Haemolysis Flashcards
What is haemolysis?
Premature red cell destruction
Why are red cells particularly susceptible to damage?
- they need to have a biconcave shape to transit the circulation successfully
- They have limited metabolic reserve and rely exclusively on glucose metabolism for energy (no mitochondria)
- They cannot generate new proteins once they are in the circulation (no nuclei).
What is compensated haemolysis? What happens to the Hb?
Increased red cell destruction compensated by increased red cell production.
The Hb is maintained.
What is decompensated haemolysis? What happens to the Hb?
Another name for haemolytic anaemia.
Increased rate of red cell destruction exceeding bone marrow capacity for red cell production.
The Hb falls.
What are the consequences of haemolysis?
Reticulocytosis
Erythroid hyperplasia
Increased red cell breakdown products
Is reticulocytosis diagnostic of haemolysis?
No - it occurs in other conditions e.g. blood loss, response to iron therapy for iron deficiency anaemia.
Where are red cells predominantly broken down in extravascular haemolysis?
The liver and the spleen
What may be a physical sign of extravascular haemolysis?
Hyperplasia at the site of red cell destruction (e.g. splenomegaly +/- hepatomegaly)
What breakdown products of extravascular haemolysis can be measured?
What complications might they cause when released in excess?
Unconjugated bilirubin –> gallstones, jaundice
Urobilinogen in the urine
What products of intravascular haemolysis might be detected?
Haemoglobin (haemoglobinaemia)
Methhaemalbuminaemia
Haemoglobinuria (pink urine, turns black on standing)
Haemosidinuria
Name 5 causes of intravascular haemolysis
ABO incompatible blood transfusion G6PD deficiency Falciparum malaria (blackwater fever) Paroxysmal nocturnal haemoglobinuria Paroxysmal cold haemoglobinuria
What investigations can be done to confirm haemolysis?
FBC Blood film Reticulocyte count Serum haptoglobins Serum unconjugated bilirubin Urinary urobilinogen
What are the signs on bloodfilm of a) membrane damage b) mechanical damage c) oxidative damage?
a) spherocytes
b) red cell fragments/schiscocytes
c) Heinz bodies
What are the types of haemolysis as classified by the site of the red cell defect?
Premature destruction of normal red cells
Abnormal cell membrane
Abnormal cell metabolism
Abnormal haemoglobin
Name different causes of warm and cold autoimmune haemolysis
What type of antibodies mediate both these disorders?
Warm (IgG): Idiopathic Autoimmune disorders Lymphoproliferative disorders Drugs (penicillins, methyldopa and quinine) Infections Cold (IgM): Idiopathic Infections (EBV, mycoplasma) Lymphoproliferative disorders
What is the treatment of autoimmune haemolytic disorders?
Steroids to induce remission
Immunosuppressants if relapse
Can do splenectomy if no response to steroids, but not for the cold ones (IgM) because most RBCs are destroyed in the liver
Name the causes of alloimmune haemolysis
Immune response (antibody produced): immediate (IgM) or delayed (IgG) haemolytic transfusion reaction Passive transfer of antibodies: haemolytic disease of the newborn
Name five causes of mechanical haemolysis
Disseminated intravascular coagulation Haemolytic uraemic syndrome Thrombotic Thrombocytopenic Purpura Leaking heart valve Infections e.g. malaria
What is a sign of mechanical haemolysis on blood film?
Schistocytes
What is seen on blood film of burns related haemolysis? Why does this occur?
Microspherocytes
Red cells are sheared as they pass through damaged capillaries in severe burns
Name three acquired causes of abnormal red cell membrane
Liver disease (Zieve's syndrome) Vitamin E deficiency Paroxysmal nocturnal haemoglobinuria
What is Zieve’s syndrome?
What is seen on blood film?
Characterised by haemolysis, alcoholic liver disease and hyperlipidaemia.
Blood film: anaemia, polychromatic macrocytes, irregularly contracted cells
What is a congenital cause of an abnormal red cell membrane that can cause haemolysis?
Hereditary spherocytosis
