hematology and oncology
Complications of Transfusion
Post transfusion purpura
Post-transfusion purpura is a very rare complication in which the platelet count falls rapidly 4 to 14 days after an RBC transfusion, causing moderate to severe Thrombocytopenia . Almost all patients are multiparous women who typically received RBC transfusion during a surgical procedure. The exact etiology is unclear. However, the most accepted hypothesis is that a patient who is negative for human platelet antigen 1a (HPA1a) develops alloantibodies due to exposure to HPA1a antigen from the fetus during pregnancy. Because stored RBCs contain platelet microparticles and because most (99%) donors are HPA1a positive, platelet microparticles from the donor blood may trigger an antibody response in previously sensitized patients (anamnestic response). Because these platelet microparticles attach to the recipient's platelets (and thus coat them with HPA1a antigen), the alloantibodies destroy the recipient's platelets, causing thrombocytopenia. The disorder resolves spontaneously as the antigen-coated platelets are destroyed. Patients develop purpura along with moderate to severe bleeding—usually from the surgical site. Platelet and red cell transfusions make the condition worse. The differential diagnosis usually includes Heparin-induced thrombocytopenia (HIT), although HIT is not associated with bleeding. Diagnosis is made by documenting HPA1a antibodies in the patient's plasma and absence of corresponding antigen on the patient's platelets. Treatment is high-dose IV immunoglobulins (1 to 2 g/kg as a single dose or divided into 2 doses) and avoidance of further transfusion of platelets or RBCs. Plasma exchange may be considered in severe cases and, for patients with severe bleeding, platelets donated by HPA1a-negative donors could be transfused if available. 