Macrocytosis Flashcards
macrocytic anaemia
anaemia in which the red cells have a larger than normal volume
how is size of red cells expressed
mean corpuscular volume (MCV)
normal size of red cells
80-100fl
more than 100fl- macrocytosis
causes of macrocytosis
- megaloblastic
- non-megaloblastic
what does megaloblastic mean?
- larger than normal
- nucleated red cell precursor
- immature nucleus
usually based in BM
what happens in megaloblastic anaemia?
- lack of red cells
- defect in DNA synthesis and nuclear maturation
-reduced division
- increased apoptosis
causes of megaloblastic anaemia
- B12 deficiency
- folate deficiency
- drugs
- rare inherited abnormalities
what is the importance of B12 and folate?
- DNA synthesis and nuclear formation (folate)
- DNA modification and gene activity (B12)
cause of B12 deficiency
- pernicious anaemia
- chronic pancreatitis
- atrophic gastritis
- PPIs/H2 receptor antagonists
- gastrectomy and bypass
- coeliac disease
- Crohn’s disease
- Cubam receptors (inherited deficiency)
- pregnancy
What is pernicious anaemia?
- autoimmune condition
- destruction of gastric parietal cells
- intrinsic factor deficiency
- B12 malabsorption and deficiency
What is pernicious anaemia associated with?
- atrophic gastritis
- autoimmune disorders (hypothyroidism, vitiligo and Addison’s disease)
where is folate absorbed?
jejunum
most likely cause of folate deficiency
dietary cause (alcoholics)
which drugs cause folate deficiency
anticonvulsants
clinical features of B12 and folate deficiency
- 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
laboratory diagnosis of B12 and folate def
- 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
laboratory diagnosis of B12 and folate def
- 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)
Treatment for megaloblastic anaemia
- Vitamin B12 injections in PA
- folic acid tablets (5mg per day)
life threatening anaemia- transfuse red cells
causes of non-megaloblastic macrocytosis
- alcohol
- liver disease
- hypothyroidism
- marrow failure
what is spurious macrocytosis
mature red cell volume is normal
high MCV
what can complicate megaloblastic anaemia
pancytopenia
three linked pathways for RBC
- Embden-Myerhof pathway
- Hexose Monophosphate Shunt
- Rapapoport-Lubering shunt
measurement of what is useful in diagnosing B12 and folate def
homocysteine
