Thrombocytopenia and hemostatic disorders in chronic graft versus host disease.

Chronic graft versus host disease (cGVHD) is a major and frequent late complication in allogeneic stem cell transplantation recipients. Although thrombocytopenia in cGVHD patients is among the most consistent and strongest predictors of poor survival across many cGVHD studies, such correlation is still neither clearly explained nor well understood. Low platelet counts in the setting of cGVHD are associated with an increase in complications and treatment-related mortality, but usually not with higher relapse rate or engraftment failure rate. Bleeding might be occasionally increased along with, paradoxically, thrombosis. Hemostatic disorders in the context of cGVHD are significant complications with multifactorial etiology, including tissue injury with releasing microparticles, cytokine release, macrophage/monocyte clearance, CMV infection, production of transforming growth factor-beta, and low levels of thrombopoietin. Future clinical trials with agents that stimulate megakaryocytopoiesis or influence underlying impaired hemostasis mechanisms should investigate whether such interventions may improve outcomes in patients with cGVHD.