Summary about Disease
Neonatal Alloimmune Thrombocytopenia (NAIT) is a condition where a mother's immune system attacks the platelets of her fetus. This happens when the fetus inherits a platelet antigen from the father that the mother lacks. The mother develops antibodies against this antigen, and these antibodies cross the placenta, attacking the fetal platelets and leading to thrombocytopenia (low platelet count) in the newborn. NAIT can range from mild to severe, with the most serious complication being intracranial hemorrhage (bleeding in the brain).
Symptoms
The most common symptom is petechiae (small, pinpoint red or purple spots on the skin) and purpura (larger areas of bruising). Other symptoms can include:
Bleeding from the nose (epistaxis)
Bleeding from the gums
Blood in the stool (melena) or urine (hematuria)
Intracranial hemorrhage (ICH), which can lead to seizures, neurological damage, or death.
Rarely, anemia due to bleeding.
Causes
NAIT is caused by alloimmunization, where the mother develops antibodies against fetal platelet antigens she lacks. This occurs when the fetus inherits a platelet antigen from the father that the mother does not possess. The most common antigen involved is human platelet antigen-1a (HPA-1a), also known as PLA1. Maternal antibodies (IgG) cross the placenta and destroy the fetal platelets.
Medicine Used
Intravenous Immunoglobulin (IVIG): This is the primary treatment and works by flooding the infant's system with antibodies, preventing the maternal antibodies from attacking the baby's platelets.
Platelet Transfusions: Platelets, preferably HPA-matched platelets from the mother (if available and not carrying the target antigen) or antigen-negative donor platelets, are transfused to raise the platelet count quickly.
Steroids: In some cases, corticosteroids may be used to help reduce the destruction of platelets.
Is Communicable
No, NAIT is not communicable. It is an autoimmune condition arising from a specific genetic incompatibility between mother and fetus regarding platelet antigens, not an infectious disease.
Precautions
For subsequent pregnancies in women who have had a child with NAIT:
Early Detection: Screening for platelet antibodies in the mother is recommended.
IVIG during pregnancy: If antibodies are detected, IVIG infusions can be administered to the mother during pregnancy to prevent or minimize fetal thrombocytopenia.
Fetal platelet count monitoring: Amniocentesis or fetal blood sampling (FBS) was previously used, but is now less common due to risks; non-invasive monitoring using antibody titers and clinical history is preferred.
Delivery method: Cesarean delivery may be considered to reduce the risk of intracranial hemorrhage during birth, especially if fetal platelet counts are low despite treatment.
How long does an outbreak last?
NAIT is not an outbreak. The thrombocytopenia in the newborn typically resolves within days to weeks after birth as the maternal antibodies are cleared from the infant's circulation. The treatment duration depends on the severity of the thrombocytopenia and the response to IVIG and/or platelet transfusions. The disease isn't something that "lasts" as in a chronic illness; it's a transient condition.
How is it diagnosed?
Newborn Platelet Count: A low platelet count in a newborn, especially if there is a history of bleeding or bruising.
Maternal Platelet Antibody Screening: Testing the mother's blood for antibodies against platelet antigens (e.g., HPA-1a).
Paternal Platelet Antigen Typing: Determining the father's platelet antigen type to identify the antigen that the mother lacks and against which she has formed antibodies.
Exclusion of other causes: Ruling out other possible causes of thrombocytopenia in the newborn, such as infections or other immune disorders.
Timeline of Symptoms
Prenatal (if known): No visible symptoms. Only detectable through antibody screening of the mother.
At Birth/Shortly After: Petechiae, purpura, bleeding (e.g., nosebleeds, gum bleeding). Severity varies.
Within First Few Days/Weeks: Potential for intracranial hemorrhage, seizures (if ICH occurs). If left untreated, complications can arise.
Resolution: As maternal antibodies clear, platelet counts rise, and symptoms resolve (with treatment).
Important Considerations
Early diagnosis and treatment are crucial to prevent intracranial hemorrhage and other serious complications.
Subsequent pregnancies require careful management to minimize the risk of NAIT recurrence.
The severity of NAIT can vary significantly from one infant to another.
Parental education and support are important to ensure appropriate care and monitoring of the newborn.
HPA-matched platelets may be difficult to obtain, requiring careful planning and coordination with blood banks.