Haemolysis

Question 1

What is haemolysis?

Answer 1

Premature red cell destruction

Question 2

Why are red cells particularly susceptible to damage?

Answer 2

1. they need to have a biconcave shape to transit the circulation successfully
2. They have limited metabolic reserve and rely exclusively on glucose metabolism for energy (no mitochondria)
3. They cannot generate new proteins once they are in the circulation (no nuclei).

Question 3

What is compensated haemolysis? What happens to the Hb?

Answer 3

Increased red cell destruction compensated by increased red cell production.
The Hb is maintained.

Question 4

What is decompensated haemolysis? What happens to the Hb?

Answer 4

Another name for haemolytic anaemia.
Increased rate of red cell destruction exceeding bone marrow capacity for red cell production.
The Hb falls.

Question 5

What are the consequences of haemolysis?

Answer 5

Reticulocytosis
Erythroid hyperplasia
Increased red cell breakdown products

Question 6

Is reticulocytosis diagnostic of haemolysis?

Answer 6

No - it occurs in other conditions e.g. blood loss, response to iron therapy for iron deficiency anaemia.

Question 7

Where are red cells predominantly broken down in extravascular haemolysis?

Answer 7

The liver and the spleen

Question 8

What may be a physical sign of extravascular haemolysis?

Answer 8

Hyperplasia at the site of red cell destruction (e.g. splenomegaly +/- hepatomegaly)

Question 9

What breakdown products of extravascular haemolysis can be measured?
What complications might they cause when released in excess?

Answer 9

Unconjugated bilirubin –> gallstones, jaundice

Urobilinogen in the urine

Question 10

What products of intravascular haemolysis might be detected?

Answer 10

Haemoglobin (haemoglobinaemia)
Methhaemalbuminaemia
Haemoglobinuria (pink urine, turns black on standing)
Haemosidinuria

Question 11

Name 5 causes of intravascular haemolysis

Answer 11

ABO incompatible blood transfusion
G6PD deficiency
Falciparum malaria (blackwater fever)
Paroxysmal nocturnal haemoglobinuria
Paroxysmal cold haemoglobinuria

Question 12

What investigations can be done to confirm haemolysis?

Answer 12

FBC
Blood film
Reticulocyte count
Serum haptoglobins
Serum unconjugated bilirubin
Urinary urobilinogen

Question 13

What are the signs on bloodfilm of a) membrane damage b) mechanical damage c) oxidative damage?

Answer 13

a) spherocytes
b) red cell fragments/schiscocytes
c) Heinz bodies

Question 14

What are the types of haemolysis as classified by the site of the red cell defect?

Answer 14

Premature destruction of normal red cells
Abnormal cell membrane
Abnormal cell metabolism
Abnormal haemoglobin

Question 15

Name different causes of warm and cold autoimmune haemolysis

What type of antibodies mediate both these disorders?

Answer 15

Warm (IgG):
Idiopathic
Autoimmune disorders
Lymphoproliferative disorders
Drugs (penicillins, methyldopa and quinine)
Infections
Cold (IgM):
Idiopathic
Infections (EBV, mycoplasma)
Lymphoproliferative disorders

Question 16

What is the treatment of autoimmune haemolytic disorders?

Answer 16

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

Question 17

Name the causes of alloimmune haemolysis

Answer 17

Immune response (antibody produced): immediate (IgM) or delayed (IgG) haemolytic transfusion reaction
Passive transfer of antibodies: haemolytic disease of the newborn

Question 18

Name five causes of mechanical haemolysis

Answer 18

Disseminated intravascular coagulation
Haemolytic uraemic syndrome
Thrombotic Thrombocytopenic Purpura
Leaking heart valve
Infections e.g. malaria

Question 19

What is a sign of mechanical haemolysis on blood film?

Answer 19

Schistocytes

Question 20

What is seen on blood film of burns related haemolysis? Why does this occur?

Answer 20

Microspherocytes

Red cells are sheared as they pass through damaged capillaries in severe burns

Question 21

Name three acquired causes of abnormal red cell membrane

Answer 21

Liver disease (Zieve's syndrome)
Vitamin E deficiency
Paroxysmal nocturnal haemoglobinuria

Question 22

What is Zieve’s syndrome?

What is seen on blood film?

Answer 22

Characterised by haemolysis, alcoholic liver disease and hyperlipidaemia.
Blood film: anaemia, polychromatic macrocytes, irregularly contracted cells

Question 23

What is a congenital cause of an abnormal red cell membrane that can cause haemolysis?

Answer 23

Hereditary spherocytosis