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Haematology > Haemolysis > Flashcards

Haemolysis Flashcards

1
Q

What is haemolysis?

A

Premature red cell destruction

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2
Q

Why are red cells susceptible to damage?

A

Biconcave shape to transmit the circulation successfully
Limited metabolic reserve and rely on glucose for energy
Can’t generate new proteins once in circulation

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3
Q

What is compensated haemolysis?

A

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

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4
Q

What is haemolytic anaemia?

A

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

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5
Q

What are the consequences of haemolysis?

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)
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6
Q

What is the bone marrow response to haemoylsis?

A

Reticulocytosis

Erythroid hyperplasia

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7
Q

How is haemolysis classified?

A

Extravascular- Taken up by reticuloendothelial system (spleen and liver predominantly)
Intravascular- Red cells destroyed within the circulation

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8
Q

What is seen in extravascular red cell destruction?

A

Hyperplasia at site (spleen+-hepatomegaly)
Release of protoporphyrin: unconjugated bilirubinaemia (jaundice, gall stones), urobilinogenuria
Normal products in excess

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9
Q

What is see in intravascular red cell destruction?

A

Red cells are destroyed in the circulation spilling their contents. This explains the pathophysiology
Haemoglobinaemia (free Hb in circulation)
Methaemalbuminaemia
Haemoglobinuria: pink urine, turns black on standing
Haemosiderinuria
Abnormal products
May be life threatening

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10
Q

What are the causes of intra and extravascular haemolysis?

A 
Intra:
ABO incompatible blood transfusion
G6PD deficiency
Severe falciparum malaria (Blackwater Fever)
Rarer still PNH,PCH
Extra: all other causes
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11
Q

What Ix is required in haemolysis?

A

Confirm haemolytic state: FBC, film, reticulocyte count, serum unconjugated bilirubin, serum haptoglobins, urinary urobilinogen
Identify cause

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12
Q

What may be seen on the blood film in haemolysis?

A 
Membrane damage (spherocytes)
Mechanical damage (red cell fragments)
Oxidative damage (Heinz bodies)
Others e.g.. HbS (sickle cells)
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13
Q

What is another classification of haemolysis?

A 
By site of defect:
Premature destruction of normal red cells (immune or mechanical)
Abnormal cell membrane
Abnormal red cell metabolism
Abnormal haemoglobin
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14
Q

What are the immune causes of acquired haemolysis?

A

AI haemolysis, alloimmune haemolysis

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15
Q

What are the causes of warm (IgG) autoantibody in AI haemolysis?

A

Idiopathic (commonest)
Autoimmune disorders (SLE)Lymphoproliferative disorders (CLL)
Drugs (penicillins, etc)Infections

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16
Q

What are the causes of cold(IgM) autoantibody in AI haemolysis?

A

Idiopathic
Infections (EBV, mycoplasma)
Lymphoproliferative disorders

17
Q

What does the Direct Coombs’ Test do?

A

Identifies antibody and complement bound to own red cells

18
Q

What are the causes of alloimmune haemolysis?

A 
Immune response (Ab mediated)- haemolytic transfusion reaction: immediate (IgM) predominantly intra, delayed (IgG) extra
Passive transfer of Ab: haemolytic disease of newborn: Rh D, ABO incompatibility, other
19
Q

What are the mechanical causes of acquired haemolysis?

A 
Disseminated intravascular coagulation
Haemolytic uraemic syndrome (eg E. coli O157)
TTP
Leaking heart valve
Infections e.g. Malaria
Burns
20
Q

What is seen on the film in burns related haemolysis?

A

Microspherocytes

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

21
Q

What are the membrane defect causes of acquired haemolysis (rare)?

A 
Liver Disease (Zieve’s Syndrome)
Vitamin E deficiency
Paroxysmal Nocturnal Haemoglobinuria
22
Q

What is Zieve’s syndrome?

A

Haemolysis
Alcoholic liver disease
Hyperlipidaemia

23
Q

What is seen on the film in Zieve’s?

A

Anaemia
Polychromatic macrocytes
Irregularly contracted cells

24
Q

What are the genetic red cell membrane abnormalities that cause haemolysis?

A

Reduced membrane deformability
Increased transit time through spleen
Oxidant environment in spleen causes extravascular red cell destruction
Hereditary Spherocytosis

25
Q

What are the genetic abnormal red cell metabolism problems that cause haemolysis?

A

Failure to cope with oxidant stress (G6PD deficiency)
Failure to generate ATP: metabolic processes fail
Even the metabolic pathways of normal cells if sufficiently stressed e.g.by dapsone or salazopyrin can get oxidative damage

26
Q

What are the genetic abnormal Hb problems that cause haemolysis?

A

Sickle cell disease (Hb S): affects physical properties of haemoglobin (abnormal polymerisation) resulting in shortened red cell survival

Haematology (23 decks)

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