Stable hematopoietic cell engraftment after low-intensity nonmyeloablative conditioning in patients with immune dysregulation, polyendocrinopathy, enteropathy, X-linked syndrome

BackgroundImmune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome is characterized by severe systemic autoimmunity caused by mutations in the forkhead box protein 3 (FOXP3) gene. Hematopoietic cell transplantation is currently the only viable option for long-term survival, but patients are frequently very ill and may not tolerate traditional myeloablative conditioning regimens.ObjectiveHere we present the outcome of hematopoietic cell transplantation using a low-intensity, nonmyeloablative conditioning regimen in 2 patients with IPEX syndrome and significant pretransplant risk factors.MethodsTwo high-risk patients with IPEX syndrome received HLA-matched related bone marrow or unrelated peripheral blood stem cell grafts following conditioning with 90 mg/m2 fludarabine and 4 Gy total body irradiation. Postgrafting immunosuppression consisted of mycophenolate mofetil and cyclosporine. Immune reconstitution and immune function was evaluated by measurement of donor chimerism, regulatory T-cell numbers, absolute lymphocyte subsets, and T-cell proliferation assays.ResultsBoth patients experienced minimal conditioning toxicity and successfully engrafted after hematopoietic cell transplantation. With a follow-up of 4 and 1 years, respectively, patients 1 and 2 have full immune function and normal FOXP3 protein expression.ConclusionA low-intensity, nonmyeloablative conditioning regimen can establish stable engraftment and correct the life-threatening immune deficiency and enteropathy of IPEX syndrome despite the presence of comorbidities that preclude conventional hematopoietic cell transplantation.