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Haematology > Macrocytosis and Macrocytic anaemia > Flashcards

Macrocytosis and Macrocytic anaemia Flashcards

1
Q

what is a macrocytic anaemia

A

anaemia where the red cells have a larger than normal volume

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2
Q

what are the units for MCV

A

femolitres

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3
Q

what will MCV be like in macrocytic anaemia

A

high

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4
Q

what will FBC be like in macrocytosis

A

MCV raised

Hb and RBC normal

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5
Q

how is MCV measured

A

light scatter properties of red cells

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6
Q

when is a red cell macrocytic

A

> 100fl

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7
Q

what are erythroblasts/ normoblasts

A

red cell precursors

have a nucleus and are usually marrow based

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8
Q

what triggers developing erythroblasts to stop dividing and loss their nucleus (enucleation)

A

when Hb accumulates to a certain level

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9
Q

what is a megoblast

A

an abnormally large nucleated red cell precursor with an immature nucleus

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10
Q

what are megablastic anaemia characterised by

A

lack of red cells due to predominant defects in DNA synthesis and nuclear maturation
(RNA and Hb synthesis are preserved)

(proerythroblasts expand but in maturing erythroblasts division is reduced and apoptosis increases)

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11
Q

what happens to cytoplasmic development and Hb accumulation in megablostic anaemias

A

normal - why the precursor cell is bigger (as has immature nucleus that isnt dividing= a megaloblast)

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12
Q

how is a macrocyte formed

A

when megaloblast (abnormally large precursor cell with immature nucleus) reaches specific level of Hb then nucleus is extruded leaving behind abnormally large red cell

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13
Q

are there more or less red cell in a macrocytic anaemia

A

less they are just bigger

less as reduced cell division and apoptosis

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14
Q

when is a cell macrocytic

A

when >100fl

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15
Q

what is a macrocyte

A

abnormally large mature red cell

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16
Q

why are cells large in megaloblatic anaemia

A

not because cell getting bigger but not able to become smaller during cell divisions

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17
Q

what does megaloblastic anaemia result in

A

larger precursor cells with immature nuclei leading to a macrocytic anaemia

18
Q

what causes megaloblastic anaemia

A

B12 deficiency
folate deficiency
drugs
rare inherited abnormalities

19
Q

why are B12 and folate important

A

essential co factors in:

  • DNA synthesis and nuclear maturation (blood cell effect)
  • DNA modification and gene activity (nerve system)
20
Q

how is B12 absorbed

A

when first consumed binds to R-binder to prevent it getting broken down with food in the stomach

in response to food being in the stomach parietal cells secrete intrinsic factor which binds to B12 and releases it from food

pancreatic secretion raise the pH in the fluid in the small intestine to further separate it

IS ABSORBED IN THE ILEUM

taken into cells bound to transcobalamin

21
Q

where is iron and calcium absorbed

A

proximal gut (duodenum- affected by crohns)

22
Q

what can cause B12 deficiency

A

diet (vegans)

stomach:
- pernicious anaemia
- atrophic gastritis
- PPIs/H2-receptor antagonists
- gastrectomy/ by-pass

pancreas:
- chronic pancreatitis

small bowel:

  • jejunum: bacterial overgrowth, coeliac disease
  • Duodenum: resection, crohns disease

cubulin receptors: inherited deficiency

23
Q

what is pernicious anaemia

A

autoimmune condition with resulting destruction of gastric parietal cells

results in intrinsic factor deficiency= B12 malabsorption and deficiency

24
Q

what is pernicious anaemia associated with

A

atrophic gastritis

personal/ FHx of other autoimmune disorders (hypothyroidism, vitiligo, addisons)

25
Q

how is folate absorbed

A

dietary folates converted to monoglutamate

absorbed in the jejunum and duodenum (diffusion and actively)

26
Q

what are sources of B12

A

animal produce

27
Q

what is the requirement for B12

A

1.5 micrograms a day

stores last 2-4 years

28
Q

what is the requirement for folate

A

200 micrograms a day

body stores last 4 months

29
Q

what causes folate deficiency

A

inadequate intake: diet (esp in alcoholics)

malabsorption: coeliac disease, crohns

excess utilisation (using folate to make DNA very quickly): haemolysis, exfoliating dermatitis, pregnancy, malignancy

drugs: anticonvulsants (enhance folic acid metabolism)

30
Q

what are the features of B12 and folate deficiency

A

symptoms/ signs of anaemia
weight loss, diarrhoea, infertility
sore tongue, jaundice
development (motor delay) problems

for B12 especially: neurological problems- dorsal column abnormalities, neuropathy, dementia, psych manifestations (these can be irreversible)

31
Q

how is megalobastic anaemia diagnosed

A

red cell count is low
(pancytopenia in some patients)
blood film shows macrovalocytes and hypersegmented neutrophils (3-5 nuclear segments)

assay B12 and folate levels in serum
check for auto-antibodies:
-anti-intrinsic factor IF
-anti gastric parietal GPC

32
Q

what are the types of causes of macrocytosis

A 
megaloblastic (B12 or folate deficiency) 
non megaloblastic (alcohol, liver disease, hypothyroidism, marrow failure)

spurious (false)

33
Q

what is the treatment for megaloblastic anaemia

A

treat the cause where possible
B12 injections for life if pernicious anaemia
folic acid 5mg tablets per day

if potentially life threatening transfuse red cells

34
Q

what can cause non megaloblastic macrocytosis

A

alcohol, liver disease, hypothyrioidism (these may not be associated with anaemia)

marrow failure: myelodysplasia, myeloma, aplastic anaemia (these all associated with anaemia)

35
Q

what is spurious macrocytosis

A

when the volume of the red cell is normal but the MCV is recorded as high: false diagnosis

36
Q

what can cause spurious macrocytosis

A

reticulocytosis

cold agglutinins

37
Q

what is reticulocytosis

A

an increase in reticulocyte numbers (bigger than mature cells) occurs a marrow response to acute blood loss/ red cell breakdown (haemolysis)

38
Q

what should you think in a macrocytic anaemia with raised reticulocyte count

A

haemorrhage/ haemolysis causing reticulocytosis

39
Q

what other symptoms might people with pernicious anaemia have

A

mild jaundice due to intramedullary haemolysis (released but not mature) and pallor due to anaemia

40
Q

what is released from dead red blood cells

A

lactate dehydrogenase and Hb

41
Q

what can complicate severe megaloblastic anaemia

A

pancytopenia

Haematology (27 decks)

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