Friday, 19 November 2010

MRCP revision battle 54.5: Haemolysis

Haemolysis (=breakdown of red blood cells) may be intravascular or extravascular.
It causes a microcytic anaemia and raised reticulocyte count.

Intravascular haemolysis

Intravascular haemolysis is characterised by:
  • low haptoglobin (as all used up trying to 'recycle' the broken down red cells)
  • raised free plasma haemoglobin
  • haemoglobuinuria: red-brown urine
  • haemosiderinuria: once haptoglobin binding capacity is surpassed free Hb is filtered by the kidneys and can be detected in the urine in sloughed tubular cells using Prussian blue staining

Causes of intravascular haemolysis include:

Extravascular haemolysis

Extravascular haemolysis may cause splenomegaly.

Causes of extravascular haemolysis include:
  • warm AIHA (remember battle 39.7?)
  • cold haemagglutination disease
  • spherocytosis
  • haemoglobinopathies
  • haemolytic disease of the newborn

Now to the second haem battle of the day...