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A nationwide survey was conducted to clarify the clinical features and outcomes of Korean children with Langerhans cell histiocytosis (LCH). Korea Histiocytosis Working Party analyzed the data of 603 patients who were diagnosed with LCH between 1986 and 2010 from 28 institutions in Korea. Median age at diagnosis was 65 months (range, 0 to 276 mo). Bone was the most frequently affected organ (79.6%) followed by skin (19.2%). Initially, 419 patients (69.5%) had single-system involvement (SS), 85 (14.1%) with multisystem (MS) disease without risk organ involvement (MS-RO), and 99 (16.4%) multisystem disease with risk organ involvement (MS-RO). The 5-year overall survival (OS) rates in the SS, MS-RO, and MS-RO groups were 99.8%, 98.4%, and 77.0%, respectively (P

Background We evaluated the outcomes and prognostic factors, especially serum levels of alpha-fetoprotein (AFP) and their changes during the treatment of hepatoblastoma (HB). Procedure We retrospectively analyzed the medical records of 43 consecutive children with HB treated at a single institution between 1991 and 2010. Results Of 43 patients, 5 (12%) underwent primary tumor resection at diagnosis and 38 (88%) received preoperative chemotherapy. Of those 38 patients, 7 (16%) died of progressive disease during preoperative chemotherapy, and 31 (72%) underwent curative operations, including 5 who underwent liver transplantation, after a median 4 cycles of chemotherapy (range, 3–14 cycles). The 5-year overall survival and disease-free survival rates were 62.1 ± 8.3% and 65.6 ± 7.6%, respectively. AFP >263,000 ng/mL at diagnosis, a decline of

BACKGROUND Central nervous system (CNS) complications after allogeneic hematopoietic stem cell transplantation (HSCT) have not been well characterized in the pediatric population. METHODS We retrospectively analyzed data of 202 consecutive children who underwent allogeneic HSCT (60 from matched related donors, 9 from mismatched related donors, and 133 from unrelated donors) at Asan Medical Center between 1998 and 2009. RESULTS Twenty-seven children (13.5%) developed CNS complications within 6 months after HSCT. Calcineurin inhibitor (CNI)-associated neurotoxicity was the most common CNS complication (n=16), followed by CNS infection (n=2), cerebrovascular events (n=2), thrombotic microangiopathy-associated events (n=2), metabolic encephalopathy (n=2), irradiation/chemotherapy injury (n=1), and encephalopathy/myelopathy of unknown causes (n=2). Univariate analysis showed that a transplant from an alternative donor and the occurrence of acute graft-versus-host disease (GVHD) (>grade 2) were associated with a significantly increased risk of CNS complications. In the multivariate analysis, acute GVHD >grade 2 was identified as an independent risk factor for early CNS complications. The 5-year overall survival rate was significantly lower in patients with CNS complications (52.1% vs. 64.9%, P=0.014), whereas CNI-associated neurotoxicity did not affect the survival outcome. CONCLUSION CNS complications are frequent among children undergoing HSCT, contributing to early death after transplant. More attention should be paid to the development of CNS complications for recipients of alternative donor transplants and patients with severe acute GVHD who are at increased risk for CNS complications.

Familial hemophagocytic lymphohistiocytosis (familial HLH or FHL) is a potentially fatal autosomal recessive disorder. Our previous study demonstrated that UNC13D mutations (FHL3) account for ∼90 % of FHL in Korea with recurrent splicing mutation c.754-1G>C (IVS9-1G>C). Notably, half of the FHL3 patients had a monoallelic mutation of UNC13D. Deep intronic mutations in UNC13D were recently reported in patients of European descent. In this study, we performed targeted mutation analyses for deep intronic mutations and investigated on the founder effect in FHL3 in Korean patients. The study patients were 72 children with HLH including those with FHL3 previously reported to have a monoallelic UNC13D mutation. All patients were recruited from the Korean Registry of Hemophagocytic Lymphohistiocytosis. In addition to conventional sequencing of FHL2-4, targeted tests for c.118-308C>T and large intronic rearrangement mutations of UNC13D were performed. Haplotype analysis was performed for founder effects using polymorphic markers in the FHL3 locus. FHL mutations were detected in 20 patients (28 %). Seventeen patients had UNC13D mutations (FHL3, 85 %) and three had PRF1 mutations (FHL2, 15 %). UNC13D:c.118-308C>T was detected in ten patients, accounting for 38 % of all mutant alleles of UNC13D, followed by c.754-1G>C (26 %). Haplotype analyses revealed significantly shared haplotypes in both c.118-308C>T and c.754-1G>C, indicating the presence of founder effects. The deep intronic mutation UNC13D:c.118-308C>T accounts for the majority of previously missing mutations and is the most frequent mutation in FHL3 in Korea. Founder effects of two recurrent intronic mutations of UNC13D explain the unusual predominance of FHL3 in Korea.

The role of allogeneic hematopoietic stem cell transplantation (HSCT), including transplantation from an alternative donor (AD), has not been clearly defined for children with high-risk or advanced acute myeloid leukemia (AML). We retrospectively reviewed outcomes in 29 children (median age at HSCT, 6.7 y; range, 1.0-16.2 y) with high-risk or advanced AML who underwent allogeneic HSCT at the Asan Medical Center between 1998 and 2008. Donors included a matched sibling donor (MSD) for 7 patients (24%), an unrelated volunteer for 21 patients (72%), and a haploidentical mother for 1 patient (3%). The 3-year estimates of overall survival and event-free survival (EFS) were 77% [95% confidence interval (CI), 65%-99%] and 70% (95% CI, 57%-93%), respectively, whereas the cumulative incidences of relapse and transplant-related mortality were 33% (95% CI, 5%-58%) and 7% (95% CI, 0%-44%), respectively. The 3-year EFS rates did not differ between MSD and AD HSCT. Univariate analysis showed that age ≥ 10 years at diagnosis was the only factor associated with poorer EFS. Development of acute graft-versus-host disease predicted a significantly lower incidence of relapse. These findings may provide further evidence that allogeneic HSCT is a curative therapy for children with high-risk or advanced AML, and suggest the efficacy of AD transplantation.

Background The impact of HLA matching on outcomes of unrelated donor (URD) hematopoietic stem cell transplantation (HSCT) varies in different racial or ethnic groups. Since little is known about the impact of such matching on URD HSCT in Korean children, we analyzed this issue. Methods We analyzed the outcomes of 142 patients who underwent URD HSCT at 4 Korean medical centers. All patient donor pairs were fully typed for HLA-A, -B, -C, and -DR alleles. Results At a median follow-up of 22 months, 3-year survival rates for patients with 8, 7, and ≤6 matched alleles were 88.4%, 70.7%, and 53.6%, respectively. A single mismatch (Mm) at HLA-B or -C was associated with lower survival compared with that associated with 8 matched alleles. No significant differences were observed between single-allele and single-antigen Mms with respect to survival rate or acute graft-versus-host disease (aGVHD) incidence rates. HLA disparity had a greater impact on the survival of patients with high-risk malignancy than of those with low-risk malignancy. Among pairs with a single Mm, only locus A showed a significant association and higher risk of grade III-IV aGVHD compared to those in patients with 8 matched alleles. Conclusion Disparity in HLA class I, regardless of antigen or allele Mm, adversely affected both survival and grade III-IV aGVHD development. An increased number of HLA Mms was associated with a higher risk of post-transplantation complications. Further investigations using larger cohorts are required to confirm the effects of HLA mismatching on URD HSCT patient outcomes.

Iron overload is a significant clinical problem in patients with severe aplastic anemia or other transfusion-dependent bone marrow failure diseases. Iron chelation therapy is more readily available owing to the recent introduction of oral iron chelators. We describe 2 cases of children with severe aplastic anemia and related transfusional iron overload who received iron chelation therapy with oral deferasirox. Our patients experienced restoration of trilineage hematopoiesis after the administration of deferasirox along with the reduction in ferritin levels, and subsequently became transfusion-free. Our report raises the possibility of potential benefit on hematopoiesis from iron chelation therapy and warrants furthermore investigations.

Background Immune reconstitution (IR) after hematopoietic stem cell transplantation (HSCT) reduces transplantation-related complications such as infection and improves HSCT outcomes. Methods We retrospectively analyzed IR of lymphocyte subpopulations in 38 pediatric patients for hematologic malignant diseases after allogeneic HSCT from April 2006 to July 2008. T-cell-, B-cell-, and natural killer (NK) cell-associated antigens were assayed in peripheral blood by flow cytometry analysis of 5 lymphocyte subsets, CD3+, CD3+/CD4+, CD4+/CD8+, CD16+/CD56+, and CD19+, before and 3 and 12 months after transplantation. Results Reconstitutions of CD16+/CD56+ and CD3+/CD8+ lymphocytes were achieved rapidly, whereas that of CD3+/CD19+ lymphocytes occurred later. Age was not related to reconstitution of any lymphocyte subset. Total body irradiation (TBI) and anti-thymocyte globulin (ATG) administration were related to delayed reconstitution of total lymphocytes and CD3+ lymphocytes, respectively. Reconstitutions of CD3+/CD4+ lymphocytes and CD3+/CD8+ lymphocytes were significantly delayed in patients who received umbilical cord blood stem cells. In patients with chronic graft-versus-host disease (cGVHD), recovery of the total lymphocyte count and CD19+ lymphocytes at 3 months post-transplant were significantly delayed. However, acute GVHD (aGVHD) and cytomegalovirus (CMV) reactivation did not influence the IR of any lymphocyte subset. Further, delayed reconstitution of lymphocyte subsets did not correspond to inferior survival outcomes in this study. Conclusion We observed that some lymphocyte reconstitutions after HSCT were influenced by the stem cell source and preparative regimens. However, delayed CD19+ lymphocyte reconstitution may be associated with cGVHD.

Abstract 4730 Background: Familial hemophagocytic lymphohistiocytosis (FHL) is a potentially fatal disease with an autosomal recessive inheritance. Mutations in the UNF13D gene (FHL3) are the major genetic background of Korean patients with FHL (∼90). In particular, a single splicing mutation, IVS9-1G>C, is recurrent and accounts for the majority of mutant alleles (>50%), suggesting a founder effect. In this regard, the authors investigated the signature of founder effect in Korean patients with FHL3. Methods: The study patients were 17 pediatric patients with FHL3 recruited from the Korean Registry of HLH between January 2007 and June 2010. Nine patients had 1 (n=8) or 2 (n=1) mutant alleles of IVS9-1G>C. Haplotypes of the genomic region of UNC13D were reconstructed using the genotype information of short tandem repeat (STR) and single nucleotide polymorphism (SNP) markers in a set of 192 control chromosomes of Korean descent. The haplotypes of the 17 patients were assigned and analyzed with respect to the mutation status. Results: Fifteen haplotypes (Ht1-Ht15) were reconstructed based on the genotype data from 5 common SNPs of UNC13D (rs7210574, rs2290770, rs7223416, rs3744007, and rs3744010) in the control group. Haplotype analyses in the control group demonstrated that Ht3 was remarkably more prevalent in the patient group than in the control group (55.0% vs. 31.3%), and all 9 patients with IVS9-1G>C had Ht3. In addition, all patients with IVS9-1G>C except one had the 258 allele of a polymorphic STR marker near UNC13D (DS19S1839). Conclusions: The results suggested a founder effect in the recurring mutation IVS9-1G>C of UNC13D in Korean patients. This observation may explain the unusually high proportion of FHL3 in Korea. Disclosures: No relevant conflicts of interest to declare.

Abstract 4807 Background: Hematopoietic microenvironment consists of endosteal and vascular microenvironment. Osteopontin and osteonectic are released by osteoblast which is one of the factors regulating endosteal microenvironment. CXCL12 and CXCR4 are included in the factors regulating vascular microenvironment. Markers indicating the degree of differentiation of hematopoietic stem cells (HSC) include CD133, CD34 and CD117. This study is to evaluate the expression pattern of markers of hematopoietic microenvironment and HSC in childhood acute lymphoblastic leukemia (ALL) at diagnosis and the changes of them after chemotherapy. Methods: Between January, 2007 and December, 2009, 32 patients were diagnosed as ALL at Asan Medical Center. Bone marrow (BM) biopsies were obtained at diagnosis, after induction, consolidation, interim maintenance and delayed intensification. There were 22 male and 10 female patients with a mean age of 7.33 years. The diagnoses were a common cell ALL in 29. By immunohistochemistry, we analyzed the expressions of CD133, CD34, CD117, osteopontin, osteonectin, CXCL12, and CXCR4 in these BM biopsy specimens. Results: CD133+ cells decreased at diagnosis, and recovered after consolidation. The CD34+ cells decreased after induction, and then gradually increased again. CD117+ cells were fewer at diagnosis, but increased after chemotherapy. The expression of osteopontin was depressed at diagnosis, and gradually recovered. The expression of osteonectin was also suppressed at diagnosis and recovered after delayed intensification. CXCL12 was suppressed at diagnosis, recovered after consolidation and decreased after delayed intensification. CXCR4 was also suppressed at diagnosis, but increased after therapy. Conclusions: This study is the first report on the changes of hematopoietic microenvironment and HSC of childhood ALL at diagnosis and after chemotherapy, evaluated by immunohistochemistry. CD133+ cells, CD34+ cells and CD117+ cells increased in the reconstructive phase. CD34 can be a marker reflecting the BM recovery. Proliferation of osteoblasts and stromal cells were active after interim maintenance. The reconstruction of HSC and BM matrix increased after consolidation. The recovery of BM microenvironment was established after consolidation and interim maintenance chemotherapy. These findings may serve as basic data for future studies dealing with the hematopoietic microenvironment and HSC of childhood ALL. Disclosures: No relevant conflicts of interest to declare.