Introduction to anaemia and microcytic anaemia Flashcards
(33 cards)
What is anaemia?
Anaemia is present when there is a decrease in haemoglobin in blood below the reference level for the age and sex of the individual.
What is haematocrit?
Haematocrit measures the proportion of red blood cells in your blood.
What are the haemoglobin and haematocrit values in anaemia for adult males and females?
Adult males Hb <130g/L Hct <0.38
Adult females Hb <120g/L Hct <0.37
What is the normal response to anaemia?
To make more red cells (reticulocytosis)
Upregulation takes a few days
Reticulocytes: cells that have just left the bone marrow.
- Larger than average red cells
- Still have remnants of RNA - stain purple/deeper red, blood film appears “polychromatic”
Does decreased red cell production result in a low or high reticulocyte count and what are some causes?
Low reticulocyte count
Potential causes:
- Hypoproliferative - reduced amount of erythropoiesis
- Maturation abnormality - erythropoiesis present but ineffective
For maturation abnormality where erythropoiesis is present but ineffective, what are some of the potential causes?
Cytoplasmic defects - impaired haemoglobinisation
Nuclear defects - impaired cell division
Does increased loss or destruction of red cells result in a low or high reticulocyte count, what are some of the potential causes?
High reticulocyte count
Potential causes:
- Bleeding
- Haemolysis (rupturing/lysis of red blood cells)
What is the definition of a reticulocyte?
An immature red blood cell without a nucleus, having a granular or reticulated appearance when suitably stained.
What are the symptoms of anaemia?
The symptoms of anaemia are non - specific and include breathlessness, fatigue, headaches, palpitations and faintness.
What are the signs of anaemia?
- Pallor
- Tachycardia
- Systolic flow murmur
- Cardiac failure
Investigations for anaemia?
Bloods: full blood count
- Hb concentration, MCV, haematocrit, mean cell haemoglobin and mean cell haemoglobin concentration.
Blood film: look at cellular morphology
Reticulocyte count: assess marrow response
Additional tests - depending on clinical details and lab findings.
What is microcytic anaemia?
Anaemia caused by deficient haemoglobin synthesis (cytoplasmic defect)
What are the causes of microcytic anaemia?
Haem deficiency
Globin deficiency
What are the causes of haem deficiency in microcytic anaemia?
Lack of iron for erythropoiesis
- Iron deficiency - most common cause of microcytic anaemia
- Anaemia of chronic disease - IL-6 is released due to chronic diseases.
Problems with porphyrin synthesis
- Sideroblastic anaemia: excess iron build-up in mitochondria due to failure to incorporate iron into haem, can be hereditary (congenital sideroblastic anaemias) or acquired e.g. lead poisoning.
What are the causes of globin deficiency in microcytic anaemia?
Thalassaemia (trait, intermedia, major)
What are the causes of iron deficiency?
Insufficient intake to meet physiological need
- More likely in women and children due to greater requirements.
- Dietary factors
Losing too much - bleeding
- Causes of chronic blood loss: menorrhagia, GI (tumours, ulcers, NSAID’s, parasitic infection), haematuria.
Not absorbing enough - malabsorption e.g. coeliac disease (less common).
Summary of iron metabolic pathway?
‘Closed’ system - only able to absorb a small amount of iron
Tiny amount in circulation moving to/from storage site to being utilized – principally by marrow
Turnover in plasma pool is fast (4mg in pool and move 20mg/day)
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
Iron is stored in ferritin mainly in the liver
What is circulating iron bound to?
Transferrin
What available tests are used to assess iron status?
Functional iron
- Haemoglobin
Transported iron
- Serum iron
- Transferrin
- Transferrin saturation
Storage iron
- Serum ferritin
What is transferrin?
A protein with two binding sites for iron
Transports iron from donor tissues (macrophages, intestinal cells and hepatocytes) to tissues expressing transferrin receptors (especially erythroid marrow)
What can be used to measure iron supply?
% 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
What is ferritin?
Large intracellular protein
Spherical protein stores up to 4000 ferric ions
Tiny amount of ferritin is present in serum
- reflects intracellular ferritin synthesis in response to iron status of the host
Can serum ferritin be easily measured?
Serum ferritin is easily measured but an indirect measure of storage iron.
What does a low ferritin indicate?
Iron deficiency