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Clinical Pathology > Theme 7 Haematology: Haemaglobinopathies, Obstetric Haematology and paediatric haematology > Flashcards

Theme 7 Haematology: Haemaglobinopathies, Obstetric Haematology and paediatric haematology Flashcards

1
Q

When do you have a haemoglobinopathy screening in pregnancy?

A

around 8 weeks

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2
Q

What testing is carried out if:

  1. In low prevalence area
  2. In high prevalence area
A
  1. family origin and FBC

2. HPLC +/- partner testing

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3
Q

When is a haemoglobinopathy screening carried out post-natally?

A

at 5 days

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4
Q

What is the post natal haemoglobinopathy screening test?

A

heel prick test:

  • analysis of dried blood spot
  • multiple conditions tested for
  • goal is early detection of sickle cell disease
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5
Q

State the haematological changes in pregnancy

A
  • plasma volume expands by 50%
  • red cell mass expands by 25%
  • haemodilution occurs –> this means there is a fall in haemoglobin as the plasma volume expands faster than the red cell mass
  • the MCV increases
  • folic acid requirements increase
  • leukocytosis (mainly a neutrophilia
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6
Q

What is the most common cause of anaemia in pregnancy?

A

iron deficiency

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7
Q

What happens to your platelet count during pregnancy?

A
  • gestational thrombocytopenia

- platelet count drops in some women toward the end of pregnancy

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8
Q

What is the coagulation state in pregnancy?

A
  • pregnancy is a pro-thrombotic state
  • evidence of platelet activation
  • reduction in anticoagulants and fibrinolysis
  • rise in thrombin generation
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9
Q

Which coagulation factors are increased in pregnancy?

A
  • plasma fibrinogen and FVII
  • FV, VIII, X, XII
  • big increase in vWF
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10
Q

erythrocyte production is controlled by what?

A

erythropoietin produced in kidneys

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11
Q

What is the function of the globin chain in haemoglobin

A
  • protects haem from oxidation
  • renders the molecule soluble
  • permits variation in oxygen affinity
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12
Q

Explain the genetic control of an adult globin chain

A
  • alpha chains produced on chromosome 16
  • beta or gamma chains produced on chromosome 11
  • forms Hb-A (adult haemaglobin)
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13
Q

Explain the genetic control of an foetal globin chain

A
  • alpha chains produced on chromosome 16

- delta chains produced on chromosome 11 produce Hb-F

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14
Q

What is a haemaglobinopathy?

A

changes in globin genes or their expression leads to disease

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15
Q

What is a thalassaemia?

A
  • alpha or beta
  • change in globin gene expression leads to reduced rate of synthesis of normal globin chains
  • pathology is due to imbalance of alpha and beta chain production
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16
Q

Explain structural Hb variants

A
  • usually a single base substitution in globin gene
  • altered structure and function
  • HbS (sickle), C, D, E
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17
Q

What is the relationship between worldwide distribution of haemoglobin disorders and falciparum malaria?

A

suspected that the mutations persisted because they offer a survival advantage as the different red cell membrane in haemaglobin disorders results in resistance to malarial attack

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18
Q

How do we diagnose a haemaglobinopathy?

A
  • FBC
  • haemaglobin electrophoresis
  • isoelectric focusing
  • high performance liquid chromatography (HPLC)

specialist tests:

  • heat stability, isopropanol
  • oxygen dissociation curve
  • DNA analysis
  • mass spectrometry
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19
Q

When is the sickle cell trait a problem?

A

extreme hypoxia/ dehydration e.g bad anaesthesia or flying unpressurised military aircraft

20
Q

Why are sickle cells so called?

A

Hb-S polymerises to form long fibrils which distort the red cell membrane and produce the classical sickle shape

21
Q

Why do people with sickle cell disease have haemolytic anaemia?

A

the sickled red cells have a short life span in the blood so it requires a massive increase in red cell turnover to maintain haemoglobin

22
Q

What is haemolytic anaemia?

A

a disorder in which red blood cells are destroyed faster than they are made

23
Q

In sickle cell disease, what will you expect to see on:

  1. Blood count
  2. Blood film
  3. Hb electrophoresis
A
  1. anaemia
  2. visible sickle cells and hyposplenism
  3. Hb-S > 95%, Hb-A 0%
24
Q

How might a patient with sickle cell disease present?

A
  • usually 3-6 months old

- may present with jaundice, physically enlarged spleen until hyposplenism in the first decade

25
Q

What are the acute complications of sickle cell disease?

A
  • vaso-occlusive crisis –> hands and feet pain (dactylitis), chest syndrome, abdominal pain, bone infarction, priapism (painful erection)
  • septicaemia due to underactive spleen
  • aplastic crisis
  • sequestration crisis - rapid pooling of red cells and enlargement of organ
26
Q

What are the chronic complications of sickle cell disease?

A
  • hyposplenism: due to infarction and atrophy of spleen
  • renal disease
  • avascular necrosis
  • chronic renal failure/ dialysis
27
Q

When should you transfuse patients with sickle cell?

A

in acute chest crisis, acute stroke, pre-operative and splenic sequestration

28
Q

What is the main medical therapy for sickle cell?

A

hydroxycarbamide

  • increases % of HbF in blood
  • acts as an anti-inflammatory
29
Q

What are the most common single gene disorders?

A

thalassaemia

30
Q

What are the different types of thalassaemias?

A

• Divided into a, B, δβ , and γδβ according to which globin chain is reduced

31
Q

What is the pathology of B-thalassaemia?

A
  • reduced rate of production of beta globin chains

- pathology caused by excess alpha chains

32
Q

What will a blood picture look like from a patient with B-thalassaemia?

A
  • resembles iron deficiency
  • small, pale red cells
  • MCV reduced
33
Q

What are the medical complications of thalassaemia intermedia?

A
  • pulmonary hypertension
  • extra medullary haematopoiesis
  • bone changes and osteoporosis
  • endocrine and fertility
  • leg ulcers
34
Q

What are the signs and symptoms of B-thalassaemia major?

A
  • very severe anaemia
  • short stature and distorted limb growth due to premature closure of epiphyses in long bones
  • child will be pale and failure to thrive
  • enlarged liver and spleen
35
Q

Explain the pathology of B-thalassaemia major

A
  • anaemia arises because there is alpha chain excess -this causes ineffective erythropoiesis (red cells die in marrow)
  • so there is a shortened red cell lifespan (haemolysis)
36
Q

What does a thalassaemic face look like?

A
  • maxillary hyperthrophy
  • abnormal dentition
  • frontal bossing due to expanded bone marrow
37
Q

What is an “hair on end” skull

A
  • in X-ray of skull of thalassaemic patients

- due to widening of diploic cavities by marrow expansion

38
Q

Why do we use a transfusion to treat B-thalassaemia major?

A
  • to maintain mean Hb 120g/l

- suppresses marrow red cell production and prevents skeletal deformity and liver/spleen enlargement

39
Q

What are the complications of transfusion?

A
  • transmission of infection
  • iron overload
  • allo-immunisation
  • formation of allo antibodies that make it harder to cross-match blood and infection
40
Q

What is the biggest cause of death in patients with thalassaemia?

A

heart failure

41
Q

How is iron overload prevented in thalassaemic patients?

A
  • iron chelation therapy

- desferrioxamine

42
Q

In antenatal screening for haemoglobin disorders, what are the options if antenatal test is positive?

A
  • pre-implantation diagnostic testing
  • choriovillus biopsy
  • termination
43
Q

How do healthy neonates and children differ haematologically from adults?

A
  • neutrophils are increased in babies
  • eosinophils and basophils do not change much in quantity
  • you have the adequate number of platelets in a baby at 20 weeks
44
Q

When are blood cells first made

A

day 18 in the yolk sac

45
Q

What are the acquired causes of anaemia in childhood?

A
  • physiological
  • infection
  • tumours
  • trauma
  • iatrogenic
  • any systems
46
Q

What is the most common cause of anaemia in children?

A

iron deficiency

Clinical Pathology (57 decks)

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