Neonatal isoimmune thrombocytopenia caused by type I CD36 deficiency having novel splicing isoforms of the CD36 gene.

Neonatal alloimmune thrombocytopenia (NAIT) occurs because of transplacentally acquired maternal platelet alloantibodies. Most of the alloantibodies are against human platelet antigens, but the alloantibody against CD36 is rare. A full-term female baby was delivered by a mother who experienced two spontaneous abortions. The baby had thrombocytopenia with cephalhematoma. The platelet count increased by immunoglobulin therapy (400 mg/kg) for 3 d. Platelet antibody was detected in the postpartum maternal serum. The specificity of the antibody directed against platelets was identified as anti-Nak(a) (CD36). Flow cytometric analysis showed no expression of CD36 in both platelets and monocytes from mother. Mutation analysis revealed two different splicing isoforms of maternal CD36 mRNA. One allele was exon 4 skipping, another was exon 9 skipping, both of which led to a frameshift and produced a truncated CD36 protein. These results indicate that NAIT is caused by maternal CD36 deficiency having CD36 splicing abnormalities.