Haematology

Question 1

Define thrombocytopenia

Answer 1

plt <150x19^9/L

some say <100

Question 2

Prevalence of thrombocytopenia in pregnancy?

Answer 2

10%

Question 3

Classifications of conditions causing thrombocytopenia in pregnancy?

Answer 3

pregnancy: gestational (75%), HELLP, DIC, PET (15%), AFLP

non pregnancy related

immune: ITP, SLE/APLS, TTP/aHUS, HUS

non-immune: infections (HIV, hepatitis, H Pylori), sequestration/hypersplenism, B12/folate deficiency, Type 2B VW disease, congenital thrombocytopenia, bone marrow failure.

Question 4

why does gestational thrombocytopenia occur?

does it affect neonate?

Answer 4

dilutional
placental platelet sequestration

typically recurs each pregnancy
very rare for plt less than 100. Some very rare cases <70
Does not affect neonate
Resolves 2-3 months after delivery

Question 5

When does ITP occur?

Answer 5

most common cause in 1st and 2nd trimester

2/3 cases present prior to pregnancy

Question 6

Cause ITP

Answer 6

autoantibodies towards platelet glycoproteins leading to increased destruction

Question 7

can ITP autoantibodies cross placenta?

Answer 7

Yes- IgG

Question 8

How do you diagnose ITP?

Answer 8

very low plt <100
difficult to test for IgG
diagnosis of exclusion
other autoimmune diseases common

Question 9

What is associated with maternal bleeding and neonatal effect? Gest thrombocytopenia or ITP?

Answer 9

ITP

Question 10

Serum signs of haemolysis?

Answer 10

schistocytes
LDH >600
bilirubin >20
reduced haptoglobin

Question 11

How is AFLP different from PET/HELLP?

Answer 11

no thrombocytopenia

Question 12

Thrombotic microangiopathic anaemia:

When is TTP/HUS and aHUS most common?

Answer 12

most common late pregnancy or PP. Worsening biochemistry 3 days post delivery is suggestive.

Question 13

Difference between pathology of typical HUS, atypical HUS and TTP?

Answer 13

typical HUS= toxin causes endothelial injury, platelet aggregation and red cell shearing (E Coli, shigatoxin)

atypical HUS= complement activation causing endothelial damage and then causing endothelial injury, platelet clumping.

TTP= ADAMST13 protein deficiency. long VWB multimers with platelet fibrils not broken up. Can be acquired (infection/malignancy) or genetic (inherited ADAMST13 deficiency). High risk recurrence future pregnancy. Haematology input future.

Question 14

Treatment of tHUS, aHUS, TTP?

Answer 14

tHUS = supportive treatment. await for trigger to resolve.

aHUS= stop complement pathway. ecaluzimab. Stops C5 in cascade

TTP= get rid of antibody. steroids and plasma exchange.

Question 15

Diagnostic criteria of TMA’s:

Answer 15

1. thrombocytopenia; AND
2. microangiopathic haemolysis (schistocytes, elevated LDH, haptoglobin decreased, haemoglobin decrease)

plus one or more:

1. neurological symptoms,
2. renal impairment (usually more HUS),
3. GI symptoms.

“FAT RN= fever (tHUS), anaemia, thrombocytopenia, renal failure (HUS), neurological dysfunction (TTP)

evaluate ADAMST13 activity and Shiga toxin/EHEC

Question 16

Important history and exam of thrombocytopenia?

Answer 16

history
bleeding/thrombosis
infections
previous abnormal blood results
diet (vegan)
past obstetric/neonatal history
other autoimmune disease (SLE/thyroid)
Fhx of bleeding disorders
Drugs (including complementary)

exam
mouth, mucosa
petechiae
bruising
lymphadenopathy
splenomegaly

Question 17

Important results for thrombocytopenia?

Answer 17

look at blood film + previous investigations

• may be falsely low due to clumping
• LFT/Renal/Thyroid
• Haemolysis screen (reticulocytes, haptoglobin, DAT, LDH)
• viral screen
• H Pylori serology
• VW studies
• ANA
• B2 glycoprotein and anticardiolipin
• platelet aggregometry if suspicious von willebrands

Question 18

When should treatment be started for thrombocytopenia?

Answer 18

don’t often bleed unless plt <20
consider if invasive procedure and <50

may be more at risk if abnormal platelet function and low plt count (i.e. big useless platelets)

Delivery

• > 50 at least
• > 70 for anaesthetics
• tertiary centry
• no FSE/FBS
• no instrumental
• avoid IM if <50

Question 19

When would LMWH or aspirin be contraindicated in pregnancy?

Answer 19

plt <50

Question 20

Neonatal management in maternal ITP?

Answer 20

check cord blood plt count at delivery, check again if low day 2-5.
cranial USS if platelets <50

If ICH –> plt transfusion for plt >100
if bleeding + plt <30 = IVIg + plt. avoid IM injections such as vitamin K until plt count established

Question 21

Risk of neonatal thrombocytopenia with maternal ITP?

Answer 21

5% neonates have plt <20
5% have plt 20-50

more at risk if maternal splenectomy, previous sibling.
even if mum responds to steroids, neonate does not necessarily.

Question 22

Why does fetal/neonatal alloimmune thrombocytopenia occur?

Answer 22

platelets have HPA’s
paternal HPA’s may be incompatible with mum
foetal makes plt from 16 weeks. platelet crosses placenta
mum develops ab to antigen
antibody crosses placenta, destroys fetal platelets.

Question 23

HPA subtypes of mum + baby in fetal alloimmune thrombocytopenia

Answer 23

mum usually HPA-1a negative

baby HPA-1a positive

Question 24

prevalence of fetal alloimmune thrombocytopenia? complications?

Answer 24

1:2000-3000
25% will have plt <25
most common cause of low plt in neonate
80% ICH occur during pregnancy
high recurrence rate

Question 25

differentials for neonatal thrombocytopenia?

Answer 25

fetal- alloimmune, CMV, toxo, aneuploidy, autoimmune (ITP/SLE)

neonatal <72hr- placental insufficiency, asphyxia, infection, DIC, alloimmune, autoimmune

neonatal >72hrs = sepsis, NEC

Question 26

Management of FNAIT?

Answer 26

one Pregnancy FNAIT, no ICH
IVIG from 20 weeks
high dose IVIG + steroids 32/40

one pregnancy FNAIT + ICH >28/40
IVIG 12 weeks
high dose IVIG from +/-20 weeks OR 28 weeks
prednisone from 20 weeks (0.5mg/kg/day)

one pregnancy FNAIT + ICH <28w

• high dose IVIG 12 weeks
• prednisone 1mg/kg/day from 20weeks

Caesarean section to consider (VD high risk period).