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Haematology SB > Iron > Flashcards

Iron Flashcards

1
Q

what is iron essential for

A 
oxygen transport 
electron transport (e.g. mitochondrial production of ATP)

present in = haemoglobin, myoglobin, enzymes

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2
Q

what can chemical reactivity cause in iron

A

oxidative stress

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3
Q

why is it difficulty to get rid of iron in the body

A

there is no mechanism for excretion

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4
Q

where does iron sit on Hb

A

prophyrin ring

- where most body iron resides

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5
Q

where does the body have most of its iron

A 
Hb - 2500mg
Macrophage stores - 500mg
Liver stores - 500mg 
Erythroid marrow - 150mg
Plasma - 4mg
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6
Q

what is the only way to influence iron levels

A

through absorption

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7
Q

how can assess iron status

A

Functional iron:
- haemoglobin concentration

Transport iron/iron supply to tissues:
- % saturation of transferrin with iron

Storage iron:

  • serum ferritin
  • tissue biopsy (bone marrow for Fe deficiency; liver for iron overload)‏
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8
Q

what is the role of transferrin

A

Transports iron from donor tissues (macrophages, intestinal cells where iron is being absorbed and hepatocytes) to tissues expressing transferrin receptors i.e. tissues that need it

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9
Q

how does transferrin work

A

binds to iron in the Fe3+ state and takes it to where it is needed

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10
Q

what does transferrin saturation measure

A

iron supply

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11
Q

what is holo- and app-transferrin

A

holotransferrin = iron bound to transferrin

apotransferrin = unbound transferrin

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12
Q

what is ferritin

A

large protein, that stores iron in Fe3+ form

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13
Q

what does serum ferritin levels show

A

indirect measure of storage iron

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14
Q

why does an increased ferritin level not necessarily have anything to do with iron

A

acts as an acute phase protein

also goes up with infection, malignancy etc

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15
Q

when would serum ferritin levels be low

A

iron deficiency

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16
Q

how is iron absorption regulated

A

Ferroportin

Hepcidin

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17
Q

what is Hepcidin

A

The major negative regulator of iron uptake

Produced in liver in response to iron load and inflammation

Down-regulates ferroportin

18
Q

where is iron absorbed

A

duodenum

19
Q

through what mechanism is iron absorbed

A

DMT-1
- transports iron into the duodenal enterocyte

Ferroportin

  • Facilitates iron export from the enterocyte
  • Passed on to transferrin for transport elsewhere
20
Q

what are consequences of negative iron balance

A 
1 - Exhaustion of iron stores
2 - Iron deficient erythropoiesis
= Falling red cell MCV
3 - Microcytic Anaemia
4 - Epithelial changes: 
     > skin
     > Koilonychia
     > Angular stomatitis
21
Q

what are causes of a hypochromic microcytic anaemia

A

haem deficiency

  • lack of iron
  • congential sideroblastic anaemia

globin deficiency
- thalassaemia

22
Q

what are causes of a lack of iron

A

iron deficiency

anaemia of chronic disease

23
Q

how could you tell apart hypochromic microcytic anaemia caused by iron deficiency or anaemia of chronic disease

A

iron deficiency
= low body iron

anaemia of chronic disease
= normal body iron

24
Q

what test results are indicative of iron deficiency

A

anaemia (decreased haemoglobin iron)

reduced storage iron (low serum ferritin)


25
Q

what are causes of iron deficiency

A

Insufficient dietary intake

  • particularly women and children
  • vegetarian diets

Losing too much - bleeding (from any source i.e. GI bleeding)

Not absorbing enough – malabsorption

26
Q

what are causes of chronic blood loss

A

Menorrhagia

Gastrointestinal
- Tumours, Ulcers, NSAIDs, Parasitic infection

Haematuria

27
Q

what is important to remember about iron deficiency anaemia

A

it is a symptom not a diagnosis

requires investigation for an underling cause

28
Q

what does anaemia of chronic disease interfere with

A

red cell breakdown in the macrophage

29
Q

what happens in anaemia of chronic disease

A
  1. Increased transcription of Ferritin mRNA stimulated by inflammatory cytokines so ferritin synthesis increased
  2. Increased plasma Hepcidin blocks ferroportin-mediated release of iron
  3. Results in impaired iron supply to marrow erythroblasts and eventually hypochromic red cells
30
Q

what is primary iron overload

A

Long-term excess iron absorption with parenchymal rather than macrophage iron loading, and eventual organ damage

31
Q

what are clinical features of hereditary haemochromatosis

A 
Weakness/fatigue
Joint pains
Impotence
Arthritits
Cirrhosis
Diabetes
Cardiomyopathy
Bronze skin
32
Q

how does hereditary haemochromatosis present

A

Presentation usually in middle age or later

Iron overload > 5g

33
Q

what is affected in haemochromatosis

A

Mutations of HFE gene on chromosome 6

  • Main effect likely to be via reduced hepcidin synthesis
  • causes iron accumulation
  • autosomal recessive
34
Q

what blood results are seen in haemochromatosis

A

increased LFT

increased serum ferritin

transferrin saturation >50%

35
Q

what other diagnostic test can be done in haemochromatosis

A

liver biopsy

36
Q

Tx for hereditary haemochromatosis

A

Weekly phlebotomy

Initial aim to exhaust iron stores (ferritin <20 µg/l)‏

Thereafter keep ferritin below 50 µg/l

Insulin

37
Q

what is secondary haemochromatosis also known as

A

iron-loading anaemias

38
Q

what causes iron-loading anaemia

A

Repeated red cell transfusions

Excessive iron absorption related to over-active erythropoiesis

39
Q

what conditions and their treatment may lead to iron-loading anaemia

A

Thalassaemia syndromes
Sideroblastic anaemias
Red cell aplasia
Myelodysplasia (MDS)

40
Q

what is treatment of secondary iron overload

A

Treatment by venesection not an option in already anaemic patients

Iron chelating agents:
Desferrioxamine (s.c. or IV infusion)‏

Haematology SB (19 decks)

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