anaemia, Coeliac, Crohn’a, Gastrectomy/ileal resection, Zollinger-Ellison syndrome, Parasites
* Medication - Alcohol, PPI, H2 antagonists, Metformin
* Congenital - IF deficiency, Cobalamin gene mutation

➍ Autoimmune attack of parietal cells by autoantibodies against IF, which is needed for B12 absorption

N.B. If this co-exists with a folate deficiency, B12 should be replaced first to prevent subacute combined degeneration of the spinal cord (Remember B comes before F). This is because folate metabolism requires B12, therefore further delpleting one of this vitamin.

Question 3

Folate deficiency:
Where is it absorbed?

What are its causes?

Answer 3

➊ Jejunum

➋ • ↑Demand - Pregnancy, Breastfeeding, Growth spurts, Haemolysis, Malignancy, Urinary loss
• ↓Intake - Poor diet, Elderly, Chronic alcohol intake
• ↓Absorption - Methotrexate/Trimethoprim (Folate antagonists), Coeliac disease, Jejunal resection, Tropical sprue

Question 4

What are the causes of Non-megaloblastic macrocytic anaemia?

Answer 4

• Alcohol
• Liver disease
• Hypothyroidism
• Reticulocytosis - ↑Reticulocytes to try and replace the lost RBCs in Haemolytic anaemia or Haemorrhage
• Myelodysplastic syndromes - Type of blood cancer with a lack of healthy blood cells