Pembrolizumab-induced Pure Red Cell Aplasia Successfully Treated with Intravenous Immunoglobulin.

We herein report a 64-year-old man who was treated with pembrolizumab for relapsed Hodgkin lymphoma. After the third administration of pembrolizumab, he showed acute anemia with a positive direct anti-globulin test. Because of the markedly erythroid hypoplasia, he was diagnosed with pure red cell aplasia (PRCA) caused by pembrolizumab. He was initially treated with prednisolone, but the reticulocytes decreased after tapering prednisolone. He then received high-dose intravenous immunoglobulin (IVIG) with prednisolone, and PRCA was successfully treated. Although the pathogenesis of PRCA caused by immune checkpoint inhibitors (CPIs) remains unclear, IVIG treatment may be effective for some steroid-refractory CPI-induced PRCA cases.