Atraumatic Splenic Rupture Due to Ectopic Extramedullary Hematopoiesis after Autologous Stem Cell Transplantation in a Patient with AL Amyloidosis

A 50-year-old man was diagnosed with multiple myeloma complicating AL amyloidosis. Splenic rupture was complicated during autologous stem cell transplantation (auto-SCT). Granulocyte colony-stimulating factor (G-CSF) was not administered. A pathological examination of the spleen revealed that CD34-positive cells were concentrated in the ruptured part of the splenic capsule. Hematopoietic cells were engrafted in the small gap between the capsule and amyloid protein deposition area of the spleen, which might have caused the splenic rupture in the absence of G-CSF administration. Special attention is thus required for amyloidosis patients undergoing auto-SCT, even when G-CSF is not administered.