Obstetric Haematology

Question 1

What are haemoglobinopathies and name the types

Answer 1

-Autosomal recessive
-Change in globin genes or their expression leading to disease
-Structural: Hb C,D,E, S(sickle), single base substitution in gene leading to altered structure/function
-Thalassaemias: α or β change in expression= reduced rate of synthesis of normal chains
Free chains damage red cell membrane

Question 2

What happens in physiological anaemia and macrocytosis?

Answer 2

• Macrocytosis= enlarged red blood cells
• Plasma vol expands in pregnancy
• Red cell mass expands
• Haemodilution occurs
• Iron deficiency most common anaemia
• MCV increases

Question 3

Why does MCV increase in pregnancy?

Answer 3

Pregnancy increases requirement for iron and results in mobilisation of iron stores and increase in folic acid requirement

Question 4

What is leukocytosis?

Answer 4

• Increase in the number of white cells in the blood

- Neutrophilia in 2/3 trimester

Question 5

Describe gestational thrombocytopenia

Answer 5

• Platelet count falls after 20 weeks
• Most marked in late pregnancy
• Recovers rapidly after delivery

Question 6

Causes of thrombocytopenia in pregnancy?

Answer 6

• Either pregnancy or coincidental
• P production failure: Severe folate deficiency
• P consumptive: Pre-eclampsia, HELLP, DIC
• C production failure: bone marrow infiltration
• C consumptive: sepsis, type 2 vWB, congenital, hypersplenism

Question 7

In terms of coagulation what state is pregnancy? Provide evidence

Answer 7

-Prothrombotic state: platelet activation, reduced fibrinolysis & natural anticoag, inc in procoag factors & markers of thrombin generation,

Question 8

In terms of genetics how does sickle cell disease occur?

Answer 8

Valine substituted for glutamine at position 6 of β-globin gene

Question 9

How are sickle red blood cells formed?

Answer 9

Hb-S polymerises at low O2 tensions to form long fibrils (tactoids) which distort red cell membranes. Cells have short lifespan in blood= haemolytic anaemia

Question 10

What is haemolysis associated haemostatic activation?

Answer 10

• Intravascular haemolysis releases Hb into plasma generates reactive O2 species
• Arginase 1 released metabolising arginine impairing NO homeostasis
• NO decreases leading to activation of platelets & tissue factor

Question 11

What are acute & chronic complications of sickle cell disease?

Answer 11

A= septicaemia, aplastic crisis, vaso-occlusion crisis, sequestration crisis (liver & spleen), abdo & chest pain
C= Hyposplenism (atrophy & infarction), renal disease (medullary infarct w/papillary necrosis), can't concentrate urine, avascular necrosis, leg ulcers, retinopathy, gall stones, osteomyelitis

Question 12

What types of thalassaemia are there? How are they caused?

Answer 12

-β major, intermedia, minor & α
-A= Gene deletions
B=Point mutations

Question 13

Describe the types of β-thalassaemia

Answer 13

Reduced rate of production of β-globin chains caused by excessive α chains
Major: Very severe anaemia in 1-2 year olds, blood film= lots of nucleated RBCs, short stature & distorted limb growth- premature closure of epiphyses, enlarged & overactive spleen & liver, ineffective erythropoiesis- anaemia
Intermedia: Extramedullary haematopoiesis, endocrine & fertility problems
Minor: Blood film resembles iron deficiency, total Hb normal

Question 14

What facial features are seen in thalassaemia patients?

Answer 14

• Abnormal dentition
• Maxillary hypertrophy
• Frontal bossing due to expanded bone marrow
• ‘Hairy’ skull on X-ray due to widening of diploic cavities by marrow expansion

Question 15

How is β thalassaemia major treated?

Answer 15

Iron chelation therapy to prevent death from iron overload

Question 16

What thalassaemia can cause hydrops fetalis?

Answer 16

Hb-Barts is a condition which causes a complete lack of a-globin chain production and is incompatible with life.