Fetal and neonatal alloimmune thrombocytopenia

Other Names: NAIT Fetal and neonatal alloimmune thrombocytopenia (NAIT) is a blood disorder that affects pregnant women and their babies.

Epidemiology

NAIT was first reported in the literature in 1953 and is estimated to occur in as many as 1 in 1200 live births.

Cause

NAIT results in the destruction of platelets in the fetus or infant due to a mismatch between the mother’s platelets and those of the baby. Certain molecules (antigens) on the surface of the baby's platelets are recognized as foreign by the mother's immune system. The mother’s immune system then creates antibodies that attack and destroy the baby’s platelets.

Though NAIT can occur whenever the mother’s blood mixes with that of the baby, it is usually triggered when the mother is exposed to the baby’s blood during delivery. Many cases of NAIT are mild

Signs and symptoms

Some cases of NAIT are mild. The most common sign is bleeding into the skin which may present as petechiae or localized swellings (hematomas). In more severe cases, the infant may experience bleeding episodes affecting the brain or major organs. These bleeding episodes can be life-threatening. For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed.

100% of people have these symptoms

• Neonatal alloimmune thrombocytopenia

30%-79% of people have these symptoms

• Cephalohematoma
• Petechiae
• Spontaneous hematomas

5%-29% of people have these symptoms

• Ecchymosis
• Hematuria(Blood in urine)
• Melena

1%-4% of people have these symptoms

• Bilateral sensorineural hearing impairment
• Blindness
• Cerebral palsy
• Global developmental delay
• Subarachnoid hemorrhage

Diagnosis

Doctors may consider a diagnosis of NAIT if they notice bleeding or bruising in a baby, or low platelet counts on a blood test after birth, or neurologic symptoms. Some babies may have a specific pinpoint rash called “petechiae”. If a diagnosis of NAIT is suspected, then the baby should be treated as if it had NAIT until the diagnosis is confirmed. The diagnosis is confirmed by taking blood samples from the baby's parents, and sometimes the baby. Maternal and paternal platelet antigen phenotyping and screening of the maternal serum for anti-platelet antibodies can be performed.

Additionally, platelet antigen genotyping can be performed on the maternal and paternal blood to determine the exact nature of the incompatibility. Neonatal platelet counts on laboratory testing are typically under 20,000 μL−1. Higher counts may suggest a different diagnosis, such as maternal immune thrombocytopenic purpura.

Even in mildly affected babies it is important to fully investigate and diagnose the baby because the results can be critical for effective management of any future pregnancies.

Treatment

Management for pregnancies determined to be at risk remains controversial but may include a planned delivery and maternal avoidance of nonsteroidal anti-inflammatory drugs (NSAIDS) and aspirin during pregnancy.

Management strategies have also included maternal intravenous immunoglobulin (IVIG) or maternal steroids and more invasive procedures such as fetal blood sampling and fetal platelet transfusions. The less invasive approach is currently favored.

Management of the affected infant after birth depends on the specific signs and symptoms but may include periodic ultrasounds of the brain to check for bleeding, platelet transfusion, and IVIG. In the absence of intracranial bleeding, the prognosis is generally favorable and the platelet count usually improves within 8 to 10 days.

NIH genetic and rare disease info

• NIH info on Fetal and neonatal alloimmune thrombocytopenia

Fetal and neonatal alloimmune thrombocytopenia is a rare disease.

Fetal and neonatal alloimmune thrombocytopenia Resources
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