Macrocytosis

Question 1

what is macrocytic anaemia

Answer 1

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

Question 2

units of MCV

Answer 2

femtolitrie (1 is = to 10-15L)

Question 3

macrocytic anaemia levels

Answer 3

low Hb
low RBC
increased MCV

Question 4

macrocytosis levels

Answer 4

normal Hb
normal RBC
increased MCV

Question 5

normal MCV

macrocytic MCV

Answer 5

80-100fl

>100fl

Question 6

true causes of macrocytosis

Answer 6

megaloblastic

non megaloblastic

Question 7

what does megaloblastic mean

Answer 7

an abnormally large nucleated red cell precursor with an immature nucleus

Question 8

what does a mature red cell look like

Answer 8

membrane surrounding soluble proteins and electrolytes

Question 9

what do precursors of red cells until the reticulocyte have

Answer 9

nucleus (erythroblasts) and are marrow based

Question 10

developing erythroid cells in marrow - what happens

Answer 10

accumulate hb
reduce in size
stop dividing and lose nucleus - regulated by hb content

Question 11

when does hb start increasing

Answer 11

from basophilic to reticulocyte

Question 12

when does enucleation happen

Answer 12

between orthochromatic and reticulocyte

Question 13

how are megaloblastic anaemias characterised

Answer 13

by predominant defects in DNA synthesis and nuclear maturation with relative preservation of RNA and haemoglobin synthesis

Question 14

cellular consequence of mesoblastic anaemia

Answer 14

cytoplasm develops and becomes mature and big enough to divide, the nucleus is still immature
this leads to a bigger than normal red cell precursor

Question 15

the larger cell size in megaloblastic anaemia is not due to what and is due to what

Answer 15

not due to increase in size of developing cell but a failure to become smaller

Question 16

cause of megaloblastic anaemia

Answer 16

B12 deficiency
folate deficiency
others - drugs, rare inherited abnormalities

Question 17

why does lack of b12 or folate cause megaloblastic anaemia

Answer 17

b12 and folate are essential cofactors for nuclear maturation
they enable chemical reactions that provide enough nucleosides for DNA synthesis

Question 18

folate absorption - what is dietary folate converted to

where is it absorbed

Answer 18

converted to monoglutamate

absorbed in jejunum and d

Question 19

source of b12 and folate

Answer 19

b12 - animal

folate - leafy veg, yeast. destroyed by cooking

Question 20

bode stores for folate and b12

Answer 20

b12 2-4 ears

folate 4 m

Question 21

absorbed where b12 folate

Answer 21

b ileum

f duodenum and jej

Question 22

daily requirement of b12 and folate

Answer 22

b 1-2 ug/day

folate 100ug/day

Question 23

causes of folate defic

Answer 23

inadequate intake
malabsorption - coeliac, crohns
excess utilisation - haemolytic, exfoliating dermatitis, preg, malig
drugs - anticonvulsants

Question 24

clinical features of b12 and folate defic

Answer 24

symp and signs of anaemia
weight loss, diarrhoea, infertility
sore tongue, jaundice
developmental problems

Question 25

vitamin b12 defic only - myelin sheath

Answer 25

neurological problems - post/dorsal column abnormalities, neuropathy, dementia, psychiatric manifestations

Question 26

what is pernicious anaemia

Answer 26

autoimmune condition with resulting destruction of gastric parietal cells

Question 27

what is pernicious anaemia associated with

Answer 27

atrophic gastritis and personal or family history of other autoimmune disorders - hypothyroidism, vitiligo, addisons

Question 28

lab dx of pernicious anaemia

Answer 28

macrocytic anaemia - red cells low

pancytopenia - all cells low in some px

blood film shows macrovalocytes and hyperhsegmented neutrophils (normally 3-5 nuclear segments)

assay b12 and folate levels in serum - low levels don’t mean defic and normal levels don’t mean normal

autoantibodies anti gastric-parietal GPC and anti intrinsic factor IF
schillings test

bone marrow exam - not usually required

Question 29

anti GPC

anti IF

Answer 29

sensitive and not specific

more specific, not sensitive

Question 30

treatment of megaloblastic anaemia

Answer 30

treat the underlying cause
vit b12 injections for life in pernicious anaemia
folic acid tablets 5mg/day PO
if life treating anaemia - transfuse red cells

Question 31

causes of non megaloblastic macrocytosis

Answer 31

alcohol
liver disease
hypothyroidism
—may not be assoc w anaemia, due to red cell membrane changes

marrow failure - myelodysplasia, myeloma, aplastic anaemia
—assoc w anaemia

Question 32

spurious macrocytosis

Answer 32

the size of the mature red cell is normal but the MCV is measured as high

Question 33

cause of spurious

Answer 33

when there is an increase in reticulocyte numbers as a marrow response to acute blood loss or red cell breakdown (haemolysis)

reticulocytes are bigger than mature red cells and are analysed along with these for the MCV measurements

Question 34

why can patients with percinioous anaemia appear mildly jaundiced

Answer 34

due to intramedullary haemolysis

Question 35

ineffective erythropoiesis

Answer 35

red cells die prematurely in the marrow
hb and lactate dehydrogenase are released from dead red cells
hb converted to bilirubin

Question 36

what can complicate severe megaloblastic anaemia

Answer 36

pancytopenia

Question 37

what defects can affect multiple lineages

Answer 37

nuclear maturation