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Background Fanconi anemia (FA) is a condition characterized by congenital malformations, low height, and progressive bone marrow failure during childhood, genomic instability and hypersensitivity to DNA cross-linking agents. Bone marrow transplantation (BMT), is currently the only treatment capable to restore normal hematopoiesis and improve survival of these patients. To achieve a successful allogeneic BMT, a normal T-cell immunity reconstitution is required.1,2 Objective To describe the kinetics of immune reconstitution in six patients with FA after BMT, having used a reduce intensity conditioning regimen, well as associated infections during the post-transplant process. Methods We describe the distribution in peripheral blood of CD3+ T lymphocytes, CD16 +/CD56+ NK cells, CD4+ helper T lymphocytes, CD8+ cytotoxic T lymphocytes and CD19+/CD20+ B cells, in six patients with FA, after BMT from an HLA-matching sibling and complete chimerism, on days +90, +120, +150, +180, +210 and +360. The conditioning regimen employed consisted of fludarabine (Flu) 150 mg/m2, cyclophosphamide 20 mg/kg and rabbit anti-thymocyte globulin (r-ATG) 20 mg/kg. Infection was determined by a positive reaction of the DNA polymerase chain to Cytomegalovirus (CMV), Epstein-Barr virus, Adenovirus and BK virus (BKV), as well as galactomannan antigen and antibodies against Candida sp, or positive bacterial cultures. Results We observed different kinetics regarding the recovery of different lymphocyte subpopulations, starting from day +90. CD16+/CD56+ NK cells recovered first, between days 90 and 120, followed by CD8+ T lymphocytes between day +120 and +150, CD19+/CD20+ B cells between day +180 and +210, and finally, CD4+ T lymphocytes starting from day 210. Five patients presented infection in the post-BMT stage. Four patients before +90, developed CMV infection, based on positive reaction of the CMV polymerase chain. All patient responses to ganciclovir therapy and no CMV disease were documented. The fifth patient presented with meningitis due to Lysteria monocitogenes and BKV hemorrhagic cystitis at day +153; this patient had the diagnosis of chronic-graft versus host disase, and was treated with ampicillin, rifampicin and intravenous immunoglobulin, evolving satisfactorily. All patients remain alive and well. Discussion Most patients in our report developed CMV infection, as being reported with FLU and anti-thymocyte globulin combination. We observed a later reconstitution in comparison with patients in whom lower doses of r-ATG ( Conclusion Immunological reconstitution after a BMT in FA patients is determinant for morbidity and mortality, mainly due to opportunistic infections and GVHD. We observed that recovery kinetics of different lymphocyte populations is different in cases in which higher doses of r-GAT are used, also an early detection and prompt treatment of opportunistic infections may be determinant for patient's survival. Conflict-of-interest disclosure: The authors declare they have nothing to disclose. Correspondence: Gerardo López-Hernández. loherge@gmail.com BibliographyOgonek J, Kralj Juric M, Ghimire S, Varanasi PR, Holler E, Greinix H, et al. Immune reconstitution after allogenic hematopoietic stem cell transplantation. Front immunol. 2016; 7 (507):1-15.Smith AR, Wagner JE. Current clinical management of Fanconi anemia. Expert Rev Hematol. 2012; 5 (5): 513-522.Perlingeiro-Beltrame M, Malvezzi M, Bonfim C, Tadeu Covas D, Pasquini R. Immune reconstitution in patients with Fanconi anemia after allogeneic bone marrow transplantation. Cytotherapy. 2014; 0: 1e14. Disclosures No relevant conflicts of interest to declare.

Background Hematopoietic stem cell transplantation (HSCT) is used in pediatric patients with acute leukemia, after a relapse to bone marrow, or in first remission in case of high risk disease. If necessary, 75% of the cases do not have a compatible related donor and it is not always possible to have a compatible unrelated donor or an umbilical cord blood unit. Therefore, using haploidentical alternative donors of hematopoietic stem cells (HSC) is becoming more frequent. Objective The purpose of this is to report the results of haploidentical hematopoietic stem cell transplantation with post-transplant cyclophosphamide (PTCy) in a group of pediatric patients, which lacks a related HLA compatible donor, at the National Pediatrics Institute in México City, México, in the period between January 2012 thru December 2016. Methods We retrospectively reviewed 27 patients´ files Results Fourteen patients (51.6%) presented complete and sustained chimerism. Overall survival is presented in Figure 1. Graft failure occurred (48.1%) more frequently in the group of patients in whom bone marrow was used as a source of HSC (p=0.26). Nine patients with complete chimera, whose HSC source turned out to be PB, presented acute-GVHD III-IV (p = 0.06). Four of the patients whom presented full engraftment died, three of them due to infectious processes (cytomegalovirus pneumonia, AH1N1 pneumonia, abdominal sepsis secondary to intestinal perforation and E. coli sepsis), before +100-day post-transplantation. All these patients presented acute-GVHD III-IV. The fourth patient who died, also the cause was infectious (pulmonary sepsis secondary to Morganella morganii), thirteen months after the transplant and without history of GVHD. Of the thirteen patients who presented primary graft failure, seven of them are alive and without evidence of tumoral activity Discussion Haploidentical transplantation with PTCy is a feasible therapeutic option in pediatric patients with malignant hematological diseases who require a HSCT and do not have a matched sibling or unrelated donor available. Conflict-of-interest disclosure: The authors declare they have nothing to disclose. Correspondence: Gerardo López-Hernández. loherge@gmail.com BibliographyKlein OR, Buddenbaum J, Tucker N, et al. Nonmyeloablative Haploidentical Bone Marrow Transplantation with Post-Transplant Cyclophosphamide for Pediatric and Young Adult Patients with High-Risk Hematologic Malignancies. Biol Blood Marrow Transplant. 2017; 23(2): 325-332.González-Llano O, González-López EE, Ramírez-Cázares AC, et al. Haploidentical peripheral blood stem cell transplantation with posttransplant cyclophosphamide in children and adolescents with hematological malignancies. Pediatr Blood Cancer. 2016; 63: 2033-2037.Robinson TM, O'Donnell PV, Fuchs EJ, Luznik L. Haploidentical bone marrow and stem cell transplantation: experience with post-transplantation cyclophosphamide. Semin Hematol. 2016; 53(2): 90-97.Fuchs EJ, Huang XJ, Miller JS. HLA-haploidentical stem cell transplantation for hematologic malignancies. Biol Blood Marrow Transplant. Biol Blood Marrow Transplant. 2010; 16 (1 Suppl): S57-S63. Disclosures No relevant conflicts of interest to declare.

Background: Philadelphia-like (Ph-like) subtype occurs in 15-20% of children patients diagnosed with precursor B cell (PCB) acute lymphoblastic leukemia (ALL). It is characterized by alterations in kinases and their receptors, affecting signaling pathways such as Jak2-Stat5, class Abl and Ras. It is particularly frequent (35%) in Hispano-Latino high risk PCB-ALL patients, residing in the USA. In Mexico, based on our ethnicity and the poor response to treatment of PCB-ALL pediatric patients, the Ph-like subtype could be frequent. However, this entity is widely variable and the diagnosis is based on genomic methods. In our country the incidence of leukemia is high, 78.1/1,000,000, and 83% of these cases are ALL. Therefore, it is important to detect Ph-like patients using diagnostic methods accessible to Institutions that treat patients with leukemia in our country. Aims: To develop an algorithm adapted to our local capacity for the diagnosis of Ph-like ALL children in Mexico. To determine the frequency of Ph-like patients in two Pediatric Institutions in our country Hypothesis: Ph-like ALL frequency in Mexican children will be higher than that reported in Hispano-Latino PCB-ALL patients. Methods, study design and laboratory studies: Bone marrow samples from 119 PCB-ALL patients (18≤ years old) at diagnosis were studied. Samples were collected at the Instituto Nacional de Pediatría and the Hospital Infantil de México Federico Gómez in Mexico City. Patients with recurrent gene fusions, ETV6-RUNX1, TCF3-PBX1,KMT2A-var and BCR-ABL1, were excluded. The Ph-like status of each patient was determined using molecular and biochemical methods. We analyzed a gene expression signature conformed by the genes: CRLF2, TSPN7, IGJ, PON2, SEMA6A and BMPR1B (q-RT-PCR), and detected the P2RY8-CRLF2 deletion (RT-PCR) in all patients. In those patients with overexpression of CRLF2, but negative to P2RY8-CRLF2, the IGH-CRLF2 rearrangement (FISH) was examined. The positive cases to P2RY8-CRLF2, without overexpression of CRLF2, were analyzed looking for minor subclones (FISH) with the deletion. IKZF1 deletions (nested RT-PCR) were analyzed in all patients. The biochemical studies included CRLF2 protein expression, phosphoflow analysis of Jak2-Stat5, class Abl and Ras targets (flow cytometry). All these assays were performed whenever the cell sample allowed it. Patients with two or more of the following characteristics were considered as Ph-like cases: with overexpression of 50% or more of the expression signature, positive to P2RY8-CRLF2 or IGH-CRLF2, alteration of one or more signaling pathways, with IKZF1 deletions. Results: In 50% (n=74) of patients CRLF2 overexpression was detected, within them 15% were positive to P2RY8-CRLF2 deletion, 17% to IGH-CRLF2 rearrangement, and 18% had an unidentified CRLF2 alteration that cause the overexpression. Within the 50% of cases without CRLF2 overexpression, 18% were positive to the P2RY8-CRLF2 rearrangement. IKZF1 deletion was evaluated in 55 patients and 72% were positive. Results obtained revealed a high frequency of CRLF2 and IKZF1. In 68 patients the gene expression profile was evaluated, 60% presented overexpression of 50% or more genes. The biochemical analysis revealed that 67% (n=42) of patients were positive to CRLF2 protein, 29% (n=21) had abnormal Jak2/Stat5 activation, 34% (n=32) presented abnormal Abl activation, and in 43% (n=7) abnormal Ras activation was detected. Not all the CRLF2 protein positive patients presented Jak2-Stat5 pathway activation (2%). Patients with more than one abnormal pathway were detected (18% with Jak2-Stat5/Abl or Abl/Ras, n=21). Based on our algorithm of analysis, 53% of the analyzed patients present genetic and biochemical characteristics of the Ph-like subtype. Conclusions: The combined methods contributed to identify Ph-like patients, the results demonstrate that the frequency of PCB-ALL children with Ph-like characteristics in Mexican patients is higher compared to other populations. This study demonstrates high frequency of CRLF2 alterations and IKZF1 deletions in PCB-ALL in Mexican population. In our experience, analysis of the pathway activation assays and the identification of CRLF2 and IKZF1 alterations are required to detect Ph-like patients. These results could be useful to stratify the childhood PCB-ALL patients in our country. Acknowledgments: CONACYT: PDCPN-2004/248591; Cátedra 2038. Disclosures No relevant conflicts of interest to declare.