171-P

Abstract

Aim Immune thrombocytopenia (ITP) is defined by persistent low platelet count less than 105/mm3 in the absence of other causes. The pathogeny includes anti-platelet antibodies. Platelet transfusion is rare in ITP, however may be helpful to treat life-threatening hemorrhages. Methods Platelet and HLA-specific antibodies were detected by ELISA. Anti- HLA class I antibodies were identified by Luminex single antigen beads. HLA typing for patient and spouse were done by rSSO. Results 72 year old female was admitted in the emergency room with confusion, extensive petechiae, purpura, echymosses, intracranial and pulmonary hemorrhages and severe thrombocytopenia (2000/mm3). Eight units of platelets were transfused, however the platelet count remained the same. Refractoriness to transfusion was assessed. Patient exhibited both platelet-specific (1a, 1b, 3a, 3b, 4a, 5a, 5b) and anti-HLA antibodies (PRA 80%), explained by only 2 specificities – HLA -A3 and w4 epitope (Fig. 1a). The HLA typing revealed HLA-A3 and B57(w4) as mismatched antigens in husband (patient had 3 pregnancies), while patient HLA was w6. The IgG subtype analysis demonstrated IgG1, which is a strong complement binder and it explained the massive and rapid platelets destruction after receiving the transfusion (Fig. 1b). Download : Download full-size image Conclusions The lack of post-transfusion platelet increment was caused by anti-HLA and platelet specific antibodies, as a result of pregnancy sensitization. In this dramatic case, diagnosis through alloantibody identification and HLA typing supported adequate therapy, with Rituximab and splenectomy, and patient survived a life threatening condition.