PB0245 - Series Review of Fetal/neonatal Alloimmune Thrombocytopenia Diagnosis, Management and Outcome in a Tertiary Care Centre

Sunday, July 10, 2022

6:30 PM – 7:30 PM

Location: Exhibition

Presentation Format: In-Person

Presenting Author(s)

Cláudia Santos, PhD, MD

Resident doctor
Immunohemotherapy Department, Centro Hospitalar Universitário de São João, Porto, Portugal
Porto, Porto, Portugal

Co-Author(s)

LC

Lídia Costa

MD
Immunohemotherapy Department, Centro Hospitalar Universitário de São João, Porto, Portugal
Porto, Porto, Portugal
DC

Diana Carneiro Leão

Resident doctor
Immunohemotherapy Department, Centro Hospitalar Universitário de São João
Porto, Porto, Portugal
OG

Oliveira Graça

Medical
Center of Thrombosis and Haemostasis, Department of imunohemotherapy, Centro Hospital e Universitário São João
Porto, Porto, Portugal
FM

Fátima Monteiro

technician
Center of Thrombosis and Haemostasis, Department of imunohemotherapy, Centro Hospital e Universitário São João
Porto, Portalegre, Portugal
FC

Fátima Correia

Medical
Center of Thrombosis and Haemostasis, Department of imunohemotherapy, Centro Hospital e Universitário São João
Porto, Porto, Portugal
CK

Carmo Koch

MD
Immunohemotherapy Department, Centro Hospitalar Universitário de São João, Porto, Portugal
Porto, Porto, Portugal

Background: Fetal/neonatal alloimmune thrombocytopenia (FNAIT) is due to passively acquired maternal antibodies directed against paternal human platelet antigens (HPA) inherited by the newborn, affecting 1:1000 neonates. Intracranial haemorrhage is a major concern (1:10.000 neonates).
In Caucasians, alloimmunization to HPA-1a is involved in 85% of FNAIT. Other antibodies against HPA are rare and its frequencies varies in different ethnic populations.

Aims: Our aim was to diagnose neonatal alloimmune thrombocytopenia and evaluate treatment options and outcomes.

Methods: FNAIT was suspected in 12 cases of fetal intracranial hemorrhage, and/or neonatal nadir platelet count < 100.000/µL at birth or within seven days after birth. Antibodies against platelet in maternal serum/plasma were screened. Genetic polymorphisms for HPA-1,-2,-3,-5 were studied using in house real-time PCR. Maternal thrombocytopenia was excluded in all cases. Therapeutic interventions and outcomes were also evaluated.

Results: Our results confirmed FNAIT in 5/12 of suspected cases. Results are depicted in Table 1. As expected, the majority were due to anti-HPA-1a (n=3), one of which presented both anti-HPA-1a and anti-HPA-2b. We found two cases of rare antigen discrepancies: anti-HPA-1b (n=1) and anti-HPA-2b (n=1). The HPA-2b discrepancy was found in an African-descendent family. Neonates were treated with human immunoglobulin and random donor platelets transfusions when needed (Table 1). All of them had favorable outcomes.

Conclusion(s): FNAIT is an infrequent entity, probably underdiagnosed. Despite its small size, this series highlights the relevance of a prompt diagnosis and intervention. Correct diagnosis impacts the subsequent couples’ offspring as it allows an adequate future pregnancy planning.