Haematology Flashcards
Define thrombocytopenia
plt <150x19^9/L
some say <100
Prevalence of thrombocytopenia in pregnancy?
10%
Classifications of conditions causing thrombocytopenia in pregnancy?
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.
why does gestational thrombocytopenia occur?
does it affect neonate?
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
When does ITP occur?
most common cause in 1st and 2nd trimester
2/3 cases present prior to pregnancy
Cause ITP
autoantibodies towards platelet glycoproteins leading to increased destruction
can ITP autoantibodies cross placenta?
Yes- IgG
How do you diagnose ITP?
very low plt <100
difficult to test for IgG
diagnosis of exclusion
other autoimmune diseases common
What is associated with maternal bleeding and neonatal effect? Gest thrombocytopenia or ITP?
ITP
Serum signs of haemolysis?
schistocytes
LDH >600
bilirubin >20
reduced haptoglobin
How is AFLP different from PET/HELLP?
no thrombocytopenia
Thrombotic microangiopathic anaemia:
When is TTP/HUS and aHUS most common?
most common late pregnancy or PP. Worsening biochemistry 3 days post delivery is suggestive.
Difference between pathology of typical HUS, atypical HUS and TTP?
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.
Treatment of tHUS, aHUS, TTP?
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.
Diagnostic criteria of TMA’s:
- thrombocytopenia; AND
- microangiopathic haemolysis (schistocytes, elevated LDH, haptoglobin decreased, haemoglobin decrease)
plus one or more:
- neurological symptoms,
- renal impairment (usually more HUS),
- GI symptoms.
“FAT RN= fever (tHUS), anaemia, thrombocytopenia, renal failure (HUS), neurological dysfunction (TTP)
evaluate ADAMST13 activity and Shiga toxin/EHEC
Important history and exam of thrombocytopenia?
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
Important results for thrombocytopenia?
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
When should treatment be started for thrombocytopenia?
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
When would LMWH or aspirin be contraindicated in pregnancy?
plt <50
Neonatal management in maternal ITP?
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
Risk of neonatal thrombocytopenia with maternal ITP?
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.
Why does fetal/neonatal alloimmune thrombocytopenia occur?
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.
HPA subtypes of mum + baby in fetal alloimmune thrombocytopenia
mum usually HPA-1a negative
baby HPA-1a positive
prevalence of fetal alloimmune thrombocytopenia? complications?
1:2000-3000 25% will have plt <25 most common cause of low plt in neonate 80% ICH occur during pregnancy high recurrence rate
differentials for neonatal thrombocytopenia?
fetal- alloimmune, CMV, toxo, aneuploidy, autoimmune (ITP/SLE)
neonatal <72hr- placental insufficiency, asphyxia, infection, DIC, alloimmune, autoimmune
neonatal >72hrs = sepsis, NEC
Management of FNAIT?
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).
