Microcytic anaemia Flashcards by Alaa M.

Mnemonic for remembering the causes of microcytic anaemia

TAILS

Thalassaemia
Anaemia of chronic disease (normochromic picture)
Iron deficiency anaemia
Lead poisoning
Sideroblastic anaemia

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History of a normal haemoglobin level associated with a microcytosis

Microcytic anaemia

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A history of a normal haemoglobin level associated with a microcytosis but not at risk of thalassaemia

Polycythaemia rubra vera - iron-deficiency secondary to bleeding

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New onset microcytic anaemia in elderly patients should be..

Urgently investigated to exclude underlying malignancy

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How is Hb concentration measured?

Spectrophotometric method

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How to measure haematocrit

Automated cell counters calculate the hematocrit by multiplying the red cell number by the mean cell volume

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T or F: In rare situations, HB/hct are not a good marker of anaemia

True - rapid blood loss and haemodilution are examples of this

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What can cause decreased production of HB?

Hypoproliferative anaemia (reduced amount of erythropoiesis)

Maturation defect (erythropoiesis is active but ineffective) - Failure to produce Hb (a cytoplasmic defect) or cell division (a nulcear defect)

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What can cause decreased destruction of of HB?

Blood loss
Haemolysis

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If MCV low (microcytic) consider problems with..

Haemoglobinisation

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If MCV high (macrocytic) consider problems with..

Cell division ie maturation

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Explain the pathophysiology of microcytic anaemia..

Iron, porphyrin ring, globins are needed to make HB (if lacking then MA occurs)
Nuclear machinery is intact so cells keep dividng - for this to stop you need HB accumulation but this response is delayed
So more cell divisions occur and the cells are smaller + hypochromic

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Where is iron available?

Liver stores
Macrophages
But mostly in RBCs

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T or F: Half the volume of blood gives you the mg of iron

True

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T or F: Iron metabolism occurs in a closed system

True - only able to absorb a small amount of iron, tiny amount in circulation moving to/from storage site to being utilized (by marrow)

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Circulating iron is bound to..

Transferrin

It is transferred to the bone marrow macrophages that regulate iron uptake by transferrin receptor expression. They ‘feed’ iron to red cell precursors

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Iron turnover in the plasma pool is slow/fast

Fast (4mg in pool and move 20mg/day)

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Iron is stored in _______ mainly in the liver

Ferritin

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What are the available tests to assess iron status

Functional iron
Transported iron
Storage iron

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What is transferrin?

A protein with two binding sites for iron

What is the function of transferrin?

Transports iron from donor tissues (macrophages, intestinal cells and hepatocytes) to tissues expressing transferrin receptors (especially erythroid marrow)

% saturation of transferrin with iron is a measure of..

Iron supply

Reduced in iron deficiency
Reduced in anaemia of chronic disease
Increased in genetic haemachromatosis

Why is there only a tiny amount of ferritn in the serum?

Reflects intracellular ferritin synthesis in response to iron status of the host

T or F: Serum ferritin is easily measured but an indirect
measure of storage iron

True

Low ferritin means..

Iron deficiency

Iron deficiency can be confirmed by a combination of _______________ and _______________

Iron deficiency can be confirmed by a combination of anaemia (decreased functional iron) and reduced storage iron (low serum ferritin)

Consequences of negative iron balance

Exhaustion of iron stores (ferritin falls) Iron deficient erythropoiesis then starts (MCV falls) Anaemia develops Epithelial changes (skin, koilonychia, angular chelitis)

Causes of iron deficiency

Insufficient dietary iron Gastrointestinal, menstrual, urinary bleeding Malabsorption - absorbed in the proximal small bowel as non-haem iron needs acid environment for absorption

Give examples of malabsorption causes in iron deficiency

Coeliac disease Achlorhydria

Iron absorption can be increased by..

Iron supplements

T or F: Iron replacement therapy may relieve anaemia symptom without treating the underlying problem

True

Useful ancillary measures of iron deficiency

Improve iron intake - review diet, haem and non haem iron, improve gastric acidity Review other medication eg anticoagulants, proton pump inhibitors

T or F: Ferritin (iron stores) will not rise till after Hb returns to normal. MCV will rise as new, well haemoglobinised red cells are made

True

Rise in Hb is limited by..

Thee ability of the marrow to upregulate production of red cell Healthy marrow can increase Hb concentration by 7- 10g/l per week if well supplied with iron

Tx for iron deficiency

Oral iron replacement therapy - ferrous sulfate, gluconate and fumarate (taken 30 minutes before a meal or 2 hours before taking other medications) Can take with small amounts of food if can't tolerate GI side effects

Avoid taking oral replacement therapy with..

Milk, calcium, and antacids, high fibre foods, or caffeine

Which iron preparation is used in paediatrics?

Sodium feredetate (sytron) - liquid prep

Next step if oral iron tx was unsuccessful

Parenteral (IV) Iron

How is the dose for parenteral (IV) iron calculated?

Degree of anaemia and patient weight

Regardless of route used, when giving iron always..

Monitor response

Macrocytic anaemia (low RBC) Pancytopenia (all cells low) Blood film shows macrovalocytes and ‘hypersegmented’ neutrophils

B12/folate deficiency

When is red blood cell transfusion done?

Only if potentially life-threatening anaemia

Causes of non-megaloblastic macrocytosis (red cell membrane changes)

Alcohol, liver disease, hypothyroidism (may not be assoc. with anaemia) Marrow failure (Myelodysplasia, myeloma, aplastic anaemia - assoc. with anaemia)

What is Spurious Macrocytosis?

False macrocytosis. The volume of the mature red cell is NORMAL, but the MCV is measured as high. This can be caused by reticulocytosis or cold-agglutinins

Patients with pernicious anaemia can appear mildly jaundiced due to...

Intramedullary haemolysis

What is ineffective erythropoiesis?

Red cells die prematurely in the marrow Haemoglobin and lactate dehydrogenase (LDH) are released from dead red cells Haemoglobin converted to bilirubin

Pancytopenia can complicate..

Megaloblastic anaemia

Nuclear maturation defects can affect..

Multiple lineages