It is recommended that human platelet antigen (HPA) genotyping be performed in all newborns with severe thrombocytopenia—that is, abnormally low platelet levels—in order to rule out fetal and neonatal alloimmune thrombocytopenia (FNAIT), according to findings from a case study recently published in the Asian Journal of Transfusion Science.
Among neonates, it is well recognized that FNAIT is a leading cause of severe thrombocytopenia. Although thrombocytopenia also can be associated with hemolytic disease of the fetus and newborn (HDFN), the presentation in this disorder is typically of mild to moderate severity.
The case described involved a 34-year-old female in India. She had experienced six pregnancies, given birth to a viable child four times and currently has one living child.
The pregnant patient presented to the hospital in Rajasthan, India, at 31 weeks, two days gestational age. A cesarean section was scheduled based on the presence of fetal hydrops. Her blood type was O Rhesus (Rh)-negative. Results of an indirect antiglobulin test indicated that the mother’s blood likely contained a high level of antibodies.
Read more about FNAIT causes and risk factors
She underwent antibody screening, which revealed the presence of anti-D, anti-C, anti-E and anti-Jka antibodies. The mother was a recognized case of Rh isoimmunization with unknown anti-D status and a poor obstetric history. Her first three pregnancies resulted in full-term intrauterine deaths, her fourth pregnancy was associated with a full-term female child, and her fifth pregnancy led to a spontaneous abortion at 10 weeks.
In this current pregnancy, the patient underwent two sessions of plasma exchange, which led to a decrease in her anti-D titers. She received seven intrauterine transfusions (IUTs) as well, with her initial IUT at 18 weeks’ GA and the last IUT on the day prior to hospital admission. The fetus’s blood type was O RhD-positive.
The mother delivered a preterm female baby who weighed 3.86 lb. The infant’s hemoglobin level was 11.8 g/dL, her platelet count was 12 g/L, and her bilirubin level was 138.5 mmol/L.
How HPA genotyping could have led to earlier diagnosis
The baby ultimately underwent double-surface phototherapy and a single exchange transfusion with phenotype-matched packed red blood cells (PRBCs), which was associated with lowering her bilirubin concentration to less than 100 mmol/L. Based on ultrasonography findings, there were no signs of intracerebral or intraventricular hemorrhages in the infant’s cranium.
In this case study, the presence of severe thrombocytopenia along with bleeding manifestations in the baby led to a provisional diagnosis of FNAIT. Platelet cross-matching in the father, maternal siblings, and group-specific random donors were all incompatible.
HPA genotyping was performed of the newborn, the mother and the father. In the ensuing 10 days, the baby received transfusions with 11 units of random donor platelets, one unit of PRBCs, and three doses of intravenous immunoglobulin.
After 10 days, the baby’s platelet counts began to increase. Results of HPA genotyping revealed that there was no HPA antigen incompatibility among the baby, the mother or the father. After other causes were excluded, it was concluded that the very severe thrombocytopenia reported in the newborn was likely due to HDFN.
“HDFN can rarely cause severe thrombocytopenia,” the authors noted. “However, when a newborn presents with severe/very severe thrombocytopenia, [FNAIT] is to be ruled out with HPA genotyping, even in resource-limited settings, to plan out subsequent pregnancies,” they concluded.
