Haemolysis

Question 1

What is haemolysis?

Answer 1

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

Question 2

Why are red cells particularly susceptible to damage?

Answer 2

Biconcave shape
Limited metabolic reserve; rely on glycolysis (no mitochondria)
Can’t generate new protein once circulating (no nucleus)

Question 3

What is meant by compensated haemolysis?

Answer 3

Increased red cell destruction followed by increased red cell production
i.e. Hb is maintained

Question 4

What is decompensated haemolysis, AKA haemolytic anaemia?

Answer 4

Increased red cell destruction exceeding bone marrow capacity level of red cell production
i.e. Hb not maintained

Question 5

What are the consequences of haemolysis?

Answer 5

Erythroid hyperplasia (increased bone marrow RBC turnover)
Excess RBC breakdown products (bilirubin)

Question 6

What are the 2 bone marrow responses to haemolysis?

Answer 6

Reticulocytosis

Erythroid hyperplasia

Question 7

Reticulocytes in the circulation are diagnostic of haemolysis. True/False?

Answer 7

False

Can be present in bleeding, iron therapy, anaemia etc.

Question 8

What are the 2 classifications of haemolysis that make it easier for us to identify the cause?

Answer 8

Extravascular (more common)

Intravascular

Question 9

What does extravascular haemolysis involve?

Answer 9

Hyperplasia at site of destruction (spleen and liver)
Release of protoporphyrin, resulting in unconjugated jaundice
i.e. normal blood products in excess

Question 10

What does intravascular haemolysis involve?

Answer 10

Red cells destroyed in the circulation and spill contents

i.e. abnormal products

Question 11

What are the 4 main features/products of intravascular haemolysis?

Answer 11

Haemoglobinaemia (free Hb in blood)
Methaemalbuminaemia
Haemoglobinuria (pink urine turns black)
Haemosiderinuria

Question 12

What investigations are done to confirm haemolytic state?

Answer 12

FBC + blood film
Reticulocyte count
Serum unconj. bilirubin
Serum haptoglobin
Urinary urobilinogen

Question 13

What might be seen on a blood film in haemolysis when identifying a cause?

Answer 13

Membrane damage (spherocytes)
Mechanical damage (red cell fragments)
Oxidative damage (Heinz bodies)
Sickle cells

Question 14

What is the direct Coomb’s test used for? What type of anaemia is it diagnostic of?

Answer 14

Identifies antibody (and Complement) bound to red cells
Autoimmune haemolytic anaemia

Question 15

List some causes of mechanical red cell destruction

Answer 15

Disseminated intravascular coagulation
Haemolytic uremic syndrome
Leaky heart valve
Infection

Question 16

Give the most common cause of intravascular haemolysis

Answer 16

ABO incompatible blood transfusion

Question 17

List the classifications of haemolysis by red cell defect

Answer 17

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

Question 18

Premature destruction of normal red cells can be split into two main causes. What are they?

Answer 18

Immune (auto or alloimmune haemolysis)

Acquired (mechanical red cell destruction)

Question 19

Autoimmune haemolysis can be divided by the antibody made. List the types.

Answer 19

Warm IgG autoantibody

Cold IgM autoantibody

Question 20

List causes of warm IgG autoantibody

Answer 20

Idiopathic
Autoimmune disease (SLE)
Lymphoproliferative 
Drugs (penicillin)
Infections

Question 21

List causes of cold IgM autoantibody

Answer 21

Idiopathic
Infections (EBV, mycoplasma)
Lymphoproliferative

Question 22

List aetiology of alloimmune haemolysis

Answer 22

Immune response (antibody produced) causing a haemolytic transfusion reaction
Passive transfer of antibody causing haemolytic disease of newborn (e.g. RhD or ABO incomplete)

Question 23

Acute haemolytic transfusion reaction involves Ig? antibody and is usually an intravascular/extravascular haemolysis

Answer 23

Acute haemolytic transfusion reaction involves IgM antibody and is usually an intravascular haemolysis

Question 24

Delayed haemolytic transfusion reaction involves Ig? antibody and is usually an intravascular/extravascular haemolysis

Answer 24

Delayed haemolytic transfusion reaction involves IgG antibody and is usually an extravascular haemolysis

Question 25

List causes of acquired mechanical red cell destruction

Answer 25

``` Disseminated intravascular coagulation Haemolytic ureamic syndrome e.g E.Coli 0157 TTP Leaking heart valve Infections e.g. malaria ```

Question 26

Give acquired causes of abnormal cell membrane

Answer 26

``` Liver disease (Zieves syndrome) Vitamin E deficiency Paroxysmal nocturnal haemoglobinuria ```

Question 27

What is the main cause of a congenital abnormal cell membrane?

Answer 27

Heridatory spherocytosis

Question 28

What is the pathophysiolgy behind heridatory spherocytosis?

Answer 28

Increased transit time through the spleen | Oxidant environment in spleen leads to extravascular red cell destruction

Question 29

Outline management options for heridatory spherocytosis

Answer 29

Folic acid to sustain erythropoeisis | Spleenectomy if young to help growth

Question 30

List aetiology of abnormal red cell metabolism

Answer 30

Failure to cope with oxidant stress (G6PD deficiency) | Failure to generate ATP (metabolic processes fail)

Question 31

What is the main cause of abnormal haemoglobin?

Answer 31

Sickle cell disease

Question 32

What is the pathophysiolgy behind sickle cell disease?

Answer 32

Sickle cell disease trait produces HbS causing abnormal polymerisation leading to shortened red cell survival

Question 33

What is a characteristic sign of autoimmune haemolytic anaemia on film?

Answer 33

Teardrop red blood cells

Question 34

What do spherocytes look like on film?

Answer 34

Sphere-shaped cells | Lack of pallor

Question 35

How should an autoimmune haemolytic anaemia be treated?

Answer 35

``` Steroid therapy (prednisolone) Folic acid ```