Definition & Etiology
Definition
- Metabolic anaemia with elevated MCV (>100) – Can be:
- Vitamin B12 & folate deficiency, Drug-induced (Use blood methotrexate film to help toxicity)
- non-megaloblastic – Pregnancy, Hypothyroidism, Alcohol abuse
Etiology
B12 Deficiency:
- Pernicious anaemia (autoimmune): gastric mucosal destruction (ß intrinsic factor), antiparietal cell antibodies, more common in women >60 years, increased risk of gastric cell cancer
- Dietary: vegan diet/ malnutrition
- Intestinal: malabsorption, ileal resection, Crohn’s
- Inherited: intrinsic factor receptor deficiencies (Imerslund-Grasbeck syndrome)
- Gastric: total/partial gastrectomy, congenital intrinsic factor deficiencies, Zollinger-Ellison syndrome
- Drugs: PPIs, H2 receptor antagonists, colchicine, nitrous oxide, metformin
Folate Deficiency:
- Dietary: poor diet, alcoholism
- Liver disease
- Excess urinary excretion
- Increased requirements: malignancy, pregnancy, blood disorders
- Malabsorption
- Drugs: methotrexate, alcohol, trimethoprim, nitrofurantoin, sulfasalazine, anticonvulsants