Macrocytosis

Question 1

macrocytic anaemia

Answer 1

anaemia in which the red cells have a larger than normal volume

Question 2

how is size of red cells expressed

Answer 2

mean corpuscular volume (MCV)

Question 3

normal size of red cells

Answer 3

80-100fl

more than 100fl- macrocytosis

Question 4

causes of macrocytosis

Answer 4

• megaloblastic
• non-megaloblastic

Question 5

what does megaloblastic mean?

Answer 5

• larger than normal
• nucleated red cell precursor
• immature nucleus

usually based in BM

Question 6

what happens in megaloblastic anaemia?

Answer 6

• lack of red cells
• defect in DNA synthesis and nuclear maturation

-reduced division
- increased apoptosis

Question 7

causes of megaloblastic anaemia

Answer 7

• B12 deficiency
• folate deficiency
• drugs
• rare inherited abnormalities

Question 8

what is the importance of B12 and folate?

Answer 8

• DNA synthesis and nuclear formation (folate)
• DNA modification and gene activity (B12)

Question 9

cause of B12 deficiency

Answer 9

• pernicious anaemia
• chronic pancreatitis
• atrophic gastritis
• PPIs/H2 receptor antagonists
• gastrectomy and bypass
• coeliac disease
• Crohn’s disease
• Cubam receptors (inherited deficiency)
• pregnancy

Question 10

What is pernicious anaemia?

Answer 10

• autoimmune condition
• destruction of gastric parietal cells
• intrinsic factor deficiency
• B12 malabsorption and deficiency

Question 11

What is pernicious anaemia associated with?

Answer 11

• atrophic gastritis
• autoimmune disorders (hypothyroidism, vitiligo and Addison’s disease)

Question 12

where is folate absorbed?

Answer 12

jejunum

Question 13

most likely cause of folate deficiency

Answer 13

dietary cause (alcoholics)

Question 14

which drugs cause folate deficiency

Answer 14

anticonvulsants

Question 15

clinical features of B12 and folate deficiency

Answer 15

• weight loss
• diarrhoea
• infertility
• sore tongue
• jaundice
• developmental problems

more neurological problems with B12 (subacute combined degeneration of the cord)
- posterior/dorsal column abnormalities
- neuropathy
- dementia
- psychiatric manifestation

Question 16

laboratory diagnosis of B12 and folate def

Answer 16

• macrocytic anaemia (low red count)
• pancytopenia (all cells low)
• hypersegmented neutrophils and macrovalocytes (oval shape erythrocyte)

check for autoantibodies
- anti gastric parietal cells (GPC)
- anti intrinsic factor (IF)

serum levels of B12 and folate

Question 17

laboratory diagnosis of B12 and folate def

Answer 17

• macrocytic anaemia (low red count)
• pancytopenia (all cells low)
• hypersegmented neutrophils and macrovalocytes (oval shape erythrocyte)

check for autoantibodies
- anti gastric parietal cells (GPC)
- anti intrinsic factor (IF)

serum levels of B12 and folate

• Schilling’s test for B12 (not used anymore)

Question 18

Treatment for megaloblastic anaemia

Answer 18

• Vitamin B12 injections in PA
• folic acid tablets (5mg per day)

life threatening anaemia- transfuse red cells

Question 19

causes of non-megaloblastic macrocytosis

Answer 19

• alcohol
• liver disease
• hypothyroidism
• marrow failure

Question 20

what is spurious macrocytosis

Answer 20

mature red cell volume is normal
high MCV

Question 21

what can complicate megaloblastic anaemia

Answer 21

pancytopenia

Question 22

three linked pathways for RBC

Answer 22

• Embden-Myerhof pathway
• Hexose Monophosphate Shunt
• Rapapoport-Lubering shunt

Question 23

measurement of what is useful in diagnosing B12 and folate def

Answer 23

homocysteine