Neonatal alloimmune thrombocytopenic purpura: key points.
| Incidence: 1 per 3000 in a retrospective study; 1 per 2200 births in one prospective study. |
| Maternal antibodies produced against paternal antigens on fetal platelets. |
| Similar to erythroblastosis fetalis except that 50% of cases may occur during first pregnancy. |
| Most frequently implicated antigens are HPA-1a and HPA-5b (United States/Europe). |
| Sensitized mothers should expect increasing titers with each subsequent pregnancy when fetal platelets express the paternal antigen, lengthening the duration of neonatal thrombocytopenia. |
| Sisters of sensitized mothers are at risk due to the HLA-associated rate of alloantibody production: |
| In the case of responsiveness to HPA-1a, there is a high-risk association with HLA DRB3*0101 or DQB1*02. |
| In the case of responsiveness to HPA-6b, there is an increased association with HLA DRB1*1501, DQA1*0102 or DQB1*0602. |
| Incidence: 1 per 3000 in a retrospective study; 1 per 2200 births in one prospective study. |
| Maternal antibodies produced against paternal antigens on fetal platelets. |
| Similar to erythroblastosis fetalis except that 50% of cases may occur during first pregnancy. |
| Most frequently implicated antigens are HPA-1a and HPA-5b (United States/Europe). |
| Sensitized mothers should expect increasing titers with each subsequent pregnancy when fetal platelets express the paternal antigen, lengthening the duration of neonatal thrombocytopenia. |
| Sisters of sensitized mothers are at risk due to the HLA-associated rate of alloantibody production: |
| In the case of responsiveness to HPA-1a, there is a high-risk association with HLA DRB3*0101 or DQB1*02. |
| In the case of responsiveness to HPA-6b, there is an increased association with HLA DRB1*1501, DQA1*0102 or DQB1*0602. |