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Haematology > Haemolysis > Flashcards

Haemolysis Flashcards

1
Q

What is:
haemolysis
compensated haemolysis
haemolytic anaemia

A

haemolysis: premature RBC destruction i.e. shortened RBC survival

Compensated haemolysis: increased RBC destruction by increased RBC production i.e. Hb maintained (not a problem)

Haemolytic anaemia: increased RBC destruction excessds bone marrow capacity for RBC production i.e. Hb falls

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2
Q

Why are RBC’s particularly susceptable to damage? 3

A
  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) – can’t repair itself
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3
Q

what are the 2 consequences of haemolysis? why is this important?

A

¥ Erythroid hyperplasia (increased bone marrow red cell production)
¥ Excess red cell breakdown products eg billirubin (clinical features differ by aetiology and site of red cell breakdown)

-The consequences of haemolysis are used to detect haemolysis and then the cause is investigated

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4
Q

What are the two responses that the bone marrow produces in haemolysis?

A

1: reticulocytosis
- polychromasia
- can use methylene blue to detect RNA
- Automated reticulocyte counting can detect
- reticulocytosis is not diagnostic of haemolysis

2: erythroid hyperplasia

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5
Q

Classifying haemolysis:

How is haemolysis classified?

A

extravascular vs intravascular

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6
Q

What is extravascular vs intravascular haemolysis

A

Extravascular: Taken up by reticuloendothelial system (spleen and liver predominantly)

Intravascular: red cells destroyed within the circulation

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7
Q

Which is more common: intravascular or extravascular haemolysis?

A

extravascular

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8
Q

What are the clinical features of intravascular haemolysis?

A

• Hyperplasia at site of destruction =splenomegaly +/- hepatomegaly

• Release of protoporphyrin
= unconjugated bilirubinaemia – jaundice/gallstones
=urobilinogenuria

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9
Q

What are the clinical features of intravascular haemolysis?

A
  • Haemoglobinaemia (free Hb in circulation)
  • Methaemalbunimaemia – Hb bound to albumin
  • Haemoglobinuria: pink urine, turns black on standing (oxidising)
  • Haemosiderinura: Hb metabolised by kidneys and produces this
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10
Q

What is the difference between the products of extravascular vs intravascular haemolysis?

A

Extravascular:
-products are normal but are in excess

intravascular:

  • RBCs are destroyed in the circulation and spill their contents = abnormal products
  • may be fatal
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11
Q

What are the causes of extra vs intra vascular haemolysis?

What are the different causes for haemolysis in general?

A

Extravascular: essentially all other causes

intravascular:
¥	ABO incompatible blood transfusion
¥	G6PD deficiency
¥	Severe falciparum malaria (Blackwater Fever)
Rarer still PNH,PCH

Causes for haemolysis:

  • Premature destruction of normal RBC’s
  • Abnormal cell membrane
  • Abnormal RBC metabolism
  • Abnormal haemoglobin
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12
Q

What are the two different general causes for premature destruction of normal RBC’s?

A

Immune or mechanical

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13
Q

What are the two immune mechanisms that cause premature destruction of normal RBCs?

A
  • Autoimmune haemolysis

- alloimmune haemolysis

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14
Q

Autoimmune haemolysis:

  • what is this?
  • what test can be done?
  • what are the two different types?
A

• Autoimmune is pt has developed Ab to OWN RBCs (warm or cold)
o Can do direct coomb’s test to identify whether antibodies have been made
- warm or cold autoimmune haemolytic anaemia

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15
Q

Warm haemolytic anaemia:

  • what does this mean?
  • what type of antibody is involved?
  • what are the 5 causes?
A

Warm haemolytic anaemia is the most common type of autoimmune haemolytic anaemia and is mediated by IgG autoantibodies against RBC surface antigens (active at 37° C).

Causes:
Φ	Idiopathic (commonest)
Φ	Autoimmune disorders (SLE)
Φ	Lymphoproliferative disorders (CLL)
Φ	Drugs	(penicillins, etc)
Φ	Infections
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16
Q

Cold haemolytic anaemia:

  • what does this mean?
  • what type of antibody is involved?
  • what are the 3 causes?
A

This is RBC agglutination and hemolysis in peripheral cold exposed areas of the body. An IgM antibody binds to RBCs at 28-31oC.

Causes:
Φ Idiopathic
Φ Infections (EBV, mycoplasma)
Φ Lymphoproliferative disorders

17
Q

What is alloimmune haemolysis?

A

pt has developed Ab to foreign antigens e.g. transfused/fetus: can be antibody produced or passive transferral of Ab

18
Q

What is an example of antibody produced alloimmune haemolysis?

A

Haemolytic transfusion reaction
• Immediate (IgM) predominantly intravascular
• Delayed (IgG) predominantly extravascular

19
Q

What is an example of passive transfer of abody alloimmune haemolysis?

A

Haemolytic disease of the newborn
¥ Rh D
¥ ABO incompatibility
¥ Others eg anti-Kell

20
Q

What are 5 different causes for mechanical premature destruction of normal RBC’s?

A
  • Disseminated intravascular coagulation
  • Haemolytic uraemic syndrome (eg E. coli O157)
  • TTP: Thrombotic thrombocytopenic purpura
  • Leaking heart valve (abnormal flow through heart valve or mechanical valve) causes mechanical valve related microangiopathic haemolytic anaemia
  • Infections e.g. Malaria
  • burns related haemolysis
21
Q

what is DIC?

A

coagulation (especially thrombin) is activated inappropriately and in a diffuse way. This may lead to thrombosis in the subacute or chronic form but more often haemorrhage occurs as the clotting factors are exhausted. DIC is characterised by evidence of both thrombin and plasmin activation.

22
Q

What is TTP?

A

blood clots form in small blood vessels throughout the body - platelets are used up

23
Q

what is mechanical valve related microangiopathic haemolytic anaemia?

A

red cells fragmentatio as a result of mechanical damage itself

24
Q

What is microangiopathic haemolytic anaemia?

A

“Microangiopathic hemolytic anemia (MAHA)” is now used to designate any hemolytic anemia related to RBC fragmentation, occurring in association with small vessel disease

25
Q

What is the mechanism of burns related haemolysis?

A

red cells are sheared as they pass through damaged capillaries in severe burns
- microspherocytes

26
Q

What is seen on blood film for the mechanical premature destruction of normal RBC’s?

A

schistocytes = RBC fragments

27
Q

What is haemolytic uraemic syndrome?

A
  • acute renal failure
  • microangiopathic haemolytic anaemia
  • thrombocytopenia
28
Q

what are the 3 acquired causes of abnormal red blood cell membranes?

A
  • Liver disease (zieves’s syndrome): haemolysis, alcoholic liver disase and hyperlipidaemia
  • Vitamin E deficiency
  • Paroxysmal nocturnal haemoglobinuria
29
Q

What is seen on the blood film of zieve’s syndrome?

A
  • anaemia
  • polychromatic macrocytes
  • irregularly contracted cells

spur cells and acanthocytes

30
Q

What is the congenital cause of abnormal RBC membranes?

A

Hereditary spherocytosis

31
Q

what is the pathophysiology of hereditary spherocytosis?

A

• Reduced membrane deformability
• Increased transit time through spleen
• Oxidant environment in spleen causes extravascular red cell destruction
= chronic extravascular haemolysis

32
Q

What is the clinical course of hereditary spherocytosis? What is the inheritance?

A

Variable clinical course

-autosomal dominant

33
Q

Abnormal RBC metabolism:

  • what is the normal glucose metabolism pathways in RBCs?
  • how can problems arise in these pathways?
A
  • Glucose metabolism in RBC’s involves 2 pathways: one pathway is to harvest ATP and the other pathway is to harvest glutathione (anti-oxidant)
  • Problems can arise in either pathway

o even in the metabolic pathways of normal cells problems can arise if cells sufficiently stressed. E.g. by drugs Dapsone or salazopyrin or eating broad beans = oxidative damage

34
Q

What is glucose-6 phosphate dehydrogenase important for? what happens in G6PD deficiency?

A

glucose-6-phosphate dehydrogenase (G6PD) is the rate limiting enzyme in the pentose phosphate pathway. This is essential to maintain adequate amounts of reduced glutathione as it produced NADPH which ensure glutathione remains reduced.

In G6PD deficiency = RBC vulnerable to oxidative damage and thus liable to haemolysis.

35
Q

What is seen on blood film when the metabolism of the RBC is abnormal?

A

Keratocyte and irregularly contracted cells

36
Q

What is the cause for congenital abnormal haemoglobin causing haemolysis?

A
  • congenital

- sickle cell disease

37
Q

When you suspect a patient is haemolysing it is important to first confirm haemolytic state and then identify the cause.
What tests 6 are used to confirm haemolytic state?

A
  • FBC and blood film
  • reticulocyte count (how is bone marrow responding)
  • Serum unconjugated bilirubin (extravascular haemolysis)
  • Serum haptoglobins (appear reduced in haemolysis)
  • urinary urobilinogen (extravascular haemolysis)
38
Q

What is haptoglobin?

A

This is a plasma protein which binds free haemoglobin and then this is removed from circulation

Haematology (19 decks)

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