Macrocytic Anaemia Flashcards
what is macrocytic anaemia?
anaemia in which the red cells have a larger than normal size
what cell can be used to estimate RBC size?
the mature lymphocytes nucleus
normocytic RBC = same size as this nucleus
what red cell precursors have a nucleus?
erythroblasts and normoblasts
reticulocytes do not
what is a true macrocytosis?
one in which there is a true increase in the volume of red cells
what are the two types of true macrocytosis?
megaloblastic
non-megaloblastic
name four causes of non-megaloblastic macrocytosis
alcohol
liver disease
hypothyroidism
marrow failure
name three causes of marrow failure that can cause non-megaloblastic macrocytosis
myelodysplasia
myeloma
aplastic anaemia
what is a spurious macrocytosis?
red cell volume is normal but MCV is measured as high
what is a megaloblast?
an abnormally large nucleated red cell precursor with an immature nucleus
what characterises a megaloblastic anaemia?
lack of red cells
maturation of megaloblasts in the marrow - presence of large precursor cells
how does a megaloblast become a macrocyte?
once appropriate Hb levels reached in the megaloblast, nucleus is extruded leaving behind a bigger than normal RBC
bevcause cell division has occurred less = less macrocytes = anaemia
what are the two main causes of megaloblastic anaemia?
B12 deficiency
folate deficiency
what is the treatment of megaloblastic anaemia in pernicious anaemia?
vitamin B12 injections for life
what is given for folate deficiency anaemia?
folic acid tablets 5mg daily
what are B12 + folate needed for?
DNA synthesis and nuclear maturation
how is B12 released from food?
by stomach acid
how is B12 protected from the stomach acid?
binds to rapid binder proteins from the saliva or stomach
what is secreted by the gastric parietal cells in response to the presence of food in the stomach?
intrinsic factor (IF)
what happens to B12 when it reaches the duodenum?
released from binder proteins and binds to IF
where is B12 bound and in what form?
the distal small bowel
bound to IF
what does B12 bind to in circulation?
transcobalamin (TC) receptors
name two sources of B12 in the diet
meat
eggs
what gastric conditions can cause B12 deficiency?
atrophic gastritis
pernicious anaemia
what medications can lead to B12 deficiency?
PPIs
H2 receptor antagonists
what small bowel conditions can result in B12 defiiency?
bacterial overgrowth
coeliac
crohn’s
what surgeries can increase risk of B12 deficiency?
gastrectomy
resection
what are dietary folates converted to for absorption?
monoglutamate
where is monoglutamate absorbed?
jejunum
name some possible causes of folate deficiency
inadequate intake
malabsorption
excess utilisation
drugs
which has higher body stores - folate or B12?
B12 (much more)
name four states that can lead to excess folate utilisation
haemolysis
exfoliating dermatitis
pregnancy
malignancy
what group of drugs can cause folate deficiency?
anti-convulsants
what foods are a source fo folate?
leafy veg
liver
fortified cereals
how long to body stores of B12 and folate last?
B12 = 2-4 years folate = 4 months
which is higher - daily requirement of folate or B12?
folate (200ug/day)
B12 is 1.5ug/day
what serious way can B12 deficiency present?
neurological problems - subacute combined degeneration of the cord
what does blood film in B12/folate deficiency anaemia show?
macrocytes
hyper-segmented neutrophils
what investigations are done for B12/folate deficiency?
measure B12 + folate
check for auto-antibodies to rule out PA
trial of therapy
in what states can low B12 not indicate B12 deficiency?
pregnancy
on the COCP
what auto-antibodies are present in pernicious anaemia (PA)?
anti gastric parietal cell (GPC)
anti IF
what is pernicious anaemia?
an autoimmune condition resulting in destruction of gastric parietal cells = IF deficiency
what are some risk factors for pernicious anaemia?
atrophic gastritis
personal or family history of other autoimmune disorders
what causes non-megaloblastic macrocytosis?
red cell membrane changes
what are two possible causes of a spurious macrocytosis?
reticulocytosis - bigger than RBCs
abnormal clumping of cells due to cold agglutinins
