Neonatal Alloimmune Thrombocytopenia (NAIT)

Presentation

• Unexplained, severe thrombocytopenia (platelets < 50,000/mcL) in an otherwise healthy, term newborn
• Widespread petechiae, purpura, or cephalohematoma at birth
• Most devastating complication: Intracranial Hemorrhage (ICH), often occurs in utero or immediately postnatal
• Maternal platelet count is completely normal

Diagnosis

• Send maternal and paternal blood for HPA (Human Platelet Antigen) genotyping and maternal serum for anti-platelet antibodies
• Most common culprit antigen: HPA-1a (mother HPA-1a negative, baby HPA-1a positive)
• Cranial Ultrasound MUST be performed to rule out intracranial hemorrhage

Management

• Acute bleeding or high-risk (Plts < 30k): Transfuse matched HPA-antigen negative platelets (or maternal washed platelets)
• If unavailable, transfuse random donor platelets (may be destroyed, but provides some hemostasis) AND administer IVIG (1g/kg)
• Monitor serial platelet counts strictly (thrombocytopenia lasts 1-3 weeks depending on maternal antibody clearance)
• Corticosteroids are generally NOT recommended as first-line for the infant

Hematology & Transfusion Protocols

• PRBC Transfusion: 10-15 mL/kg administered slowly over 3-4 hours; monitor for volume overload and TACO.
• Platelet Transfusion: 10-15 mL/kg over 30-60 minutes.
• Phototherapy irradiance should check strictly >= 30 µW/cm²/nm at the infant's skin level.
• Monitor for rebound hyperbilirubinemia exactly 12 and 24 hours after discontinuing phototherapy lights.
• Shield eyes meticulously and document position check every hour while under phototherapy.

Standardized Discharge & Follow-Up Criteria

• Adequate weight gain explicitly > 15-30g/day over a continuous 3-5 day period.
• Maintenance of temperature in an open crib with standard clothing for 48 hours.
• Successful completion of the 90-120 minute Infant Car Seat Challenge.
• Caregiver successfully completed CPR training, rooming-in, and independent medication administration.
• Referrals placed for High-Risk Infant Follow-Up Clinic, Early Intervention (PT/OT), and appropriate sub-specialists.

Diagnostic & Management Algorithm

• NAIT Management Logic: [START] Petechiae + Plt < 50k in otherwise healthy term newborn -> [ACTION] Suspect NAIT -> [PHARMACOLOGY] IVIG 1g/kg / Transfuse HPA-1a/-5b negative matched platelets -> [EVALUATE] Head US for ICH

References

1. Bussel JB, Vanderhare R. Management of fetal and neonatal alloimmune thrombocytopenia. Transfus Apher Sci.
2. Curtis BR. Recent progress in understanding the pathogenesis of fetal and neonatal alloimmune thrombocytopenia. Br J Haematol.