Post-transfusion purpura
When to suspect this adverse reaction?
This is a rare reaction wherein patients develop dramatic, sudden and self-limiting thrombocytopenia, typically 7 to 10 days after a blood transfusion.
Patients usually have a history of sensitisation by either pregnancy or transfusion.
Usual cause?
Alloimmunisation to platelet-specific antigens, most often Human Platelet Antigen 1a (HPA-1a).
While the immune specificity may be to a platelet-specific antigen, both autologous and allogeneic platelets are destroyed.
Investigation
Demonstrate antiplatelet antibody.
What to do?
Give intravenous immunoglobulin at 1 g/kg as a total dose and repeat as necessary.(1)
You have to make a request to the Blood Service or Jurisdictional Approver to access IVIg.
Antigen-negative platelets may be indicated if platelet transfusion is required but this is controversial.
Reference
- Jurisdictional Blood Committee for and on behalf of the Australian Health Ministers’ Conference. Criteria for the Clinical Use of Intravenous Immunoglobulin in Australia. Commonwealth of Australia, 2007.
