Anaemia and microcytic anaemia Flashcards
Definition of anaemia
Reduced total red cell mass
- red cell concentration is only a surrogate marker
When would Hb concentration and haematocrit not be useful/reliable markers?
In cases of acute bleeding, the body haven’t got a chance to replenish blood volume with extracellular fluid (plasma expansion), so despite huge volume of blood loss, percentage of red cell is not dropped
What does reticulocytosis mean?
increased number of reticulocytes, indicating an active attempt of bone marrow’s increased red cell production
Usually seen in haemolytic anaemia or hemorrhage
Describe characteristics of reticulocytes.
Red cells that have just left the bone marrow
Larger than average red cells
Still have remnants of protein making machinery (RNA) –> hence stain purple/deeper red
Blood film appears ‘polychromatic’
There may be an initial ‘burst’ of marrow reticulocytes in acute haemorrhage but up-regulation of reticulocyte production by the bone marrow in response to anaemia takes a few days
How to classify anaemia pathophysiologically?
How is mean cell volume (MCV) a useful tool in distinguishing cytoplasmic and nuclear defects?
If MCV low (microcytic) consider problems with haemoglobinisation –> a cytoplasmic issue
If MCV high (macrocytic) consider problems with cell division –> a nuclear issue
What is the pathophysiology of hypochromic microcytic anaemias?
Hb is synthesised in the cytoplasm
To make Hb you need all the building blocks: available iron, porphyrin ring and globins - if one of these is lacking the result is a microcytic anaemia
Since the nuclear machinery is intact cells can keep dividing. One of the signals to stop dividing is Hb accumulation, as this is delayed, more cell divisions occur and the cells are smaller (microcytic)
Because they contain little Hb they are hypochromic (lacking in colour)
What are causes of hypochromic microcytic anaemias?
IRON DEFICIENCY is major cause
Basically you either lack haem or lack globins
Haem deficiency:
- Iron deficiency (low body iron)
- some cases of anaemia of Chronic Disease (normal body iron but lack of available iron) – but most anaemia of chronic disease is normocytic
- problems with porphyrin synthesis (rare)
- Thalassaemia (globin deficiency)
Describe iron metabolism
Functional iron (in Hb), serum iron (transferrin) and storage iron (ferritin)
What are some tests for iron and what do the results imply?
- % saturation of transferrin with iron
reduced in iron deficiency, anaemia of chronic disease
increased in genetic haemachromatosis - Serum ferritin
Most ferritin proteins are intracellular, a tiny amount is present in serum - reflects intracellular ferritin synthesis in response to iron status of the host - hence is an indirect measure of storage iron
reduced in iron deficiency
How is iron deficiency confirmed and what are the sequential consequences?
It can be confirmed by a combination of anaemia (low functional iron) and low serum ferritin (low storage iron)
- Exhaustion of iron stores (ferritin falls)
- Iron deficient erythropoiesis then starts (MCV starts to fall)
- Anaemia then develops
- Epithelial changes (late effects in other sites of the chronic lack of iron)
- skin
- koilonychia
- angular chelitis
What are causes of iron deficiency?
- Insufficient dietary iron
- Losing iron (usually chronic blood loss)
- GI tumours/ulcers/NSAIDs
- Menorrhagia
- Haematuria - Malabsorption of iron (rather uncommon for presenting
- non-haem iron needs acid environment for absorption
- coeliac disease
- achlorhydria
What is the maximum dietary iron absorption?
about 1mg per day even if you consume heavily, which can be very little if there is a cause of chronic blood loss
Iron-deficiency anaemia is a symptom not diagnosis
Supplementing or replacing iron is only symptom-relieving, need to investigate and treat underlying cause(s)
What are some things to have in mind when treating iron-deficiency anaemia?
