Alloimmune Thrombocytopenia
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Transcript of Alloimmune Thrombocytopenia
ALLOIMMUNE THROMBOCYTOPENIA
Michael F. McNamara, DO
Sanford Maternal Fetal Medicine
No disclosures
Platelet Disorders in Pregnancy
Gestational thrombocytopenia Idiopathic thrombocytopenia (ITP) Thrombotic thrombocytopenia (TTP) Alloimmune thrombocytopenia (NAIT)
Gestational Thrombocytopenia
Dilution effect Increase of platelet destruction No therapy needed
Idiopathic Thrombocytopenia
1-3 / 1000 pregnancies Pregnancy not usually altering disease
course Therapy
SteroidsIVIGSplenectomy
Thrombotic ThrombocytopeniaPurpura (TTP)
TTP/HUS, may be confused with pre eclampsia
Microangiopathic hemolytic anemia Thrombocytopenia Neurologic changes (headache, lethargy) Thrombotic occlusions in multiple small
vessels Therapy plasma exchange, platelet
transfusions
Alloimmune Thrombocytopenia
Also known as Neonatal Alloimmune Thrombocytopenia (NAIT)
0.2 -1 per 1000 deliveries Low fetal platelets due to maternal
antibodies Index case usually affected Antenatal diagnosis often by ultrasound
with findings of intracranial hemorrhage
Case Study
25 year old female Gravida 5, para 2 Two previous term vaginal deliveries Petechiae, bruising, platelets < 10,000 Counseled on further pregnancies, need
of treatment
Case Study
Presented at 14 weeks gestation Genetic counseling, history reviewed Same paternity as previous infants Father of baby not available for testing
(zygosity)
Case Study
Diagnostic testing (platelet antigen) Maternal
Blood HPA 1b/1b Fetal
Amniotic fluid HPA 1a/1b
Case Study
Preventative therapy IVIG 1 gram / kg weekly Prednisone 1mg /kg daily
Case Study
Antenatal Course Gestational diabetes Severe headaches with IVIG therapy Elevated liver enzymes due to percocet
use secondary to headaches
Case Study
Antenatal steroids at 33 weeks gestation Elected cesarean for delivery with tubal
ligation Vaginal delivery if umbilical cord
sampling performed with normal fetal platelet count
Delivery at 37 weeks, uncomplicated Female infant 5 lbs, 4 oz
Alloimmune thrombocytopenia
Also know as Neonatal Alloimmune throbocytopenia (NAIT)
Incidence 0.2 -1 per 1000 Caucasian births
Maternal antigens against fetal platelets
NAIT
Platelet antigens classified at HPA 1a (PLA1) and HPA 1b (PLA2)
97% adults phenotype HPA 1a (positive for 1a)
69% adults homozygous HPA 1a (1a/1a) 28 % adults heterozygous HPA 1a
(1a/1b) 3 % adults homozygous HPA 1b (1b/1b)
NAIT
Affected pregnancies Most serious complication Intracranial hemorrhage 10-20 % of
cases 25-50 % cases diagnosed prenatally Ultrasound findings of intracranial
hematoma, porencephalic cysts
Antepartum Preventive Therapy
Extremely High Risk Previous baby ICH in second trimester
High riskPrevious baby ICH in third trimester
Moderate riskPrevious baby with thrombocytopenia but no
ICH
NAIT
Recurrence risk up to 100% Thrombocytopenia is severe and
happens earlier in subsequent pregnancies
Previous ICH is risk factor for severe thrombocytopenia in next pregnancy
Low platelet count goes lower in subsequent pregnancies without treatment in utero
NAIT – antenatal therapy
IVIG – very uncommon for ICH with IVIG treatment (11/411 for 2.7%)
Prednisone (additionally) – no better than IVIG alone
Umbilical cord sampling – procedure / bleeding risk
Platelet transfusions – unknown efficacy
IVIG Mechanism of Action
Provision of missing immunoglobulins or neutralizing antibodies, restoration of immune function, and/or suppression of inflammatory and immune-mediated processes
Increase the effect of regulatory T cells, contributing to the maintenance of immunologic self-tolerance
Prevention of reticuloendothelial uptake of autoantibody-coated blood cells (eg, platelets, red cells) through blockade of macrophage Fc-receptors
Case Study #2
Preconception Counseling Gravida 3, Para 3 with recent neonatal
demise from ICH delivered at 38 weeks Low platelet count Paternal 1a/1b Maternal 1b/1b
Case Study #2
Pregnancy #4, amniocentesis Fetus - male1b/1b, normal pregnancy Pregnancy #5, amniocentesis Fetus – male,1a/1b, affected IVIG, prednisone, cord sampling Cesarean at 37 weeks gestation
Case Study #2
First two pregnancies vaginal deliveries with no complications
Oldest is a male, second oldest female Recent testing of the female (now an
adult), 1b/1b
Case Study #2
Platelet antigens classified at HPA 1a (PLA1) and HPA 1b (PLA2)
97% adults phenotype HPA 1a (positive for 1a)
69% adults homozygous HPA 1a (1a/1a) 28 % adults heterozygous HPA 1a
(1a/1b) 3 % adults homozygous HPA 1b (1b/1b) 83% chance of having a baby with 1a/1b
Summary
NAIT cause of neonatal thrombocytopenia
Index case possibly severe problems such as ICH
Decrease complications with in utero therapy, IVIG, prednisone