Bone Marrow Necrosis and Elevated Plasma Levels of Fas Ligand in a Patient with Aggressive Natural Killer Cell Leukemia

Fas is type I membrane protein, expressed on various tissue including hematopoietic cell. Its ligand (FasL), a member of the tumor necrosis factor (TNF) family, which includes two forms of a membrane-bound form and a soluble one, induces apoptosis of Fas-bearing cells through cytotoxic activity. FasL is undetectable in the serum of healthy person, whereas it is high in that from patients with T-large granular lymphocytic leukemia and natural killer (NK) cell lymphoma. We experienced a case of aggressive NK cell leukemia presenting severe bone marrow necrosis (BMN) after administrating granulocyte colony stimulating factor (G-CSF). In concern with a relation to cytokine, his serum FasL was examined and found to be extremely elevated. Administration of G-CSF under a large quantity of soluble FasL might play an important role in the pathogenesis of BMN through apoptosis of hematopoietic cells in the bone marrow.