Pregnancy-associated autoimmune neonatal thrombocytopenia: role of maternal HLA genotype

In a prospective study between 1993 and 1998, data was collected from 46 pr egnant women and subsequently from their babies. 75 pregnant women with act ive autoimmune thrombocytopenic purpura (AITP) or a history of,AITP (groupA ) and 21 pregnant women with isolated thrombocytopenia and identification o f specific platelet autoantibodies detected by monoclonal antibody-specific immobilization of platelet antigens (MAIPA) assay (group B) were evaluated for platelet-associated immunoglobulin-G (PAIgG). MAIPA assay and HLA geno type. Neonatal platelet counts were performed at least three times in the f irst week;. 11 neonates were thrombocytopenic (23.9%). No severe haemorrhag e occurred. There were no significant differences regarding the values of P AIgG or positive MAIPA tests between mothers of thrombocytopenic or healthy newborns. A significant difference, however, regarding the HLA DRB3* allel e was found, with a high incidence in the subgroup of mothers of healthy ne wborns (P = 0.005). A similar trend was found among mothers with anti-GPIIb IIIa antibodies (P = 0.06). In contrast, HLA DRB5* allele appeared to be pr esent especially in mothers of thrombocytopenic newborns (not significant). Our data suggest that mothers with AITP who have the HLA DRB3* genotype ar e unlikely to give birth to a thrombocytopenic baby This study provides a p reliminary report on a noninvasive test to identify infants who are likely to be affected.