Splenectomy for Severe Autoimmune Cytopenias after Allogeneic Stem Cell Transplantation: Case Report

Autoimmune hematological diseases after allogeneic hematopoietic stem cell transplantation in children: an Italian multicenter experience

Autoimmune hematological diseases (AHDs) may occur after allogeneic hematopoietic stem cell transplantation (HSCT), but reports on these complications in large cohorts of pediatric patients are lacking. Between 1998 and 2011, 1574 consecutive children underwent allogeneic HSCT in 9 Italian centers. Thirty-three children (2.1%) developed AHDs: 15 autoimmune hemolytic anemia (45%), 10 immune thrombocytopenia (30%), 5 Evans' syndrome (15%), 2 pure red cell aplasia (6%), and 1 immune neutropenia (3%). The 10-year cumulative incidence of AHDs was 2.5% (95% confidence interval, 1.7 to 3.6). In a multivariate analysis, the use of alternative donor and nonmalignant disease was statistically associated with AHDs. Most patients with AHDs (64%) did not respond to steroids. Sustained complete remission was achieved in 87% of cases with the anti-CD20 monoclonal antibody (rituximab). Four patients (9%) (1 autoimmune hemolytic anemia, 1 Evans' syndrome, 2 immune thrombocytopenia) died at a median of 87 days after AHD diagnosis as a direct or indirect consequence of their disorder. Our data suggest that AHDs are a relatively rare complication occurring after HSCT that usually respond to treatment with rituximab.

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.

Sites and kinetics of donor thrombopoiesis following transplantation of whole bone marrow and progenitor subsets

INTRODUCTION

Little is known about the sites and kinetics of thrombopoiesis following bone marrow transplant. The spleen is a site of hematopoiesis in a healthy mouse, and hematopoietic activity increases in response to stress. We hypothesized that the spleen is a major site of early post-transplant thrombopoiesis.

METHODS

We transplanted whole bone marrow (WBM) or lineage depleted progenitor subsets fractionated based on expression of c-kit and Sca-1 from transgenic mice expressing green fluorescent protein into lethally irradiated C57BL/6 recipients. We also transplanted whole bone marrow cells into healthy and splenectomized mice. Post-transplant megakaryopoiesis was assessed by measuring circulating platelet number, percent donor-derived platelets, bone marrow cellularity, splenic weight, megakaryocyte size, and megakaryocyte concentration from hour 3 to day 28 post transplant.

RESULTS

Following transplant, circulating donor-derived platelets were derived only from c-kit expressing subsets. Donor-derived platelets first appeared on post-transplant day five. Splenectomy reduced the number of these earliest circulating platelets. Splenic megakaryopoiesis increased dramatically from day 7-14 post-transplant. However, splenectomy accelerated platelet engraftment during this time frame.

CONCLUSION

Overall, these results demonstrate that the first platelets are produced by c-kit expressing megakaryocyte progenitors in the bone marrow and spleen. After post-transplant day 5, the net effect of the spleen on thrombopoiesis is to slow engraftment due to immune effects or hypersplenism.