Haploidentical parental hematopoietic stem cell transplantation in pediatric refractory Langerhans cell histiocytosis.

Children with MS-LCH that fail to respond to conventional chemotherapy have poor outcomes. HSCT represents a potential salvage approach. It has been applied in over 50 cases in recent years. HSCT can achieve greater disease control than chemotherapy, but it carries a high risk of transplant-related mortality; thus, the haploidentical parental HSCT is used infrequently in pediatric refractory LCH. We report the first successful haploidentical parental HSCT, with no T-cell depletion, in two girls, aged 26 months and five months, with refractory MS-LCH. The mothers were donors with 5/6 and 4/6 HLA matches, respectively. The conditioning regimen included busulfan + cyclophosphamide + etoposide + antithymocyte-globulin ± fludarabine; the GVHD prophylaxis was based on cyclosporine + methotrexate ± mycophenolate-mofetil ± zenapax. In both cases, the stem cells were sourced from peripheral blood and BM, which included CD34+ cells (13.17 × 10(6)/kg and 40.23 × 10(6)/kg, respectively). These patients survived and showed no signs of disease activity in 54- and 44-month post-HSCT follow-ups. Our results indicated that, for patients that fail chemotherapy delivered early in the disease, but do not show organ dysfunction progression, it may be possible to achieve successful haploidentical parental HSCT with a strong myeloablative regimen.