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Haematology > Haemolysis > Flashcards

Haemolysis Flashcards

1
Q

What two responses does the bone marrow have to haemolysis?

A

Reticulocytosis

Erythroid hyperplasia

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2
Q

What two classifications of haemolysis are there?

A

Intravascular

Extravascular

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3
Q

Where does extravascular haemolysis occur?

A

Liver and spleen predominantly

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4
Q

Why are red cells so susceptible to damage?

A
  1. Biconcave shape allows ease of transport - membrane abnormalities altering this shape leave them susceptible to damage
  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)
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5
Q

What is compensated haemolysis?

A

Increased red cell destruction compensated by increased red cell production

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6
Q

What is uncompensated haemolysis?

A

Haemolytic anaemia - Increased rate of red cell destruction exceeding bone marrow capacity for red cell production

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7
Q

What is the more common type of haemolysis (intra or extravascular)?

A

Extravascular

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8
Q

What sign on examination may indicate extravascular haemolysis?

A

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

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9
Q

What are the causes of intravascular haemolysis?

A

ABO incompatible blood transfusion
G6PD deficiency
Severe falciparum malaria (Blackwater Fever)
Rarer still paroxysmal nocturnal haemoglobinuria or paroxysmal cold haemoglobinuria

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10
Q

What are the key haematological features of haemolysis?

A 
Raised unconjugated bilirubin
Reduced haptoglobin
Raised LDH
Raised urobilinogen
Reticulocytosis and polychromasia
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11
Q

What happens to serum haptoglobins in someone who is haemolysing?

A

Numbers reduce

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12
Q

What investigations should be done to identify the cause of haemolysis?

A

History and examination
Blood film
Specialist investigations e.g. direct Coombs test

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13
Q

What conditions is IgG autoimmune haemolysis associated with?

A

Autoimmune disorders e.g. SLE

Lymphoproliferative disorders e.g. CLL

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14
Q

What conditions is IgM autoimmune haemolysis associated with?

A

Infecctions e.g. EBV

Lymphoproliferative disorders

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15
Q

What two examples of alloimmune haemolysis are there?

A

Immune response/antibodies formed i.e. haemolytic transfusion reaction
Passive transfer of antibody i.e. haemolytic disease of the newborn

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16
Q

What is the antibody response and site of reaction in a haemolytic transfusion reaction?

A

IgM - immediate, predominantly intravascular

IgG - delayed, predominantly extravascular

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17
Q

What are some causes of mechanical red cell destruction??

A 
Disseminated intravascular coagulation
Haemolytic uraemic syndrome (eg E. coli O157)
Thrombotic thrombocytopenic purpura
Leaking heart valve
Infections e.g. Malaria
Severe burns
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18
Q

How do severe burns cause mechanical red cell damage?

A

Red blood cells are sheared as they pass through the damaged capillaries

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19
Q

What is Zieves syndrome and what kind of haemolysis does it cause?

A

A cause of damage to the red cell membrane in patients who have severe alcoholic liver disease and hyperlipidaemia

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20
Q

How do red cell membrane abnormalities cause haemolysis?

A

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

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21
Q

What are the waste products/results of extravascular haemolysis?

A 
Release of protoporphyrin
Unconjugated bilrubinaemia
 Jaundice
 Gall stones
Urobilinogenuria

i.e. all normal haemolytic products in excess

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22
Q

What is chronic haemolytic anaemia often associated with?

A

Folate deficiency

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23
Q

What is haptoglobin?

A

A protein that binds free haemoglobin in the bloodstream that is then removed by reticuloendothelial cells

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24
Q

What is the only intrinsic red cell condition that is acquired?

A

Paroxysmal nocturnal haemoglobinuria

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25
Q

What three locations might an inherited condition affect the red cell?

A

Cell membrane
Cytoplasm
Haemoglobin

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26
Q

What inherited condition affect the cell membrane?

A

Spherocytosis

Elliptocytosis

27
Q

What is the mode of inheritance for spherocytosis and elliptocytosis?

A

Autosomal dominant

28
Q

What is the problem in elliptocytosis and spherocytosis?

A

A problem with the spectrin or anchorin proteins on the cell membrane
Reduced cell lifespan due to normal shape, causing trapping in the spleen causing premature phagocytosis by splenic macrophages

29
Q

Which is more severe and common: elliptocytosis or spherocytosis?

A

Spherocytosis

30
Q

How is elliptocytosis treated?

A

Usually mild so just left

31
Q

How is spherocytosis treated?

A

Splenectomy
Folate supplementation
Vaccinations prior to splenectomy
Prophylactic antibiotics

32
Q

What inherited condition affects the red cell cytoplasm?

A

Glucose-6-dehydrogenase deficiency

33
Q

What is the problem in G-6-D deficiency?

A

The red cells are lacking the ability to form NADPH, which usually works with glucothione to protect the cell from oxidative damage

34
Q

What is the mode of inheritence in glucose-6-dehydrogenase deficiency?

A

X-linked

35
Q

What are the two possible clinical sydromes of glucose-6-dehydrogenase deficiency?

A

Chronic haemolytic anaemia or acute haemolytic episodes

36
Q

What is the usual clinical syndrome of G-6-D deficiency?

A

Acute haemolytic episodes caused by a precipitant that places oxidative stress on the cells

37
Q

What tends to precipitate an acute haemolytic episode in G-6-D deficiency?

A

Drugs (anti-malarials, sulphonamides)
Fava beans
Infection

38
Q

What is a specific diagnostic test of G-6-D deficiency?

A

Beutler fluorescent spot test - measures G6D content of cells
Should only be done when patient is not having an acute exacerbation

39
Q

What is the problem in sickle cell disease?

A

Point mutation in sixth codon of the beta haemoglobin chain

40
Q

What potential genotypes might be inherited for sickle cell?

A

Sickle cell disease/homozygous: HbSS

Sickle cell trait/heterozygous: HbAS

41
Q

How does the genetic mutation in sickle cell disease cause illness?

A

Abnormal haemoglobin produced: HbS
This is insoluble at low oxygen tensions
The cells are rigid and inflexible

42
Q

What problems do sickle cells cause?

A

Cause local hypoxia by blocking off blood vessels as they are very rigid - may lead to both acute and chronic problems with organs
Shortened survival of cells - often destroyed by macrophages causing chronic haemolysis

43
Q

What are the three precipitants to creation of sickle cells?

A

Infection
Dehydration
Hypoxia

44
Q

Why are gall stones a feature of sickle cell disease?

A

Large levels of unconjugated bilirubin collect in the gall bladder

45
Q

What are some of the vaso-occlusive crises caused by sickle cell disease?

A 
Osteomyelitis and bone pain
Dactylitis (in kids)
Priapism
Lower limb ulceration
Retinopathy
Tubular interstitial nephritis
46
Q

What bacteria is associated with osteomyeltitis in sickle cell disease?

A

Salmonella

47
Q

What are the life threatening complications of sickle cell disease?

A

Pulmonary syndrome (due to infection, fat embolism and sickle cell sequestration) can lead to pulmonary hypertension long-term
Stroke
Cardiac problems

48
Q

How is sickle cell diagnosed?

A

Haemoglobin electrophoresis - will see HbS

Sickle cell solubility

49
Q

What are the two main types of autoimmune haemolytic anaemia?

A

Warm

Cold

50
Q

What is warm autoimmune haemolytic anaemia?

A

IgG mediated, occuring at temperatures of 37 degrees

51
Q

What is cold autoimmune haemolytic anaemia?

A

IgM mediated, occuring at temperatures

52
Q

What are the causes of warm autoimmune haemolytic anaemia?

A

Idiopathic
Autoimmune disorders (SLE)
Myeloproliferation (CLL/lymphoma)
Drugs

53
Q

What are the causes of cold autoimmune haemolytic anaemia?

A

Infections (EBV, mycoplasma)

Lymphoma

54
Q

How is autoimmune haemolytic anaemia treated?

A

Steroids to induce remission

Immunosuppressants if relapse

55
Q

What are the causes of traumatic or mechanical haemolytic anaemias?

A

Microangiopathic haemolytic anaemia e.g. disseminated intravascular coagulopathy, haemolytic uraemic syndrome and thrombotic thrombocytopaenic purpura
Artificial heart valves
March haemoglobulinuria
Burns

56
Q

How does microangiopathic haemolytic anaemia cause mechanical haemolysis?

A

Abnormal products of coagulation deposited in vessels leads to mechanical damage of red cells

57
Q

What is the characteristic appearance of mechanical haemolytic anaemia on blood film?

A

Schistocytes

58
Q

What is paroxysmal nocturnal haemoglobinuria?

A

An acquired mutation resulting in a red cell defect that disrupts the ability of the cell to make surface anchor proteins
It also affects other cells

59
Q

What is the triad of paroxysmal nocturnal haemoglobinuria?

A

Intravascular haemolysis
Venous thrombosis
Haemoglobinuria (night/morning)`

60
Q

A 24-year old male with longstanding sickle cell disease presents with fatigue, pallor and breathlessness. Investigations reveal: Hb = 4.7 g/dl with a reduced reticulocyte count. What is the most likely cause for this anaemia?

A

Parvovirus
A low reticulocyte count and a low haemoglobin suggest marrow aplasia
This is commonly seen in patients with sickle cell disease and parvovirus infection

61
Q

What is the diagnostic test for spherocytosis?

A

osmotic fragility test

62
Q

Is autoimmune haemolytic anaemia extravascular or intravascular?

A

Both, but occurs predominantly in the spleen

63
Q

What test will be positive in autoimmune haemolytic anaemias?

A

Coombs test

64
Q

What three drugs are most likely to cause warm autoimmune haemolytic anaemia?

A

Penicillins
Methyldopa
Quinine

Haematology (9 decks)

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