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Year 3 - 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 particularly susceptible to damage?

A

Need to have biconcave shape to transit the circulation successfully

They have limited metabolic reserve and rely exclusively on glucose metabolism for energy (no mitochondria)

Can’t generate new proteins once in circulation (no nucleus)

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3
Q

What is compensated haemolysis?

A

Increased red cell destruction compensated by increased red cell production (Hb maintained)

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4
Q

What is decompensated haemolysis (haemolytic anaemia)?

A

Increased rate of red cell destruction exceeding bone marrow capacity for red cell production (Hb falls)

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5
Q

What are the two main consequences of hamolysis?

A
  1. Erythroid hyperplasia (increased bone marrow red cell breakdown)
  2. Excess red cell breakdown products e.g. bilirubin (clinical features differ by aetiology and site of red cell breakdown)
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6
Q

What is the bone marrow response to haemolysis?

A

Erythroid hyperplasia
Reticulocytosis

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7
Q

Are reticulocytes nucleated cells?

A

NO!!!!

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8
Q

Reticulocytes are not diagnostic of haemolysis, they are also found when?

A

In response to bleeding
Iron therapy in iron deficiency anaemia

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9
Q

A blood film with reticulocytes will be described as?

A

Polychromatic because there is ribosomal RNA in reticulocytes

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10
Q

What stain can you use for reticulocytes?

A

Supravital stain staining ribosomal RNA (new methylene blue)

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11
Q

What happens in extravascular haemolysis?

A

Hyperplasia at site of destruction (splenomegaly +/- hepatomegaly)

Taken up by reticuloendothelial system (spleen and liver predominantly)

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12
Q

What is commoner - extravascular or intravascular haemolysis?

A

Extravascular haemolysis

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13
Q

What happens to end products in extravascular haemolysis?

A

Release of protoporphyrin
- Unconjugated bilirubinaemiea (jaundice, gall stones)
- Urobilinogenuria

NORMAL PRODUCTS IN EXCESS

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14
Q

What is intravascular haemolysis?

A

Red cells destroyed in circulation spilling their contents

ABNORMAL PRODUCTS

may be life threatening

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15
Q

What 4 signs can be seen in intrasvascular haemolysis?

A

Haemoglobinaemia (Free Hb in circulation)
Methaemalbuminaemia
Haemoglobinuria (pink urine, turns black on standing)
Haemosiderinuria

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16
Q

What are causes of intravascular haemolysis?

A

ABO incompatible blood transfusion
G6PD deficiency
Severe falciparum malaria (blackwater fever)
Rarer still PNH, PCH

17
Q

What tests should you do to confirm haemolytic state?

A

FBC (+ blood film)
Retiulocyte count
Serum unconjugated bilirubin
Serum haptoglobins
Urinary urobilinogen

18
Q

How do you identify cause of haemolysis?

A

History + exam (genetic / acquired)
Blood film
- Membrane damage (spherocytes)
- Mechanical damage (red cell fragments)
- Oxidative damage (Heinz bodies)
- Others e.g. HbS (sickle cells)

Specialist investigations (Direct Coombs test and others)

19
Q

If you classify haemolysis by site of red cell defect, what would be the 4 categories?

A

Premature destruction of normal red cells (immune or mechanical)
Abnormal cell membrane
Abnormal red cell metabolism
Abnormal haemoglobin

Congenital vs. acquired

20
Q

What are acquired immune causes of haemolysis?

A

Autoimmune haemolysis
Alloimmune haemolysis

21
Q

What are examples of autoimmune haemolysis?

A

Warm or cold autoantibody

Warm (IgG)
Cold (IgM)

22
Q

Warm autoimmune haemolysis has what antibody?

A

IgG

23
Q

Cold autoimmune haemolysis has what antibody?

A

IgM

24
Q

What are causes of warm autoimmune haemolysis?

A

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

25
Q

What are causes of cold autoimmune haemolysis?

A

Idiopathic
Infections (EBV, mycoplasma)
Lymphoproliferative disorders

26
Q

What does Direct Coombs test test for? How does it work?

A

Autoimmune haemolysis

27
Q

What are causes of alloimmune haemolysis?

A

Immune response (antibody produced)
- Haemolytic transfusion reaction (immediate (IgM) predominantly intravascular; delayed (IgG) predominately extravascular)

Passive transfer of antibody
- Haemolytic disease of the newborn (RhD, ABO incompatibility, others e.g. Anti-Kell)

28
Q

What are causes of mechanical red cell destruction?

A

Disseminated intravascular coagulation (DIC)
Haemolytic uraemic syndrome (e.g. E. coli 0157)
TTP
Leaking heart valve
Infections e.g. Malaria

29
Q

What kind of haemolysis does a mechanical valve cause?

A

Microangiopathic haemolytic anaemia (MAHA)

Red cell fragmentation as a result of mechanical (Extrinsic) damage

30
Q

What can be seen in burns related haemolysis?

A

Microspherocytes

31
Q

What are causes of acquired membrane defect causes of haemolysis?

A

ALL VERY RARE

Liver disease (Zieve’s syndrome)
Vitamin E deficiency
Paroxysmal nocturnal haemoglobinuria

32
Q

What is Zieve’s syndrome and what is seen?

A
33
Q

What are genetic causes of abnormal cell membrane haemolysis?

A

Red cell membrane abnormalities
- Reduced membrane deformability
- Increased transit time through spleen
- Oxidant environment in spleen causes extravascular red cell destruction
- Hereditary spherocytosis

34
Q

What genetic causes exist for abnormal red cell metabolism haemolysis?

A

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

35
Q

Dapsone therapy can cause what changes to blood cells?

A
36
Q

What genetic causes of haemolysis exist whereby the problem is abnormal haemoglobin?

A

Sickle cell disease (HbS) - affects physical properties of haemoglobin (abnormal polymerisation) resulting in shortened red cell survival
- Caused by a point mutation in beta globin chain
- Disease has variable clinical severity
- Trait asymptomatic

37
Q

What bone marrow and blood changes would you see in beta thalassaemia major?

A
38
Q

What happens in HbH disease (a form of alpha thalassaemia) and what is seen on blood film?

A

Year 3 - Haematology (35 decks)

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