Haemolysis

Question 1

What is haemolysis?

Answer 1

Premature red cell destruction

Question 2

Why are red cells so susceptible to damage?

Answer 2

Need to have a biconcave shape

Rely on glycolysis - no mitochondria

Can’t replicate or repair damage - no nucleus

Question 3

What is compensated and decompensated haemolysis?

Answer 3

Increased red cell destruction compensated by increased red cell production

Decompensated haemolysis is when there is increased red cell destruction which exceeds bone marrow capacity for production

Question 4

What are some of the possible consequences of haemolysis?

Answer 4

Reticulocytosis

Erythroid hyperplasia

Excess red cell breakdown products e.g bilirubin

Question 5

What are some of the possible causes of intravascular haemolysis?

Answer 5

Abnormal blood products are spilled directly into the circulation

ABO incompatible blood transfusion

G6PD deficiency

Severe falciparum malaria (blackwater fever)

PNH and PCH

Question 6

What are some of the clinical features of intravascular haemolysis?

Answer 6

Haemoglobinaemia (Free Hb in the circulation)

Methaemalbuminaemia (Hb bound to albumin)

Haemoglobinuria (pink urine - turns black when left to stand)

Haemosiderinuria (brown urine)

Question 7

What is the problem in extravascular haemolysis?

Answer 7

Normal products are in excess

Question 8

Where does extravascular haemolysis mostly affect?

Answer 8

The reticuloendothelial system

liver and spleen

Question 9

How does extravascular haemolysis present?

Answer 9

Hyperplasia at the site of destruction (hepatomegaly and splenomegaly)

Jaundice and gall stones (unconjugated bilirubinaemia)

Question 10

Autoimmune causes of haemolysis can be split into warm or cold autoantibody. Which antibodies are involved and which is most common

Answer 10

Warm = IgG - most common

Cold = IgM

Question 11

What is the difference between autoimmune and alloimmune haemolysis?

Answer 11

Autoimmune haemolysis = own antibodies

Alloimmune haemolysis = passive transfer of antibodies

Question 12

What are some of the possible causes of alloimmune haemolysis?

Answer 12

Haemolytic transfusion reaction

Haemolytic disease of the newborn

ABO incompatibility

Question 13

What are some of the mechanical causes of haemolysis?

Answer 13

Disseminated intravascular coagulation

Haemolytic uraemic syndrome

Leaking heart valve

Infections

Burns

Question 14

What are some of the causes of abnormal cell membrane which can cause haemolysis?

Answer 14

Hereditary spherocytosis

Liver disease

Vitamin E deficiency

Paroxysmal nocturnal haemoglobinuria

Question 15

Name a cause of abnormal red cell metabolism which can lead to haemolysis

Answer 15

G6PD deficiency

Question 16

Name a cause of abnormal haemoglobin which can cause haemolysis

Answer 16

Sickle cell disease (HbS)

Question 17

What investigations can be done for haemolysis?

Answer 17

FBCs 
Blood film 
Reticulocyte count 
Serum unconjugated bilirubin 
Serum haptoglobin 
Urinary urobilinogen 
Coomb's test

Question 18

What is the function of Coomb’s test?

Answer 18

Identifies antibodies and complements bound to own red cells

A positive test involves agglutination