Haemolysis

Question 1

What is haemolysis?

Answer 1

Premature RBC destruction

Question 2

What makes RBCs susceptible to damage?

Answer 2

Biconcave shape
Lack of mitochondria
Lack of nucleus

Question 3

Can haemolysis be compensated for?

Answer 3

Yes by bone marrow up-regulation.

Only works for a certain degree of haemolysis.

Question 4

What are the consequences of excess haemolysis?

Answer 4

Erythroid hyperplasia

Excess RBC breakdown products

Question 5

How does the bone marrow respond to haemolysis?

Answer 5

Reticulocytosis

In the more chronic cases, there will be erythroid hyperplasia.

Question 6

What is the biggest source of cell production in adults?

Answer 6

Iliac crests

Question 7

What are the 2 types of haemolysis?

Answer 7

Extravascular (most common)

Intravascular

Question 8

Where are cells destroyed in extravascular haemolysis?

Answer 8

Usually in the spleen/liver.

Question 9

Where are cells destroyed in intravascular haemolysis?

Answer 9

Usually within the circulation.

Question 10

How does extravascular haemolysis present?

Answer 10

Splenomegaly +/- hepatomegaly
Jaundice
Gallstones
Bilirubinuria

Question 11

What form of bilirubin is produced from the breakdown of RBCs?

Answer 11

Unconjugated bilirubin

Question 12

How does intravascular haemolysis present?

Answer 12

Pink urine (due to haemoglobinuria)

Upon blood testing there will be haemoglobinuria and methaemalbuminaemia

Urine may also contain haemosiderins

Question 13

Which form of haemolysis is a potentially life-threatening presentation?

Answer 13

Intravascular haemolysis

Question 14

What is a key difference between extravascular and intravascular haemolysis?

Answer 14

In extravascular haemolysis, products are normal but present in excess.

In intravascular haemolysis, abnormal products are formed.

Question 15

What are the 3 causes of intravascular haemolysis?

Answer 15

ABO incompatibility
G6PD deficiency
Severe falciparum malaria

All other causes of haemolysis produce the extravascular form.

Question 16

What is haptoglobin?

Answer 16

A serum protein that binds free haemoglobin.

This is reduced/undetectable if free haemoglobin is present - as it all becomes bound.

Question 17

What is autoimmune haemolysis?

Answer 17

The development of IgG or IgM against RBCs.

It is usually of idiopathic origin.

Question 18

What is alloimmune haemolysis?

Answer 18

The presence of IgM which causes immediate intravascular haemolysis and IgG which causes delayed extravascular haemolysis.

Can occur in haemolytic transfusion reactions and haemolytic disease of the newborn.

Question 19

What are causes of mechanical cell destruction?

Answer 19

DIC
HUS
TTP
Leaking heart valves
Infection

Question 20

What is the issue in those with membrane defects?

Answer 20

There is reduced membrane deformability, with increased transit time through the spleen, making these cells more likely to undergo extravascular haemolysis.

Question 21

What can cause RBC membrane defects?

Answer 21

Liver disease
Vitamin E deficiency
Hereditary spherocytosis
Paroxysmal nocturnal haemoglobinuria

Question 22

What is the role of G6PD?

Answer 22

Provides antioxidants to protect cell.

Provides ATP for an energy source.

Question 23

What 2 therapies can cause normal cells to undergo oxidative stress?

Answer 23

Dapsone

Salazopyrin