Haemolysis

Question 1

haemolysis definition

Answer 1

Premature red cell destruction
i.e. shortened red cell survival

Question 2

what is compensated haemolysis

Answer 2

Increased red cell destruction compensated by increased red cell production
i.e. Hb Maintained

Question 3

WHY ARE RED CELLS PARTICULARLY SUSCEPTIBLE TO DAMAGE?

Answer 3

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. Can’t generate new proteins once in the circulation (no nucleus)

Question 4

what is haemolytic anaemia (decompensated haemolysis)

Answer 4

Increased rate of red cell destruction exceeding bone marrow capacity for red cell production
i.e. Hb Falls

Question 5

consequences of haemolysis

Answer 5

Erythroid hyperplasia (increased bone marrow red cell production)

Excess red cell breakdown products eg bilirubin (clinical features differ by aetiology and site of red cell breakdown)

Question 6

what is the bone marrow response to haemolysis

Answer 6

1. reticulocytosis
2. erythroid hyperplasia

Question 7

extravascular haemolysis

Answer 7

Occursin the reticuloendothelial system (spleen and liver predominantly)

Question 8

intravascular haemolysis

Answer 8

Red cells destroyed within the circulation

Question 9

which is more common, extravascular or intravascular haemolysis

Answer 9

extravascular

Question 10

intravascular haemolysis is potentially lifethreatening, true or false

Answer 10

true

Question 11

intravascular haemolysis causes

Answer 11

• ABO incompatible blood transfusion
• G6PD deficiency
• severe falciparum malaria
• rare diseases - PNH, PCH

Question 12

haemolysis investigations - confirming haemolytic state

Answer 12

1. confirm haemolytic state
   - FBC and blood film
   - Reticulocyte count
   - Serum unconjugated bilirubin
   - Serum haptoglobins
   - Urinary urobilinogen

Question 13

haemolysis investigations

Answer 13

1. confirm haemolytic state
2. Identify cause

Question 14

haemolysis investigations - blood film. what might we see?

Answer 14

Membrane damage (spherocytes)

Mechanical damage (red cell fragments)

Oxidative damage (Heinz bodies)

Others e.g.. HbS (sickle cells)

Question 15

acquired causes of haemolysis

Answer 15

autoimmune haemolysis

alloimmune haemolysis

Question 16

autoimmune haemolysis - warm or cold antibody

warm (Ig__)
cold (Ig__)

Answer 16

warm IgG
cold IgM

Question 17

haemolytic disease of the newborn is an example of _____immune haemolysis

Answer 17

alloimmune

Question 18

causes of acquired haemolysis - mechanical red cell destruction

Answer 18

Disseminated intravascular coagulation
Haemolytic uraemic syndrome (eg E. coli O157)
TTP
Leaking heart valve
Infections e.g. Malaria

Question 19

causes of acquired haemolysis - membrane defects (All very rare)

Answer 19

Liver Disease (Zieve’s Syndrome)

Vitamin E deficiency

Paroxysmal Nocturnal Haemoglobinuria

Question 20

genetic causes of haemolysis - abnormal red cell metabolism

Answer 20

failure to cope with oxidant stress (G6PD deficiency)

failure to generate ATP: metabolic processes fail

NB Even the metabolic pathways of normal cells if sufficiently stressed e.g.by dapsone or salazopyrin can get oxidative damage

Question 21

genetic causes of haemolysis - abnormal haemoglobins

Answer 21

sickle cell disease (Hb S)