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Haematology > Microcytic anaemia > Flashcards

Microcytic anaemia Flashcards

1
Q

what is anaemia

A

reduced total red cell mass

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2
Q

how is total red cell mass measured

A

Hb used as a surrogate marker (spectrophotometric method)

as it haematocrit (ratio or percentage of whole blood that is red cells)

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3
Q

what are the Hb levels that suggest anaemia

A

adult males <130

adult females <120

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4
Q

when might Hb/hct not be a good marker of anaemia

A

when patient not in a steady state- e.g. rapid blood volume loss, plasma expansion (haemodilution)

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5
Q

what is the reaction to anaemia

A

reticulocytosis (usually takes a few days- in massive haemorrhage can produce some quicker)

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6
Q

what are reticulocytes

A

red cells that have just left the bone marrow
larger than mature cells, still have RNA remnants - stain purple as a result
appear polychromatic on blood film

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7
Q

what does reticulocyte count assess

A

marrow response

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8
Q

what does blood film assess

A

cellular morphology

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9
Q

what are the two pathophysiological types of anaemia

A

decreased production- low reticulocyte count, not producing cells

increased loss or destruction of red cells- high reticulocyte count, lots of immature cells trying to replace loss

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10
Q

what can cause decreased rbc production

A

hypoproliferative- reduced amount of erythropoiesis
maturity abnormality- erythropoiesis present but ineffective: cytoplasmic defects (impaired haemoglobulinisation, nuclear defects causing impaired cell division)

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11
Q

what can cause increased loss of destruction of rbcs

A

bleeding

haemolysis (premature red cell degeneration)

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12
Q

how is anaemia classified in practise

A

using cell size and Hb content

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13
Q

what does a low MCV mean

A

microcytic

(in the context of low reticulocyte count) =cytoplasmic defect resulting in problems with haemoglobinisation

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14
Q

what does a high MCV mean

A

macrocytic

(in the context of low reticulocyte count) = nuclear defect causing impaired cell division and maturation

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15
Q

what does anaemia with a normal MCV count mean

A

hypoproliferative problem

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16
Q

where does haemoglobin synthesis occur

A

in the cytoplasm - defects in this leads to small cells= microcytic

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17
Q

what is needed to make Hb

A

globins

haem (porphyrin ring, iron (Fe2+)

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18
Q

what colour are cells with deficiency in Hb

A

hypochromic

19
Q

what type of anaemia results from inability to make Hb

A

microcytic

20
Q

what can cause hypochromic microcytic anaemias

A

deficient haemoglobin synthesis (cytoplasmic defect):
haem deficiency
-IRON DEFICIENCY
-anaemia of chronic disease (these usually normocytic)

porphyrin ring synthesis
-lead poisoning

globin deficiency
-THALASSAEMIA (problem of globin chain synthesis)

21
Q

what states can iron exist in

A

Fe2+ or Fe3+

22
Q

what is the role of iron

A

oxygen transport as Hb or myoglobin

electron transport in ATP production in mitochondria

23
Q

describe the composition of haemoglobin

A

4 globin protein subunits (2 alpha 2 beta) each contains a single haem molecule
haem molecule contains single Fe2+ ion and can bind with a single O2 molecule

24
Q

when fully saturated how much O2 will bind to 1g of Hb

A

1.34ml

25
Q

how is iron stored in the body

A

most is in haemoglobin

rest in liver and macrophage stores as the molecule ferritin (mainly in liver)

26
Q

what is circulating iron bound to

A

transferrin (this feeds it tobone marrow macrophages that then feed it to red cell precursors)

27
Q

what are the tests that assess iron status

A

function iron- Hb
transported iron- serum iron, transferring, transferring saturation
stored iron- serum ferritin

28
Q

what is transferrin

A

protein with two binding sites for iron atoms that transports iron from donor tissues (macrophages, intestinal cells, hepatocytes) to tissues expressing transferrin receptors (erythroid marrow)

29
Q

what can alter the % saturation of transferrin with iron

A

reduced in iron deficiency
reduced in anaemia of chronic disease
increased in genetic haemachromatosis

30
Q

what is ferritin

A

large intracellular protein that stores ferric ions

31
Q

why is only a small amount of ferritin present in serum

A

as intracellular

32
Q

what is serum ferritin a measure of

A

indirect measure of storage iron

low ferritin means iron deficiency

33
Q

what does low ferritin mean

A

iron deficiency

34
Q

what can cause increased ferritin

A

in the acute phase of an infection

35
Q

what confirms irons deficiency

A

anaemia (decreased functional iron)
and
reduced storage iron (low serum ferritin)

36
Q

what can cause iron deficiency

A

diet: relative deficiency (women of childbearing age), absolute deficiency (veggies/vegans)
(diet unusual to cause deficiency in men)

blood loss: usually GI, menorrhagia

malabsorption: coeliac disease, achlorhydia (e.g. people on PPIs, need acid to absorb iron)

37
Q

where in GI tract do you absorb iron

A

proximal small bowel (e.g. affected in coeliac)

38
Q

what are potential causes of chronic blood loss

A

menorrhagia
GI- tumours, ulcers, NSAIDs
haematuria

39
Q

what is the average daily intake of iron

A

1mg/day

in menorrhagia loose >30mg/ month

40
Q

what are the consquences of low iron

A

exhaust iron stores (ferritin will go down)
iron deficient erythropoiesis (falling red cell MCV)
epithelial changes: skin, koilonychia

41
Q

what is occult blood loss

A

when small volume of GI blood loss can occur without any symptoms/ signs
this can outstrip the maximum dietary iron absorption = anaemia

42
Q

is iron deficiency anaemia a diagnosis or a symptom

A

symptom- need to investigate and find underlying cause

43
Q

what is the risk or iron replacement therapy

A

relieve symptoms without treating underlying problems

Haematology (27 decks)

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