OR34 Platelet refractoriness in a patient with 0% PRA due to a rare anti-CD36(NAKa) antibody

Platelet transfusion refractoriness in patients with hematological malignancies ranges from 7% to 34%. The etiology of platelet refractoriness in this patient population is typically attributable to due to formation of HLA antibodies (Abs) from pregnancy or previous transfusion. We report platelet refractoriness in the setting of induction chemotherapy for AML from allo-Abs to NAK a antigen/CD36/glycoprotein (GP) IV. A 66yo AAF presented with transfusion dependent AML with 70% circulating peripheral blasts and started on 7 + 3 regimen. She developed profound thrombocytopenia and her platelet count was 0 by day 13. As part of her evaluation for refractoriness, HLA antibody screening was done, but was negative. An Immucor ELISA assay was then performed and revealed positive Abs to GPIV (NAK a antigen/CD36). Abs against GPIIb/IIIa, GPIa/IIa, GPIb/IX, and HLA Class I were all negative. GPIV Abs were confirmed by Blood Center of Wisconsin using monoclonal Ab MBC 131.7 against CD36. Cross-matching was performed at our institution with multiple single donor apheresis platelets, all showing strong positive reactivity. Because CD36 in these units may be soluble, an incompatible leukoreduced, irradiated and washed single donor platelet unit was given which was tolerated well with a resultant increase to 14,000/ μ L. Despite strong reactivity of this unit in the crossmatch, the patient’s platelet count increased and 1 week later was 16,000/μL despite no transfusion support. Platelet refractoriness in the setting of hematological malignancy is well documented. Abs develop from prior pregnancy and transfusion in the setting of prolonged pancytopenia in hematological malignancies. Typically, allo-Abs develop against platelet membrane structures including human platelet antigens, HLA antigens, and rarely NAK a antigen on the CD36 glycoprotein molecule. CD36 is expressed in almost 100% of white Europeans and is not detectably expressed by 2% of sub-Saharan Africans and 10% of Asians. CD36 is a soluble antigen and is expressed on various cells such as erythroblasts and monocytes. We propose that washing platelets may be a useful strategy in treating platelet refractoriness in patients with abs to NAK a antigen as finding CD36 negative donors is extremely difficult and few blood banks in North America test donors for this antigen.