A rare case of prolonged fetal and neonatal alloimmune thrombocytopenia (FNAIT) caused by three different antibody types was recently published in the International Journal of Hematology.
Over 80% of FNAIT cases are a consequence of maternal antibodies targeting human platelet antigen 1a (HPA-1a). These antibodies are present in less than 1% of pregnant women. HLA antibodies, on the other hand, are present in over 40% of pregnancies. Whether HLA antibodies are capable of causing FNAIT is a highly debated subject in the medical community, and study results on the topic have been inconclusive.
Due to the rarity of FNAIT due to antibodies different from anti-HPA-1a, the authors stated the case was caused by three different antibodies: -HLA-A11, -B3901 and -Cw7.
Learn more about FNAIT causes and risk factors
Diagnosis and treatment
The case involved a 21-year-old woman in her second pregnancy with a past medical history remarkable for unspecified thrombocytopenia (low platelet count) during childhood. Her pregnancy was uncomplicated, however, her baby presented with elevated bilirubin values (hyperbilirubinemia) after birth, which was resolved with phototherapy.
Eight days after discharge, the baby was diagnosed with thrombocytopenia after a routine laboratory workup for his previous hyperbilirubinemia and one day later he was transferred to a specialized center due to computed tomography (CT) findings suggestive of cerebral hemorrhage.
A repeat CT ruled out a cerebral hemorrhage, but a laboratory workup confirmed the presence of thrombocytopenia. The patient underwent several platelet transfusions without improvement, which prompted physicians to administer treatment with intravenous immunoglobulin (IVIG).
IVIG therapy led to symptom improvement, and the patient was released two weeks later and presented no recurrences.
Starting on the ninth day of admission, physicians performed several tests on the mother to rule out antibody-mediated thrombocytopenia. Results showed that the mother was positive for Anti-HLA-A11, -B3901, and -Cw7 antibodies, but not anti-HPA antibodies.
“Although the role of anti-HLA antibodies in FNAIT remains controversial, a high HLA antibody titer can lead to severe thrombocytopenia,” the authors concluded
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