Red cell precursors

• Myeloblasts
• Myelocytes
• Early normoblasts
• Late normoblasts
• Reticulocytes 

Anaemia

Megaloblastic Anaemia

• Megaloblast = abnormal nucleated cell not usually found in the body, present in BM and occasionally found in peripheral blood

1. B12
   • Functions as co-enzyme to produce methionine from tetrahydrofolate 
   • 3 years store
   • Deficiency in (1) Pernicious anaemia GPC antibodies (2) partial/total gastrectomy (3) failure to absorp from terminal ileum
2. Folate
   • Tetrahydrofolate used to form methionine from homocysteine
   • 3 months store in liver
   • Deficiency (1) inadequate intake or excess demand in pregnancy (2) vegans (3) drugs which have an anti-folate action 

Haemolytic anaemia

1. Congenital
   • Membrane abnormalities: spherocytosis (spectrin), elliptocytosis, abetalipoproteinaemia
   • Abnormal Haemoglobinopathies: SCC, HbC, HbD, thalassaemia
   • Enzyme deficiency: G6PD, pyurvate kinase, glutathione synthetase deficiency
2. Acquired
   • Immune
   • Mechanical - artificial heart valves, microangiopathic haemolytic anaemia

Diagnosis:

• low Hb, normochromic normocytic - macrocytic (raised Red cell distribution width)
• Raised reticulocyte count
• Excess unconjugated bilirubin

Haematocrit

Proportion of total blood volume that consists of red cells
Expressed as percentage / fraction
Normally = 0.4 - 0.45

Determines oxygen-carrying capacity of blood
Determines blood viscosity

Determinants

1. Red cell volume
   • Blood loss
2. Plasma volume
   • Loss of water
   • Plasma expansion - pregnancy