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haematology > Macrocytic anaemia > Flashcards

Macrocytic anaemia Flashcards

1
Q

What is macrocytosis

A

increase in number of big cells

usually refers to RBC’s

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2
Q

What is macrocytic anaemia

A

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

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3
Q

How is size of the cell expressed or detected

A

MCV (mean cell volume)

units are femtolitres

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4
Q

give size (in fl) of normal and macrocytic red blood cells

A

normal = 80-100 fl

macrocytic = >100 fl

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5
Q

What are the types of macrocytic anaemia

A

True: megalobastic and non-megaloblastic

false (spurious) =

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6
Q

What is a megaloblast?

A

erythroblast = normal red cell precursor with nucleus

megaloblast = abnormally large nucleated red cell precursor

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7
Q

what is megaloblastic anaemia?

A

defect in DNA synthesis and nuclear maturation with sparing of RNA and haemoglobin synthesis

cytoplasm = normal 
nucleus = lags, immature
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8
Q

What is the cellular consequence of this defect in DNA and nuclear maturation?

A

cytoplasm develops normally and is large enough to divide but the nucleus isnt and lags behind. This results in an abnormally large cell

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9
Q

What are some causes of megaloblastic anaemia?

A

B12 deficiency
folate deficiency
other: drug, inherited

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10
Q

Why are B12 and folate deficiency causes of megaloblastic anaemia?

A

B12 and folate are essential for nuclear maturation as they provide chemical reactions that provide nucleosides for DNA synthesis and replication

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11
Q

what is required to absorb B12 in the gut?

A

intrinsic factor is required

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12
Q

what cells secrete intrinsic factor?

A

parietal cells in the stomach

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13
Q

Where in the small bowel is B12 absorbed into the blood stream??

A

terminal ileum

patients with terminal ileum resection will malabsorb B12

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14
Q

What are some causes of B12 deficiency?

A 
inadequate intake in diet (vegans)
absorption defect (pernicious anaemia, gastrectomy, tape worm)
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15
Q

What are dietry folates converted to?

A

monoglutamate

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16
Q

where are folates absorbed in the small bowel?

A

duodenum and jejunum

17
Q

What foods provide B12 and folate?

A

B12 - meat

folate - leafy veg, yeast (destroyed by cooking)

18
Q

What are some causes of folate deficiency?

A

inadequate dietary intake

inadequate absorption (coeliac, crohns)

excess utilisation - haemolysis, pregnancy, malignancy, dermatitis

drugs - anticonvulsants

19
Q

What are symptoms and signs of B12 and folate deficiency?

A

signs and symptoms of anaemia

weight loss, diarrhoea, sore tongue, jaundice

20
Q

What can happen with B12 deficiency?

A

neurological signs as B12 affects myelin sheath

dorsal column signs, dementia, neuropathy

21
Q

What is pernicious anaemia?

A

autoimmune destruction of gastric parietal cells

no secretion of IF so no absorption of B12

22
Q

What is pernicious anaemia associated with?

A

atrophic gastritis and other autoimmune conditions like addisons, vitiligo, hypothyroidism

23
Q

What cell mediates the autoimmunity of pernicious anaemia

A

CD4

24
Q

How do you diagnose pernicious anaemia in laboratory?

A

macrocytic anaemia

pancytopaenia (reduction in number of all cells)

hypersegmented neutrophils
macrovalocytes (enlarged oval shaped erythrocyte)

25
Q

How else can you diagnose pernicious anaemia in the lab?

A

assay B12 and folate levels

check for autoantibodies: anti gastric-parietal cell (anti-GPC)
anti intrinsic factor (anti-IF)

schillings test

26
Q

How do you treat megaloblastic anaemia

A

treat cause

give B12 injection

folic acid tablets

transfuse red cells if life threatening

27
Q

What are some causes of non-megaloblastic macrocytosis

A

alcohol
liver disease
hypothyroidism
(these may not be associated with anaemia and are due to red cell membrane changes)

marrow failure

  • myeloma
  • myelodysplasia
  • aplastic anaemia
28
Q

what are some types of spurious (false) macrocytosis

A

reticulocytosis

cold agglutinins

29
Q

what is reticulocytosis

A

formation of reticulocytes in response to decreased erythrocytes (haemolysis / bleed)

30
Q

Why is reticulocytosis confused with macrocytosis

A

reticulocytes are the precursor to RBC’s and are larger than mature red blood cells

31
Q

How is cold agglutinins confused with macrocytosis

A

red blood cells clump together and appear to be one abnormally large red cell

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