A recent study published in the journal Blood offers a potential explanation for why some cases of fetal and neonatal alloimmune thrombocytopenia (FNAITFetal and neonatal alloimmune thrombocytopenia A rare condition in which a mother’s immune system attacks fetal platelets, leading to dangerously low platelet levels before and/or after birth.) lead to bleeding in the brain while others do not.
Fetal and neonatal alloimmune thrombocytopeniaFetal and neonatal alloimmune thrombocytopenia A rare condition in which a mother’s immune system attacks fetal platelets, leading to dangerously low platelet levels before and/or after birth. (FNAIT) is a rare condition where a mother’s immune system attacks her baby’s platelets. Its most severe complication is intracranial hemorrhageBrain bleed Bleeding inside the fetal brain, also known as an intracranial hemorrhage. In FNAIT, it's often caused by severe thrombocytopenia and can lead to long-term disability or death. , or bleeding in the brain, which occurs in 7% to 26% of cases and can cause permanent brain damage or death. But simple testing of antibody and platelet levels does not reliably show which babies will suffer a dangerous brain bleedBrain bleed Bleeding inside the fetal brain, also known as an intracranial hemorrhage. In FNAIT, it's often caused by severe thrombocytopenia and can lead to long-term disability or death. , making it hard for doctors to counsel patients.
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In the new study, researchers analyzed blood samples from babies with FNAIT, some of whom had experienced bleeding on the brain. The babies who had bleeding in the brain all had a specific kind of antibody (protein) called anti-αvβ3.
The researchers also found that anti-αvβ3 antibodies effect the cells that line blood vessels, causing damage and making it harder for new, healthy blood vessels to grow properly.
Read more about FNAIT testing and diagnosis
“In conclusion, we find evidence that ICH [intracranial hemorrhage] in FNAIT is based on vascular impairment,” the researchers said, meaning that blood vessel damage could be the reason for bleeding on the brain, and not just low platelet levels, as previously thought.
This study suggests that the usual blood tests for platelet antibodies are not enough to tell which babies are at risk of bleeding in the brain. Adding tests that look for antibodies against blood vessel cells could help doctors sort pregnancies into higher and lower risk for brain bleeding.
In this small study, a mix of lab tests that measured what the antibodies were and how they behaved correctly picked out all six babies who did have brain bleeding and all four who did not, which hints that this approach could become a useful diagnostic tool.
