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Flashcards in Haemolysis Deck (30)
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1
Q

What is haemolysis?

A

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

2
Q

Why are RBCs susceptible to damage?

A
  1. They need to have a biconcave shape to circulate successfully 2. They have limited metabolic reserve and rely solely on glycolysis for energy 3. Can’t generate new proteins once in the circulation (no nucleus)
3
Q

What is compensated haemolysis?

A

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

4
Q

What is haemolytic anaemia?

A

Decompensated haemolysis - increased rate of red cell destruction exceeding bone marrow capacity for red cell production i.e. Hb falls

5
Q

What are the consequences of haemolysis?

A

Erythroid hyperplasia - increased bone marrow red cell production Excess red cell breakdown products e.g. bilirubin

6
Q

It’s not possible to directly measure red cell survival routinely so how is haemolysis identified?

A

Rely on detecting the consequences of haemolysis and then investigating the cause - increased red cell production, detection of breakdown products

7
Q

What is the bone marrow response to haemolysis?

A

Reticulocytosis and erythroid hyperplasia i.e. making lots of new immature RBCs

8
Q

What would the blood film of a patient with haemolysis feature?

A

Polychromasia due to ribosomal RNA

9
Q

What is automated reticulocyte counting?

A

Ribosomal RNA is labelled with a fluorochrome and fluorescent cells are counted

10
Q

How is haemolysis classified?

A

Extravascular and intravascular

11
Q

What is the basic pathology behind extravascular and intravascular haemolysis respectively?

A

Extravascular - RBCs taken up by reticuloendothelial system (spleen and liver) Intravascular - RBCs destroyed within the circulation

12
Q

Where does hyperplasia occur in extravascular haemolysis and what happens as a result of EV haemolysis?

A

More common than intravascular. Hyperplasia at site of destruction (e.g. splenomegaly). Release of protoporphyrin - unconjugated bilirubinaemia (jaundice and gall stones), urobilinogenuria NORMAL products but in excess

13
Q

What is the underlying mechanism of intravascular haemolysis and what happens as a result of intravascular haemolysis?

A

Red cells are destroyed in the circulation spilling their contents causing haemoglobinaemia (free Hb in circulation), methaemalbuminaemia, haemoglobinuria (pink urine, turns black on standing) and haemosiderinuria. ABNORMAL products - intravasuclar haemolysis may be life threatening

14
Q

What are some of the intravascular causes of haemolysis?

A

ABO incompatible blood transfusion, G6PD deficiency, severe falciparum malaria (blackwater fever)

15
Q

How is haemolysis investigated?

A

Confirm haemolytic state - FBC, reticulocyte count, serum unconjugated bilirubin, serum haptoglobins, urinary urobilinogen Identify cause - history and examination, blood film (spherocytes, red cell fragments, Heinz bodies, sickle cells), direct Coombs’ test

16
Q

What is another way of classifying haemolysis (other than intra vs extravascular)?

A

By site of red cell defect - congenital vs acquired

17
Q

What are the causes of acquired immune haemolysis?

A

Autoimmune haemolysis or alloimmune haemolysis

18
Q

There are 2 types of autoantibody possible in autoimmune haemolysis, what are these?

A

Warm - IgG Cold - IgM

19
Q

What conditions is the warm (IgG) autoantibody for autoimmune haemolysis seen in?

A

Autoimmune disorders e.g. SLE, lymphoproliferative disorders e.g. CLL, drugs e.g. penicillins, infections

20
Q

What conditions is the cold (IgM) autoantibody for autoimmune haemolysis seen in?

A

Infections e.g. EBV, mycoplasma Lymphoproliferative disorders e.g. CLL

21
Q

What does a direct Coombs’ test do?

A

Identifies antibody (and complement) bound to own red cells

22
Q

What can cause alloimmune haemolysis?

A

Immune response (antibody produced) - haemolytic transfusion reaction; immediate (IgM) predominantly intravascular or delayed (IgG) predominantly extravascular Passive transfer of antibody - haemolytic disease of the newborn; RhD, ABO incompatibility

23
Q

What are the causes of acquired mechanical haemolysis?

A

Disseminated intravascular coagulation, haemolytic uraemic syndrome (e.g. E.coli 0157), TTP, leaking heart valve, infections e.g. malaria

24
Q

What would appear on blood film in a patient with burns related haemolysis?

A

Microspherocytes, red cells are sheared as they pass through the damaged capillaries. Only seen therefore in severe burns

25
Q

What would cause acquired haemolysis due to abnormal cell membrane?

A

Very rare cause of acquired haemolysis. Liver disease (Zieve’s syndrome), vitamin E deficiency, paroxysmal nocturnal haemoglobinuria

26
Q

What are the features of Zieve’s syndrome?

A

Haemolysis, alcoholic liver disease and hyperlipidaemia are the main features Anaemia, polychromatic macrocytes and irregularly contracted cells

27
Q

What is the most common genetic cause of haemolysis?

A

Hereditary spherocytosis - abnormal red cell membrane

28
Q

What is the mechanism behind abnormal red cell metabolism as a genetic cause of haemolysis?

A

Failure to cope with oxidant stress (G6PD deficiency) -> failure to generate ATP (metabolic processes fail)

29
Q

What is the main cause of abnormal haemoglobin causing genetic haemolysis?

A

Sickle cell disease - affects physical properties of haemoglobin resulting in shortened red cell survival

30
Q

What causes sickle cell disease?

A

A point mutation in beta globin chain