About Foetal and neonatal alloimmune thrombocytopenia (FNAIT)

About Foetal and neonatal alloimmune thrombocytopenia (FNAIT)

What is FNAIT?

  • FNAIT is a rare condition where a mother’s immune system mistakenly attacks the baby’s platelets, leading to dangerously low platelet levels.
  • Platelets help blood clot, so low levels can increase the risk of internal bleeding and lead to the baby’s body being unable to heal itself properly.
  • Currently, there is no standard blood test during pregnancy to check if an expecting mother has antibodies against platelets.
  • Many do not realise they have this condition until they give birth to a baby with a low platelet count or if a close family member has an affected baby.

It is crucial for those at risk to be aware of this potential issue, as early detection and intervention can significantly improve outcomes for both the mother and their baby. Awareness and education are vital to ensure that more families can receive timely care and support.

  • FNAIT occurs when a baby's platelets are different from their mother’s, and the mother’s immune system sees them as ‘foreign’.
  • The mother’s immune system creates a type of maternal antibody called alloantibodies that cross the placenta and attack the baby's platelets.
  • This can lead to a condition called thrombocytopenia (low platelet count) in the developing baby.
  • This condition puts the baby at risk for serious issues with blood clotting, including life-threatening brain bleeds for the baby before or after birth in severe cases.

  • FNAIT occurs in approximately 1 in 1,000 pregnancies.
  • In most cases, FNAIT is only discovered after the first pregnancy, when the newborn shows signs like low platelet counts, bleeding, bruising, or in severe cases, intracranial haemorrhage (ICH). The risk of FNAIT increases in future pregnancies, making early detection and management crucial for reducing complications.
  • Depending on how many of the baby’s platelets are damaged or destroyed, it could have no impact on them. This could mean symptoms do not manifest until later pregnancies.
  • If a mother’s platelets drop below a certain threshold, FNAIT may be suspected.
  • In mild cases, FNAIT could cause unexplained bruising, especially in areas that do not normally sustain injuries. This can still be alarming to caregivers and healthcare professionals as it may have implications for future pregnancies as well.
  • In more extreme cases, severe bleeding on the brain could lead to developmental issues in the long term, or death.
  • Once platelet alloantibodies are made, they can remain in the mother’s blood for a long time, sometimes for life.
  • Although the presence of these alloantibodies will not harm the mother’s own platelets, they need to be taken into account during future pregnancies as they can still attack the platelets of new developing babies in the womb.

Diagnosing FNAIT

  • Right now, there is no routine test during pregnancy to check for FNAIT.
  • Expecting mothers can be tested for FNAIT based on their previous pregnancies if doctors suspect a risk, particularly if:
    • They have a history of a baby born with low platelet counts for no clear reason.
    • They had a previous baby who showed symptoms of FNAIT at birth like unexplained bleeding, bruising, or in severe cases, bleeding in the brain.
    • Tests unexpectedly revealed the absence of a specific platelet marker in the mother’s blood, which may suggest potential incompatibility with the baby's platelets.
  • Testing for FNAIT is usually conducted at a specialist center by a doctor with expertise in maternal foetal diseases. To diagnose FNAIT, doctors can use:
    • A test to check for antibodies that react with platelets (flow cytometry or cell free DNA testing).
    • A test that finds specific proteins that the antibodies are targeting (modified antigen capture enzyme-linked immunosorbent assay [ELISA MACE]).

If you are concerned about your own status, it is important to discuss your options for diagnostic testing with your healthcare team.

Managing FNAIT

  • Specialist care: As the condition is so rare, diagnostic tests are normally carried out at a specialist centre by a haematologist and foetal medicine doctor who will interpret the results together.
  • Future pregnancies: Proper diagnosis helps doctors manage future pregnancies more effectively. It is important to maintain continued conversations with your healthcare team if FNAIT or low platelet levels are detected.
  • Monitoring and timely intervention: If FNAIT is confirmed, a team of specialists can work together to ensure you and your baby receive the best possible care. Close monitoring is key to your healthcare team providing timely intervention and preventing severe complications.

Useful Resources and Support

NAIT Babies

NAIT Babies is a charitable organisation, based in the UK and run by families who have been diagnosed with FNAIT. The organisation provides support and resources to families affected by the disease, helping them navigate diagnosis, treatment and postnatal care. Through education, advocacy, and community outreach, NAIT Babies aims to improve outcomes for affected infants and their families.

References

Cremers FP et al. Genes. 2018; 9(4):215.
Ziccardi L et al. Int J Mol Sci. 2019; 20(22):5722.
MedlinePlus Genetics. National Institutes of Health. What is a gene? 2021. Available at: https://medlineplus.gov/genetics/understanding/basics/gene. Last accessed: February 2024.
MedlinePlus Genetics. National Institutes of Health. What is DNA? 2021. Available at: https://medlineplus.gov/genetics/understanding/basics/dna. Last accessed: February 2024.
MedlinePlus Genetics. National Institutes of Health. What is a gene variant and how do variants occur? 2021. Available at: https://medlineplus.gov/genetics/understanding/mutationsanddisorders/genemutation. Last accessed: February 2024.
MedlinePlus Genetics. National Institutes of Health. Help me understand genetics: mutations and health. 2018. Available at: https://medlineplus.gov/genetics. Last accessed: February 2024.
Healthline. Eye. 2015. Available at: https://www.healthline.com/human-body-maps/eye#1. Last accessed: February 2024.
MedlinePlus. National Institutes of Health. Retinal disorders. 2021. Available at: https://medlineplus.gov/retinaldisorders.html. Last accessed: February 2024.
Narayan DS et al. Acta Ophthalmologica. 2016; 94(8):748–754.
Lamb TD. Eye (Lond). 2016; 30(2):179–185.
Lam, B.Let al. Orphanet J Rare Dis. 2021;16, 514.
Moore AT. Ophthalmology. 2017; 124(9):1254–1255.
Méjécase C et al. Ther Adv Ophthalmol. 2020; 12:1–128.
Tatour Y et al. Diagnostics (Basel). 2020;10(10):779.
Liu W, et al. Int J Mol Sci. 2022;23(9):4883.
National Institutes of Health. US National Library of Medicine. Leber congenital amaurosis. 2021;1-4. Available at: https://clinicaltrials.gov/ct2/show/NCT02781480. Last accessed: February 2024.
National Institutes of Health. US National Library of Medicine. Stargardt disease. 2020;1-13. Available at: https://clinicaltrials.gov/ct2/results?recrs=&cond=Stargardt+Disease&term=&cntry=&state=&city=&dist=. Last accessed: February 2024.
National Organization for Rare Disorders. Retinitis pigmentosa. Available at: https://rarediseases.org/rare-diseases/retinitis-pigmentosa#:~:text=Retinitis%20pigmentosa%20(RP)%20comprises%20a,the%20inside%20of%20the%20eyes. Last accessed: February 2024.
Wang DY et al. Clin Chim Acta. 2005; 351(1-2):5-16.
Chivers, M et al. ClinicoEconomics and outcomes research: CEOR. 2021; 13:565–572.
Martinez-Fernandez De La Camara C et al. Expert Opinion Orphan Drugs. 2018; 6(3):167-177.
Fuster-Garcia C, et al. Int J Mol Sci. 2021; 22(13):6723.
Piotter E, et al. Biomolecules. 2021;11(8):1179.
Huang D et al. Ophthalmic Genet. 2022; 43(1):1-26.
MedlinePlus. Stargardt macular degeneration. Available at: https://medlineplus.gov/genetics/condition/stargardt-macular-degeneration/#references. Last accessed: February 2024.
Tsang S, et al. Adv Exp Med Biol. 2018; 1085:53-60.
Michalakis Set al. Mol Diagn Ther. 2022; 26(1):51–59.
Huang CH, et al. Genes (Basel). 2021; 12(8):1261.
Kapetanovic JC, et al. Genes (Basel). 2019; 10(10):738.
Forsyth R & Gunay-Aygun M. Gene Reviews. 2003 (updated 2023). University of Washington, Seattle. Available at: https://www.ncbi.nlm.nih.gov/sites/books/NBK1363/. Last accessed: February 2024.
Forsythe E et al. Orphanet J Rar Dis. 2023; 18:181.
Forsythe E et al. Eur J Hum Genet. 2013; 21(1):8-13.
Lee KY et al. Genet Med. 2015; 17(4):245-252.