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Haematology > Haemolysis > Flashcards

Haemolysis Flashcards

1
Q

Define haemolysis

A

Premature red cell destruction - shortened survival

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2
Q

What makes red cells susceptible to haemolysis?

A

Shape
Limited metabolic reserve
Cannot generate new proteins

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3
Q

What is haemolytic anaemia?

A

Increased rate of red cell destruction exceeding bone marrow capacity causing Hb to fall

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4
Q

How does the bone marrow respond to haemolysis?

A

Reticulocytosis

Erythroid Hyperplasia

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5
Q

Describe reticulocytosis

A

Most immature red cells in the circulation, no nucleus but some RNA - polychromatic

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6
Q

What are the two types of haemolysis?

A

Extravascular

Intravascular

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7
Q

What is extravascular haemolysis?

A

Taken up by reticuloendothelial system - spleen and liver, hyperplasia occurs at site of destruction and there is release of normal products

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8
Q

What are the normal products released in extravascular haemolysis?

A

Protoporphyrin - unconjugated bilirubinaemia (jaundice and gallstones)
Urobilinogenuria

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9
Q

What happens in intravascular haemolysis?

A

Red cells destroyed within the circulation and spill their contents

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10
Q

Name the consequence of red cells spilling their contents

A

Haemoglobinaemia
Methaemalbumin
Haemoglobinuria (pink urine turns black on standing)
Haemosiderinuria (iron protein)

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11
Q

What can cause intravascular haemolysis?

A 
ABO incompatibility 
G6PD deficiency 
Falciparum Malaria 
Paroxysmal cold haemoglobinuria 
Paroxysmal nocturnal haemoglobinuria
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12
Q

What investigations are done in suspected haemolysis?

A 
FBC 
Blood film 
Reticulocyte count 
Serum unconjugated bilirubin and haptoglobin 
Urinary urobilinogen
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13
Q

What might be seen on a blood film of haemolysis?

A

Membrane damage - spherocytes
Mechanical damage - red cell fragments
Oxidative damage - Heinz bodies
HbS - sickle cell

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14
Q

Name the test used to detect red cell antibodies

A

Coomb’s Test

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15
Q

Name the four types of red cell defect

A
  1. premature destruction of normal red cell (immune or mechanical)
  2. abnormal cell membrane
  3. abnormal cell metabolism
  4. abnormal haemoglobin
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16
Q

What are the two types of immune mediated premature destruction?

A

Autoimmune

Alloimmune

17
Q

Describe autoimmune haemolysis

A

Autoantibodies to red cells
Warm IgG
Cold IgM

18
Q

What can cause warm IgG?

A

Idiopathic, autoimmune disorders, lymphoproliferative, infection, drugs

19
Q

What can cause cold IgM?

A

Idiopathic, infections - EBV, mycoplasma, lymphoproliferative

20
Q

What test can be used in Immune premature destruction?

A

Direct Coombs test

21
Q

Name two types of alloimmune haemolysis

A

Haemolytic transfusion reaction

Haemolytic disease of the newborn

22
Q

Name the causes of mechanical premature destruction

A

DIC, HUS, TTP, Malaria, leaky heart valve, burns

23
Q

Why does red cell destruction happen in burns?

A

Red cells are sheared as they pass through the damaged capillaries - microspherocytes

24
Q

Name three acquired membrane defects

A

Liver disease
Vitamin E deficiency
Paroxysmal nocturnal haemoglobinuria

25
Q

What is the most common congenital membrane defect?

A

Hereditary spherocytosis

26
Q

What happens in hereditary spherocytosis?

A

Reduced membrane deformability, increased transmit time through spleen, oxidant environment in spleen causes extravascular red cell destruction

27
Q

What happens in G6PD deficiency?

A

Failure to cope with oxidant stress

Failure to generate ATP

28
Q

Does there always have to be a G6PD deficiency for abnormal red cell metabolism to occur?

A

No - can occur due to increase oxidative stress due to drugs e.g. Dapsone

29
Q

Describe the pathology of oxidation

A

Denatured Hb forms inclusion (Heinz bodies), this causes the spleen to take ‘bites’ out of the cell in an effort to remove them and thus forms irregular contracted cells and keratocytes

30
Q

What is the most common haemoglobinopathy to cause haemolysis?

A

Sickle cell

Haematology (18 decks)

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