Macrocytosis and microcytic anaemia Flashcards
What does MCV stand for?
Mean Corpuscular (cellular) volume
What unit of measurement is used for MCV?
Femtolitres
What is the normal MCV?
80-100 fl
WHat is macrocytic MCV?
> 100fl
Name 2 causes of macrocytosis?
megaloblastic
Non-megaloblastic
What does megaloblastic mean?
An abnormally large nucleated red cell precursor with an immature nucleus
How are megaloblastic anaemias characterised?
Predominant defects in DNA synthesis and nuclear maturation with relative preservation of RNA and haemoglobin synthesis
What causes the red cell to be bigger than normal?
The nucleus is still immature
Is the larger size of a red cell due to it growing too big?
No, but its failure to become smaller
Name 4 causes of megaloblastic anaemia
B12 deficiency
Folate deficiency
Drugs
Rare inherited abnormalities
What are B12 and folate essential for?
Nuclear maturation
Enable chemical reactions that provide enough nucleosides for DNA synthesis
What does the methionine cycle produce?
s-adenosyl methionine, a methyl donor to DNA, RNA, proteins, lipids, folate intermediates.
What is folate cycle important for?
Nucleoside synthesis (i.e. uridine to thymidine conversion
What are dietary folates converted to?
Monoglutamate
absorbed in jejunum
What are the sources of B12 and folate?
B12 - animal
Folate - leafy veg, yeast destroyed by cooking
What is the body store time for B12 and folate?
B12 - 2-4 years
Folate - 4 months
Where are B12 and folate absorbed?
B12 - Ileum
Folate - Duodenum and jejunum
What is the daily requirement of B12 and folate?
B12 - 1-3ug/day
Folate - 100ug/day
What malabsorption disorders can cause folate deficiency?
Coeliac
Crohn’s
What can cause folate deficiency via excess utilisation?
Haemolysis
Exfoliating dermatitis
Pregnancy
Malignancy
What drugs can cause folate deficiency?
Anticonvulsants
What clinical features are present in both B12 deficiency and folate deficiency?
Symptoms/signs of anaemia
Weight loss, diarrhoea, infertility
Sore tongue, jaundice
Developmental problems
What are some clinical features specific to B12 deficiency and not present in folate deficiency?
Neurological problems - posterior/dorsal column abnormalities
Neuropathy, dementia, psychiatric issues
What is pernicious anaemia?
Autoimmune condition with resulting destruction of gastric parietal cells
What is pernicious anaemia associated with?
Atrophic gastritis
Personal/FHx of autoimmune disorders (e.g. addisons, hypothyroidism, vitiligo)
What autoantibodies should be checked for?
Anti gastric-parietal cell (GPC)
Anti-intrinsic factor (IF)
What is a treatment for megaloblastic anaemia?
Vit B12 injections (pernicious anaemia)
Folic acid tablets (5mg OD PO)
If life threatening - transfuse red cells
What are causes of non-megaloblastic macrocytosis?
Alcohol
Liver disease
Hypothyroidism
Marrow failure
Name 3 serious issues that are associated with anaemia?
Myelodysplasia
Myeloma
Aplastic anaemia
What is inneffective erythropoiesis?
Red cells die prematurely in the marrow.
Haem and lactate dehydrogenase are released from dead red cells
haem converted to biliruben
