Macrocytic anaemia

Question 1

How common is it?

Answer 1

Pernicious anaemia accounts for 80% of cases of megaloblastic anaemia. The prevalence of vitamin B12 deficiency was abound 5% in people 65-74 years if age, and more than 10% in people 75 years of age or older.

The prevalence of folate deficiency was similar to that of vitamin B12 deficiency. Of people with low vitamin B12, only 10% had low folate levels.

Dietary vitamin B12 deficiency is unusual in younger people, except those eating strict long-term vegan diets

Question 2

What causes it?

Answer 2

Vitamin B12 deficiency. Body stores can last 2-4 years. Vit B12 combines with intrinsic factor (IF), which is produced by parietal cells in the stomach, to form an IF-B12 complex. The complex binds to surface receptors for IF in the distal ileum. Pernicious anaemia (an autoimmune disorder which results in reduced production of IF) is the most common cause of vitamin B12 deficiency in the UK.

Gastric causes (gastrectomy, gastric resection, atrophic gastritis, H.Pylori infection, or congenital intrinsic factor deficiency or abnormality. Inadequate dietary intake of B12.

Intestinal causes (malabsorption, ileal resection, Crohn’s disease affecting the ileum, chronic tropical sprue, HIV or radiotherapy to the cervix. Drugs (colchicine, neomycin, metformin, or anticonvulsants)

Question 3

How does it present?

Answer 3

Symptoms of anaemia include: fatigue and lethargy, dyspnoea, faintness, palpitations, headache, tinnitus, anorexia, angina (if the person has pre-existing coronary heart disease).

Suspect B12 deficiency if the person reports unexplained neurological symptoms (for example paraesthesia, numbness, cognitive changes, or visual disturbance).

Question 4

Investigations?

Answer 4

FBC

If the haemoglobin level is low and the MCV is high, check serum vitamin B12 and serum folate concentrations. If the haemoglobin level is low and the MCV is normal or low, check ferritin, B12, and folate levels. Conditions such as iron deficiency anaemia or thalassaemia trait can mask the development or presence of macrocystosis.

Question 5

DDx?

Answer 5

Alcohol (may cause macrocystosis with neither anaemia nor a change in liver function.

Drugs (such as hydroxycarbamide and azathioprine).

Severe thyroid deficiency (a modest increase in mean cell volume may be seen).

Pregnancy and the neonatal period. Haematological abnormalities:

Myelodysplasia – progressive bone marrow failure, with variable changes seen in the quantity and quality of red blood cells, and platelets.

Aplastic anaemia

Pure red cell aplasia.

Plasma protein changes (e.g. myeloma).

Question 6

Treatment?

Answer 6

IM B12 every 3 months following a loading dose

Folate supplementation