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Clinical Pathology > 39 - Obstetric Haemoglobinopathy > Flashcards

39 - Obstetric Haemoglobinopathy Flashcards

1
Q

Haemoglobinopathies

A

Structural Hb Variants

Thalassaemias (alpha or beta)

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2
Q

Structural Hb Variants

A

Hb S, C, D, E

Single base sub in globin gene -> altered structure/function

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3
Q

Thalassaemias

A

Change in globin gene expression leads to reduced rate of synthesis of normal globin chains

Imbalance of alpha and beta chain production

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4
Q

Anaemia in pregnancy

A

Plasma volume expands in pregnancy by 50%

Red cell mass expands by 25%

Haemodilation occurs - max at 32 weeks

MCV increases physiologically in pregnancy

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5
Q

What affect does MCV increase have in pregnant women?

A

Increases iron requirements
Results in mobilisation of Fe stores
Increases folic acid requirements

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6
Q

Another physiological change in blood in pregnancy

A

Leukocytosis

Peaks in 2nd and 3rd trimester

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7
Q

Gestational thrombocytopenia

A

Platelet count usually >70x10^9/l
Platelet count falls after 20 weeks and thrombocytopenia is most marked in late pregnancy
No clinical significance
Recovers rapidly

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8
Q

Causes of thrombocytopenia in pregnancy

A

Pregnancy related = production failure (folate), consumptive

Coincidental = production failure, consumptive (sepsis, viral, type 2B vWD), congenital

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9
Q

Pro-thrombotic state in pregnancy physiological explanation

A 
Platelet activation
Increase in procoagulant factors
Reduction in natural anticoagulants
Reduction in fibrinolysis
Rise in markers of thrombin generation
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10
Q

Diagnosis of haemoglobinopathies

A

Structural Hb variants detected via Hb electrophoresis

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11
Q

Results of Hb electrophoresis

A

Thalassaemias have normal Hb electrophoresis

Small pale red cells resemble iron deficiency

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12
Q

Heterozygous sickle cell anaemia - Investigation results

A

Normal blood film
Hb-S 45%
Hb-A 55%

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13
Q

Heterozygous sickle cell anaemia - clinical presentation

A

No problems except when extreme hypoxia/dehydration

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14
Q

Homozygous sickle cell anaemia - investigation results

A

Anaemia - Hb 6-8g/dl
Blood film shows sickle cells
Hb-S >95% Hb electro

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15
Q

Sickle cell anaemia - acute complications

A

Vaso-occlusive crisis - dactylitis, chest syndrome, ab (mesenteric) pain, long bone, ribs, spinal pain, priapism

Septicaemia
Aplastic crisis
Sequestration crisis

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16
Q

Sickle cell anaemia - chronic complications

A

Hyposplenism - due to infarction and atrophy of spleen
Renal disease - medullary infarction w/ papillary necrosis. Tubular necrosis (bed-wetting at night). Glomerular = chronic renal failure

Avascular necrosis - femoral/humeral heads

Leg ulcers, osteomyelitis, gall stones, retinopathy, cardiac, respiratory

17
Q

Sickle cell anaemia - treatment

A

Penicillin from 6 months (neonatal screening)

Acute crisis managed via analgesia (opiates), hydration, treatment to precipitants

Priapism = w/ education. Acute = intracorporeal phenylephrine
Recurrent = etilefrine
18
Q

a-thalassaemia

A

Most serious - SE Asia + Mediterranean

Both Hb A and F have a-chains

Hb Barts (inheritance of a^0) = hydrops fetalis

Hb H disease
a-trait

19
Q

B-thalassaemia

A

Reduced rate of production of beta-globin chains due to excess alpha chains

Carriers have minor disease

Homozygotes have severe which is usually fatal if untreated - produce little, if any, Hb-A and die of severe anaemia

20
Q

B-thalassaemia minor - blood film resulta

A

Resembles iron deficiency - small, pale red cells

21
Q

Thalassaemia intermedia - clinical features

A

no absolute requirement for regular transfusions to survive 3-5 years of life

Clinical and genetic picture highly variable

All should be genotyped

22
Q

Thalassaemia intermedia - clinical presentation

A 
Pulm. hypertension - ECHO
Extramedullary haematopoiesis
Bone changes and osteoporosis - DEXA
Diabetes mellitis + hypothyroid
Leg ulcers
23
Q

B-thalassaemia major - clinical presentation

A

Severe anaemia at 1to2 years of ages

Abnormal blood film of nucleated RBCs

This due to bone marrow trying to make more red cells to compensate

24
Q

B-thalassaemia major - pathology

A

Alpha chain excess
Increased marrow activity
Enlarged and overactive spleen

25
Q

Alpha chain excess causes…

A 
Ineffective erythropoiesis (red cells die in marrow)
Short RBC lifespan

Which equals anaemia

26
Q

Increased marrow activity…

A

Skeletal deformity, stunted growth
Increased iron absorption and organ damage
Protein malnutrition

27
Q

Enlarged and overactive spleen…

A

Pooling of RBCs

Increased transfusion req.

28
Q

Thalassaemic facies

A

Maxillary hypertrophy
Abnormal dentition
Frontal bossing due to expanded bone marrow

X-ray shows hair on end skull due to widening of diploic cavities by boe marrow expansion(can see hair follicles on X-ray)

29
Q

B-thalassaemia major - treatment

A

Maintain mean Hb 12g/dl
Suppress marrow red cell production and prevent skeletal deformity and liver/splenic enlargement
3 to 4 weekly transfusion from 1st year of life

30
Q

B-thalassaemia major - problems with transfusion treatment

A

Body has no excretory mechanism for iron

By 10-12 years severe iron overload

Gonads/hypothalamus - failure of puberty, growth failure
Pancreas - diabetes
Heart - dilated cardiomyopathy and heart failure
Liver- cirrhosis

31
Q

How much iron is in one blood unit?

A

200mg iron

32
Q

Other complications of transfusions

A

Transmission of infection

Allo-immunisation

33
Q

B-thalassaemia major - treatment

A

Iron chelation therapy to promote excretion of iron in urine and faeces

Desferrioxamine is given 8-12 hourly subcut infusion via syringe pump as home treatment at least 5 nights a week

New oral iron chelators

34
Q

Monitoring chelation - what tests

A

Ferratin
Liver biopsy
MRI (T2)

Clinical Pathology (65 decks)

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