Microcytic anaemia Flashcards
What is anaemia
reduced red blood cell mass
How is red blood cell mass measured?
Haemoglobin concentration is surrogate (indicator) of red blood cell mass
Haematocrit
What is haematocrit
percentage of total blood volume that consists of red cells
In what scenarios are haemoglobin concentration and haematocrit poor marker of anaemia?
rapid blood volume loss (bleeding) - Hb and Hct will be same
plasma expansion (IV fluids) - Hct will be decreased but Hb will be the same
How is Hb concentration measured?
red cells are burst to form haemoglobin solution
haemoglobin is stabilised and then the optical density is measured
What are reticulocytes
immature red cells that have just been formed in the bone marrow
describe reticulocytes
large, stain purple or deep red
contain RNA
polychromasia of blood film results from RNA in reticulocytes
reticulocytosis occurs in response to anaemia
What is MCV
mean cell volume (volume of red cell)
What are the causes of anaemia
decreased production
increased loss or destruction
How is decreased production identified
low reticulocyte count
What causes decreased production of red cells
hypoproliferative (reduced erythropoiesis)
maturation abnormality (erythropoiesis ineffective)
- impaired haemoglobinisation
- impaired cell division
What are some causes of increased loss or destruction of red cells
haemolysis
bleed / haemorrhage
How is increased loss or destruction identified
High reticulocyte count
What is the difference between microcytic and macrocytic anaemia
microcytic - low MCV (consider problem with haemoglobinisation
macrocytic - high MCV (consider problem with maturation)
Where does haemoglobin synthesis occur?
cytoplasm
What is required for haemoglobin synthesis
Haem and globin
What does haem group consist of?
haem group is porphyrin ring containing Fe2+ and protoporphyrin
What effect does defect in cytoplasmic synthesis of haemoglobin have on cell size?
results in small cells with low Hb content
cells are microcytic (small) and hypochromatic
What is the microcytic, hypochromatic anaemia due to
deficient haemoglobin synthesis - a cytoplasmic defect
What are some causes of deficient haemoglobin synthesis and thus microcytic, hypochromatic anaemia
Iron defficiency (from dietry intake) chronic disease (normal body iron but lack of available iron)
Problem with porphyrin synthesis - lead poisoning (very rare)
Globin defficiency - thalassaemia
Mostly due to iron defficiency or thalassaemia
in what two states can iron exist and what is it used for in the body
Fe2+ Fe3+
used to transport oxygen and also in mitochondrial production of ATP
why is iron toxic
creates free radicals
Where is most iron stored in the body?
in haemoglobin (2500mg)
where else is iron stored in the body?
in liver (500mg) and in macrophages (500mg)
What molecule is iron stored in? and how many molecules of iron can it store?
Ferritin can store 4000 molecules of iron
What molecule is iron transported in?
Transferrin
What do you measure to measure Iron stores in the body
Ferritin count
low ferritin means iron deficiency
What will you see in iron deficiency anaemia
microcytic, hypochromatic anaemia
low serum ferritin
What does transferring do?
transports iron from donors (macrophages in bone marrow, hepatocytes etc) to tissues expressing transferrin receptors
What are some causes of iron deficiency
not eating enough in diet
losing too much (bleeding - usually GI)
not absorbing enough (coeliac)
what are some consequences of negative iron balance
exhaustion of iron stores
iron deficient erythropoiesis (decreased in MCV)
microcytic hypochromatic anaemia
skin changes, koilonychia
