Multiple extramedullary relapses without bone marrow involvement after second allogeneic hematopoietic stem cell transplantation for acute myeloid leukemia

EMR without BM involvement after allogeneic HSCT is extremely rare, especially in children; only a few cases have been reported. A two-yr-old boy was diagnosed with AML (M4) and underwent allogeneic HSCT in first complete remission with BM from HLA-matched unrelated donor without GVHD. Four yr later, he had a BM relapse and after induction and consolidation chemotherapy, he received a second HSCT from an unrelated donor using peripheral blood stem cells. His second post-transplant course was complicated by extensive chronic GVHD involving the skin, oral cavity, and lungs, which was treated with tacrolimus and corticosteroid. Two yr later, he noticed a mild swelling in the right cheek area. The BM showed a complete remission marrow and a soft tissue biopsy was compatible with granulocytic sarcoma. PET-CT showed multifocal bone involvements. He received chemotherapy, and the chloromas decreased in size. We report a case of diffuse EMR of AML without BM involvement after a second allogeneic HSCT.