Abstract
We report a case of neonatal alloimmune thrombocytopenia (NAIT) associated with antibody directed against human platelet antigen (HPA) -5b. A female infant was transferred to our neonatal intensive care unit (NICU) on the first day of life because of smallness for date. The blood examination on admission showed thrombocytopenia without bleeding tendency. The screening for antibodies against HPA by a mixed passive hemagglutination (MPHA) procedure showed that the sera of her mother contained an antibody which reacted with the infant's and her father's platelets. Anti-HLA antibodies were not detected in either the serum of the infant or the mother, but a specific anti-HPA-5b was found in the mother's serum. Genotyping by polymerase chain reaction (PCR) -LuminexTM applied to HPA genes showed that the mother was the homozygote of HPA-5a and that the infant and father were the heterozygotes of HPA-5a and HPA-5b. The diagnosis of NAIT associated with the maternal anti-HPA-5b antibody was made. Thenumbers of platelets of the infant were above 15.0 × 104/μl without remarkable event at 15 days of age. Wediscuss the characteristics of this disease in the Japanese population and the antenatal and postnatal management.
