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BackgroundT-cell depleted (TCD) haploidentical transplantation using CD3+/CD19+ and TCRαβ+/CD19+ depletion techniques has been increasingly used in children with hematological malignancies. We present a retrospective study aimed to compare transplant outcomes in children with leukemia receiving a TCD haploidentical transplant using either CD3+/CD19+ or TCRαβ+/CD19+ platforms.MethodsA total of 159 children with leukemia (ALL=80) (AML=79) that received a TCD haploidentical transplantation using either CD3+/CD19+ (n=79) or TCRαβ+/CD19+ (n=80) platforms between 2005 and 2020 were included. Median age was 9 years in both groups. There were no differences in patient, donor, and transplant characteristics between groups except for donor KIR B genotype more frequent in the TCRαβ+/CD19+ group (91%) than in the CD3+/CD19+ group (76%) (p=0.009) and a high number of NK+ cells and lower CD19+ cells infused in the TCRαβ+/CD19+ group (35.32x106/kg and 0.06 x106/Kg) than in the CD3+/CD19 group (24.6x106/Kg and 0.25 x106/Kg) (p=0.04 and p=0.0001), respectively. Conditioning was based on TBF. Median follow-up for survivors was 11 years (range; 8-16 y) in CD3+/CD19+ group and 5 years (range; 2-9 y) in the TCRαβ+/CD19+ group.ResultsEngraftment kinetics were similar in both groups (13 days for neutrophils and 10 days for platelets). There was no difference in the incidence of acute GvHD II-IV (29 ± 5% in the CD3+/CD19+ group vs 38 ± 5% in the TCRαβ+/CD19+ group) and chronic GvHD (32 ± 5% vs 23 ± 4%, respectively). NRM was 23 ± 5% in the CD3+/CD19+group vs 21 ± 4% in the TCRαβ+/CD19+group. Relapse incidence was also similar, 32 ± 5% vs 34 ± 6%, respectively. DFS and OS were not different (45 ± 5% vs 45 ± 6% and 53 ± 6% vs 58 ± 6% respectively). As there were no differences on transplant outcomes between groups, we further analyzed all patients together for risk factors associated with transplant outcomes. On multivariate analysis, we identified that early disease status at transplant (HR: 0.16; 95%CI (0.07-0.35) (p=0.0001), presence of cGvHD (HR: 0.38; 95%CI (0.20-0.70) (p= 0.002), and donor KIR-B genotype (HR: 0.50; 95%CI (0.32-0.90) (p=0.04) were associated with better DFS.ConclusionsOur data suggest that there are no advantages in transplant outcomes between TCD platforms. Risk factors for survival are dependent on disease characteristic, donor KIR genotype, and chronic GvHD rather than the TCD platform used.

Abstract Background Telomeres are nucleoprotein structures present at the terminal region of the chromosomes. Mutations in genes coding for proteins involved in telomere maintenance are causative of a number of disorders known as telomeropathies. The genetic origin of these diseases is heterogeneous and has not been determined for a significant proportion of patients. Methods This article describes the genetic characterization of a cohort of patients. Telomere length was determined by Southern blot and quantitative PCR. Nucleotide variants were analyzed either by high-resolution melting analysis and Sanger sequencing of selected exons or by massive sequencing of a panel of genes. Results Forty-seven patients with telomere length below the 10% of normal population, affected with three telomeropathies: dyskeratosis congenita (4), aplastic anemia (22) or pulmonary fibrosis (21) were analyzed. Eighteen of these patients presented known pathogenic or novel possibly pathogenic variants in the telomere-related genes TERT, TERC, RTEL1, CTC1 and ACD. In addition, the analyses of a panel of 188 genes related to haematological disorders indicated that a relevant proportion of the patients (up to 35%) presented rare variants in genes related to DNA repair or in genes coding for proteins involved in the resolution of complex DNA structures, that participate in telomere replication. Mutations in some of these genes are causative of several syndromes previously associated to telomere shortening. Conclusion Novel variants in telomere, DNA repair and replication genes are described that might indicate the contribution of variants in these genes to the development of telomeropathies. Patients carrying variants in telomere-related genes presented worse evolution after diagnosis than the rest of patients analyzed.

Abstract Gene targeting constitutes a new step in the development of gene therapy for inherited diseases. Although previous studies have shown the feasibility of editing fibroblasts from Fanconi anemia (FA) patients, here we aimed at conducting therapeutic gene editing in clinically relevant cells, such as hematopoietic stem cells (HSCs). In our first experiments, we showed that zinc finger nuclease (ZFN)‐mediated insertion of a non‐therapeutic EGFP‐reporter donor in the AAVS1 “safe harbor” locus of FA‐A lymphoblastic cell lines (LCLs), indicating that FANCA is not essential for the editing of human cells. When the same approach was conducted with therapeutic FANCA donors, an efficient phenotypic correction of FA‐A LCLs was obtained. Using primary cord blood CD34+ cells from healthy donors, gene targeting was confirmed not only in in vitro cultured cells, but also in hematopoietic precursors responsible for the repopulation of primary and secondary immunodeficient mice. Moreover, when similar experiments were conducted with mobilized peripheral blood CD34+ cells from FA‐A patients, we could demonstrate for the first time that gene targeting in primary hematopoietic precursors from FA patients is feasible and compatible with the phenotypic correction of these clinically relevant cells.

We prospectively analyzed outcomes of haploidentical hematopoietic stem cell transplantation using αβ+ T-cell receptor/CD19+ depleted grafts. Sixty-three transplantations were performed in 60 patients. Twenty-eight patients were diagnosed with acute lymphoblastic leukemia (ALL), 27 patients were diagnosed with acute myelogenous leukemia, and in eight other hematological malignancies were diagnosed. Twenty-three were in first complete remission (CR), 20 in second CR, 20 beyond second CR. Four patients developed graft failure. Median time to neutrophil and platelet recovery was 14 (range 9–25) and 10 days (range 7–30), respectively. The probability of non-relapse mortality (NRM) by day +100 after transplantation was 10 ± 4%. With a median follow-up of 28 months, the probability of relapse was 32 ± 6% and disease-free survival was 52 ± 6%. Immune reconstitution was leaded by NK cells. As such, a high CD56dim/CD56bright NK cell ratio early after transplantation was associated with better disease-free survival (DFS) (≥3.5; 77 ± 8% vs.

Pyruvate kinase deficiency (PKD) is a rare erythroid metabolic disease caused by mutations in the PKLR gene. Erythrocytes from PKD patients show an energetic imbalance causing chronic non-spherocytic hemolytic anemia, as pyruvate kinase defects impair ATP production in erythrocytes. We generated PKD induced pluripotent stem cells (PKDiPSCs) from peripheral blood mononuclear cells (PB-MNCs) of PKD patients by non-integrative Sendai viral vectors. PKDiPSCs were gene edited to integrate a partial codon-optimized R-type pyruvate kinase cDNA in the second intron of the PKLR gene by TALEN-mediated homologous recombination (HR). Notably, we found allele specificity of HR led by the presence of a single-nucleotide polymorphism. High numbers of erythroid cells derived from gene-edited PKDiPSCs showed correction of the energetic imbalance, providing an approach to correct metabolic erythroid diseases and demonstrating the practicality of this approach to generate the large cell numbers required for comprehensive biochemical and metabolic erythroid analyses.

Background Congenital sideroblastic anemias are rare disorders with several genetic causes; they are characterized by erythroblast mitochondrial iron overload, differ greatly in severity and some occur within a syndrome. The most common cause of non-syndromic, microcytic sideroblastic anemia is a defect in the X-linked 5-aminolevulinate synthase 2 gene but this is not always present. Recently, variations in the gene for the mitochondrial carrier SLC25A38 were reported to cause a non-syndromic, severe type of autosomal-recessive sideroblastic anemia. Further evaluation of the importance of this gene was required to estimate the proportion of patients affected and to gain further insight into the range and types of variations involved.Design and Methods In three European diagnostic laboratories sequence analysis of SLC25A38 was performed on DNA from patients affected by congenital sideroblastic anemia of a non-syndromic nature not caused by variations in the 5-aminolevulinate synthase 2 gene.Results Eleven patients whose ancestral origins spread across several continents were homozygous or compound heterozygous for ten different SLC25A38 variations causing premature termination of translation (p.Arg117X, p.Tyr109LeufsX43), predicted splicing alteration (c.625G>C; p.Asp209His) or missense substitution (p.Gln56Lys, p.Arg134Cys, p.Ile147Asn, p.Arg187Gln, p.Pro190Arg, p.Gly228Val, p.Arg278Gly). Only three of these variations have been described previously (p.Arg117X, p.Tyr109LeufsX43 and p.Asp209His). All new variants reported here are missense and affect conserved amino acids. Structure modeling suggests that these variants may influence different aspects of transport as described for mutations in other mitochondrial carrier disorders.Conclusions Mutations in the SLC25A38 gene cause severe, non-syndromic, microcytic/hypochromic sideroblastic anemia in many populations. Missense mutations are shown to be of importance as are mutations that affect protein production. Further investigation of these mutations should shed light on structure-function relationships in this protein.

IntroductionEnrolling children with cancer in early phase trials is crucial to access innovative treatments, contributing to advancing pediatric oncology research and providing tailored therapeutic options. Our objective is to analyze the impact of these trials on patient outcomes and safety, and to examine the evolution and feasibility of trials in pediatric cancer over the past decade.MethodsAll patients recruited in pediatric anticancer phase I/II clinical trials from January 2014 to December 2022 were included. Clinical records and trial protocols were analyzed.ResultsA total of 215 patients (median age 11.2 years, range 1–29.5) were included in 52 trials (258 inclusions). Patients with extracranial solid tumors (67%), central nervous system (CNS) tumors (24%), and leukemia (9%) were included. The most common investigational drugs were small molecules (28.3%) and antibodies (20.5%). Serious adverse events were experienced by 41% of patients, 4.4% discontinued treatment because of toxicity and two had toxic deaths. Median event-free survival was 3.7 months (95%CI: 2.8–4.5), longer in phase II trials than in phase I (2 vs. 6.3 months; p ≤ 0.001). Median overall survival was 12 months (95%CI: 9–15), higher in target-specific vs. non-target-specific trials (14 vs. 6 months; p ≤ 0.001).DiscussionA significant and increasing number of patients have been included in early clinical trials, suggesting that both oncologists and families consider it valuable to be referred to specialized Units to access new therapies. Moreover, our data suggests that participation in early clinical trials, although not without potential toxicities, might have a positive impact on individual outcomes.

IntroductionFanconi anemia (FA) is a genomic instability disorder associated with congenital abnormalities, including short stature and the presence of central nervous system anomalies, especially in the hypothalamic-pituitary area. Thus, differences in pituitary size could associate with the short stature observed in these patients. Our aim was to evaluate whether central nervous system abnormalities and pituitary gland volume correlate with height and hormone deficiencies in these patients.MethodsIn this cross-sectional exploratory study 21 patients diagnosed with FA between 2017 and 2022 in a Spanish Reference Center were investigated. Magnetic resonance imaging (MRI) was performed and pituitary volume calculated and corelated with height and other endocrine parameters.ResultsThe percentage of abnormalities in our series was 81%, with a small pituitary (pituitary volume less than 1 SD) being the most frequent, followed by Chiari malformation type 1. The median value of pituitary volume was -1.03 SD (IQR: -1.56, -0.36). Short stature was found in 66.7% [CI95% 43-85.4]. Total volume (mm3) increases significantly with age and in pubertal stages. There were no differences between volume SD and pubertal stage, or the presence of endocrine deficiencies. No correlations were found between pituitary volume and the presence of short stature. The intraclass correlation index (ICC) average for volume was 0.85 [CI95% 0.61-0.94] indicating a good‐to‐excellent correlation of measurements.DiscussionCentral nervous system anomalies are part of the FA phenotype, the most frequent after pituitary hypoplasia being posterior fossa abnormalities, which may have clinical repercussions in the patient. It is therefore necessary to identify those who could be candidates for neurosurgical intervention. The size of the pituitary gland is smaller in these patients, but this does not seem to be related to hormone deficiency and short stature or exposure to a low dose of total body irradiation.

IntroductionFanconi anemia (FA) is an inherited disorder characterized by bone marrow failure, congenital malformations, and predisposition to malignancies. Alterations in hematopoietic stem cells (HSC) have been reported, but little is known regarding the bone marrow (BM) stroma. Thus, the characterization of Mesenchymal Stromal Cells (MSC) would help to elucidate their involvement in the BM failure.MethodsWe characterized MSCs of 28 FA patients (FA-MSC) before and after treatment (hematopoietic stem cell transplantation, HSCT; or gene therapy, GT). Phenotypic and functional properties were analyzed and compared with MSCs expanded from 26 healthy donors (HD-MSCs). FA-MSCs were genetically characterized through, mitomycin C-test and chimerism analysis. Furthermore, RNA-seq profiling was used to identify dysregulated metabolic pathways.ResultsOverall, FA-MSC had the same phenotypic and functional characteristics as HD-MSC. Of note, MSC-GT had a lower clonogenic efficiency. These findings were not confirmed in the whole FA patients’ cohort. Transcriptomic profiling identified dysregulation in HSC self-maintenance pathways in FA-MSC (HOX), and was confirmed by real-time quantitative polymerase chain reaction (RT-qPCR).DiscussionOur study provides a comprehensive characterization of FA-MSCs, including for the first time MSC-GT and constitutes the largest series published to date. Interestingly, transcript profiling revealed dysregulation of metabolic pathways related to HSC self-maintenance. Taken together, our results or findings provide new insights into the pathophysiology of the disease, although whether these niche defects are involved in the hematopoietic defects seen of FA deserves further investigation.

Leukocyte adhesion deficiency type I (LAD-I) is a primary immunodeficiency caused by mutations in the ITGB2 gene, which encodes for the CD18 subunit of β2-integrins. Deficient expression of β2-integrins results in impaired neutrophil migration in response to bacterial and fungal infections. Using a lentiviral vector (LV) that mediates a preferential myeloid expression of human CD18 (Chim.hCD18-LV), we first demonstrated that gene therapy efficiently corrected the phenotype of mice with severe LAD-I. Next, we investigated if the ectopic hCD18 expression modified the phenotypic characteristics of human healthy donor hematopoietic stem cells and their progeny. Significantly, transduction of healthy CD34+ cells with the Chim.hCD18-LV did not modify the membrane expression of CD18 nor the adhesion of physiological ligands to transduced cells. Additionally, we observed that the repopulating properties of healthy CD34+ cells were preserved following transduction with the Chim.hCD18-LV, and that a safe polyclonal repopulation pattern was observed in transplanted immunodeficient NOD scid gamma (NSG) mice. In a final set of experiments, we demonstrated that transduction of CD34+ cells from a severe LAD-I patient with the Chim.hCD18-LV restores the expression of β2-integrins in these cells. These results offer additional preclinical safety and efficacy evidence supporting the gene therapy of patients with severe LAD-I.

Abstract The screening of the BCR::ABL1 kinase domain (KD) mutation has become a routine analysis in case of warning/failure for chronic myeloid leukemia (CML) and B-cell precursor acute lymphoblastic leukemia (ALL) Philadelphia (Ph)-positive patients. In this study, we present a novel DNA-based next-generation sequencing (NGS) methodology for KD ABL1 mutation detection and monitoring with a 1.0E−4 sensitivity. This approach was validated with a well-stablished RNA-based nested NGS method. The correlation of both techniques for the quantification of ABL1 mutations was high (Pearson r = 0.858, p

IntroductionThe use of peripheral blood progenitor cells (PBPCs) as a source for hematopoietic stem cell transplantation (HSCT) in pediatric healthy donors is still under debate. The risk of a central venous catheter (CVC) placement and catheter-related complications continue to be the main arguments to discourage its use.Methodswe present a retrospective analysis of 140 PBPC collections in pediatric patients and donors, describing adverse events (AE) related to CVCs as well as the influence of catheterrelated variables on the efficiency of the leukapheresis.Results14 CVC-related AEs were recorded (10%). The most common was fever in 5 patients, 4 of which had a catheter-related bacteriemia. Thrombotic events were only observed in 3 patients with active malignancy. A healthy donor presented a moderate bleeding after catheter withdrawal that resolved with local measures, and none of the rest presented any AE. Regarding variables related to the development of AEs, the subject group (patient or donor) was the only one significantly associated (p

Clinical trials have shown that lentiviral-mediated gene therapy can ameliorate bone marrow failure (BMF) in nonconditioned Fanconi anemia (FA) patients resulting from the proliferative advantage of corrected FA hematopoietic stem and progenitor cells (HSPC). However, it is not yet known if gene therapy can revert affected molecular pathways in diseased HSPC. Single-cell RNA sequencing was performed in chimeric populations of corrected and uncorrected HSPC co-existing in the BM of gene therapy-treated FA patients. Our study demonstrates that gene therapy reverts the transcriptional signature of FA HSPC, which then resemble the transcriptional program of healthy donor HSPC. This includes a down-regulated expression of TGF-β and p21, typically up-regulated in FA HSPC, and upregulation of DNA damage response and telomere maintenance pathways. Our results show for the first time the potential of gene therapy to rescue defects in the HSPC transcriptional program from patients with inherited diseases; in this case, in FA characterized by BMF and cancer predisposition.

Difficulties in the collection of hematopoietic stem and progenitor cells (HSPCs) from Fanconi anemia (FA) patients have limited the gene therapy in this disease. We have investigated (ClinicalTrials.gov, NCT02931071) the safety and efficacy of filgrastim and plerixafor for mobilization of HSPCs and collection by leukapheresis in FA patients. Nine of eleven enrolled patients mobilized beyond the threshold level of 5 CD34+ cells/μL required to initiate apheresis. A median of 21.8 CD34+ cells/μL was reached at the peak of mobilization. Significantly, the oldest patients (15 and 16 years old) were the only ones who did not reach that threshold. A median of 4.27 million CD34+ cells/kg was collected in 2 or 3 aphereses. These numbers were markedly decreased to 1.1 million CD34+ cells/kg after immunoselection, probably because of weak expression of the CD34 antigen. However, these numbers were sufficient to facilitate the engraftment of corrected HSPCs in non-conditioned patients. No procedure-associated serious adverse events were observed. Mobilization of CD34+ cells correlated with younger age, higher leukocyte counts and hemoglobin values, lower mean corpuscular volume, and higher proportion of CD34+ cells in bone marrow (BM). All these values offer crucial information for the enrollment of FA patients for gene therapy protocols.

Introduction: In recent years, there have been changes in the management of patients with primary immune thrombocytopenia. In this study, a review is presented of the characteristics and outcomes of children with primary immune thrombocytopenia in a children’s hospital (Hospital Infantil Niño Jesús). Moreover, an analysis is made of the changes in the care of these patients diagnosed before and after 2011, when new guidelines were published by the Spanish Society of Paediatric Haematology Oncology (SEHOP). Material and methods: Data from a cohort of primary immune thrombocytopenia patients followed up in this hospital have been retrospectively reviewed. The statistical package used for the analysis was SPSS Statistics 22.0 (IBM Corp., Chicago, IL, USA). Results: A review is presented on the clinical data from 235 paediatric patients diagnosed with primary immune thrombocytopenia. It was observed that some features at diagnosis, such as age younger than five years and a previous history of infection, influenced the probability of cure. Regarding the changes in the management of patients since 2011, the steroid doses received during the first month and the first year, and the number of days corresponding to the patient’s first admission have both significantly decreased. Splenectomies were also significantly reduced. Conclusions: Since 2011, there have been changes in the medical care of our primary immune thrombocytopenia patients: they receive lower doses of steroids, they stay fewer days in the hospital, and the number of splenectomies has decreased without increasing bleeding or worsening the clinical evolution. Furthermore, it was observed that age younger than 5 years and a history of infection prior to diagnosis were related to higher chances of recovery. Resumen: Introducción: En los últimos años se han experimentado cambios en el manejo de los pacientes con trombocitopenia inmune primaria. En este estudio se revisan las características de los pacientes con trombocitopenia inmune primaria del Hospital Infantil Universitario Niño Jesús y su evolución. Además, analizamos los cambios en el abordaje de los pacientes diagnosticados antes y después del 2011, año en el que se publicó la guía de la Sociedad Española de Pediatría. Material y métodos: Se han revisado retrospectivamente los datos de pacientes con trombocitopenia inmune primaria en seguimiento en nuestro hospital desde el año 2000. El paquete estadístico utilizado para el análisis fue SPSS Statistics 22.0 (IBM Corp, Chicago, IL, EE.UU.). Resultados: Se han revisado 235 pacientes pediátricos con trombocitopenia inmune primaria observando que algunas características al diagnóstico, como la edad menor de 5 años y los antecedentes previos de infección, pueden influir en la probabilidad de recuperación. Con respecto al cambio de manejo de los pacientes, a partir de 2011 las dosis de esteroides recibidas durante el primer mes y el primer año se han reducido de forma significativa, así como el número de días del primer ingreso pasando de 5 a 3 días. Las esplenectomías también se han reducido significativamente. Conclusiones: Desde el año 2011 se han producido cambios en el abordaje de nuestros pacientes: reciben una menor dosis de esteroides, permanecen menos días ingresados y se ha reducido el número de esplenectomías sin aumentar los sangrados y sin disminuir la tasa de respuestas. Además, observamos que la edad menor de 5 años y el antecedente de infección previa al diagnóstico están relacionados con una mayor tasa de recuperación.

Resumen: Introducción: En los últimos años se han experimentado cambios en el manejo de los pacientes con trombocitopenia inmune primaria. En este estudio se revisan las características de los pacientes con trombocitopenia inmune primaria del Hospital Infantil Universitario Niño Jesús y su evolución. Además, analizamos los cambios en el abordaje de los pacientes diagnosticados antes y después de 2011, año en el que se publicó la guía de la Sociedad Española de Pediatría. Material y métodos: Se han revisado retrospectivamente los datos de pacientes con trombocitopenia inmune primaria en seguimiento en nuestro hospital desde el año 2000. El paquete estadístico utilizado para el análisis fue SPSS Statistics 22.0 (IBM Corp, Chicago, IL, EE.UU.). Resultados: Se han revisado 235 pacientes pediátricos con trombocitopenia inmune primaria, observando que algunas características al diagnóstico, como la edad menor de 5 años y los antecedentes previos de infección, pueden influir en la probabilidad de recuperación. Con respecto al cambio de manejo de los pacientes, a partir de 2011 las dosis de esteroides recibidas durante el primer mes y el primer año se han reducido de forma significativa, así como el número de días del primer ingreso, pasando de 5 a 3 días. Las esplenectomías también se han reducido significativamente. Conclusiones: Desde el año 2011 se han producido cambios en el abordaje de nuestros pacientes: reciben una menor dosis de esteroides, permanecen menos días ingresados y se ha reducido el número de esplenectomías sin aumentar los sangrados y sin disminuir la tasa de respuestas. Además, observamos que la edad menor de 5 años y el antecedente de infección previa al diagnóstico están relacionados con una mayor tasa de recuperación. Abstract: Introduction: In recent years, there have been changes in the management of patients with primary immune thrombocytopenia. In this study, a review is presented of the characteristics and outcomes of children with primary immune thrombocytopenia in a children's hospital (Hospital Infantil Niño Jesús, Madrid, Spain). Moreover, an analysis is made of the changes in the care of these patients diagnosed before and after 2011, when new guidelines were published by the Spanish Society of Paediatric Haematology Oncology (SEHOP). Material and methods: Data from a cohort of primary immune thrombocytopenia patients followed up in this hospital have been retrospectively reviewed. The statistical package used for the analysis was SPSS Statistics 22.0 (IBM Corp, Chicago, IL, USA). Results: A review is presented on the clinical data from 235 paediatric patients diagnosed with primary immune thrombocytopenia. It was observed that some features at diagnosis, such as age younger than 5 years and a previous history of infection, influenced the probability of cure. Regarding the changes in the management of patients since 2011, the steroid doses received during the first month and the first year, and the number of days corresponding to the patient's first admission have both significantly decreased. Splenectomies were also significantly reduced. Conclusions: Since 2011, there have been changes in the medical care of our primary immune thrombocytopenia patients: they receive lower doses of steroids, they stay fewer days in the hospital, and the number of splenectomies has decreased without increasing bleeding or worsening the clinical evolution. Furthermore, it was observed that age younger than 5 years and a history of infection prior to diagnosis were related to higher chances of recovery.

Resumen: Introducción: La anemia hemolítica autoinmune (AHAI) es una enfermedad rara en niños, generalmente autolimitada. Material y métodos: Estudio descriptivo transversal en menores de 18 años diagnosticados de AHAI desde enero de 1997 a julio de 2019. Se recogieron variables clínicas y se clasificaron según el test de Coombs directo (TCD) en AHAI por anticuerpos calientes (IgG+/-C3d) y fríos (C3d). Se analizó la respuesta al tratamiento y su evolución. Resultados: Se incluyeron 25 pacientes, siendo el 72% varones. La media de edad al diagnóstico fue de dos años (rango 0,4-9). Los síntomas predominantes fueron fiebre (72%), palidez (68%), ictericia (64%), hepatoesplenomegalia y coluria (48%). La mediana de hemoglobina al diagnóstico fue 5,4 g/dL. En el 96% el TCD fue positivo, con detección de anticuerpos IgG en el 76%. Un solo caso presentó TCD negativo. Un 20% asociaron otra citopenia, uno de ellos fue diagnosticado posteriormente de inmunodeficiencia variable común. En un 32% se sospechó o documentó una infección viral concomitante. La mayoría de los casos fueron autolimitados y respondieron a tratamiento con corticoides (72%). Aquellos con respuesta parcial (24%), principalmente los que asociaban otras citopenias, precisaron otras líneas de tratamiento (rituximab, micofenolato, inmunoglobulinas). Se detectaron complicaciones (32%) y recaídas (26%) únicamente en AHAI por anticuerpos calientes. Conclusiones: Nuestra serie confirma que la AHAI es una enfermedad muy poco frecuente en la infancia. La mayoría de los casos evolucionan favorablemente, aunque hasta una cuarta parte precisan segundas líneas de tratamiento y casos excepcionales tratamientos muy agresivos. Estos últimos suelen corresponder a pacientes con más de una citopenia en la evolución de la enfermedad. Abstract: Introduction: Autoimmune hemolytic anemia (AIHA) is a rare and generally self-limiting disease in children. Material and methods: A descriptive cross-sectional study was performed in children under 18 years diagnosed with AIHA from January/1997 to July/2019. Clinical variables were collected and AIHA was classified according to the direct antiglobulin test (DAT) in warm AIHA (IgG+/-C3d) and cold AIHA (C3d). Response to treatment and evolution were analyzed. Results: 25 patients were included and 72% were males. The median age at diagnosis was 2 years (range 0.4 to 9). Fever (72%), pallor (68%), jaundice (64%), hepatosplenomegaly and coluria (48%) were the most common presenting symptoms. The median hemoglobin at diagnosis was 5.4 g/dl. DAT was positive in 96%, with detection of IgG antibodies in 76%. A single case presented negative DAT. 20% of the patients associated another cytopenia, one of which was subsequently diagnosed with common variable immunodeficiency. Concomitant viral infection was suspected or documented in 32%. Most of the cases were self-limiting and responded to corticosteroid treatment (72%). Those with partial response (24%), mainly those associated with other cytopenias, required other lines of treatment (rituximab, mycophenolate, immunoglobulins). Complications (32%) and relapses (26%) were detected only in warm AIHA. Conclusions: Our case series confirms that AIHA is a very rare disease in childhood. Most cases evolve favorably, although up to a quarter of them require second lines of treatment and, in exceptional cases, they need very aggressive treatments. These latter cases generally correspond to patients who present more than one cytopenia in the course of the disease.

Introduction: Autoimmune hemolytic anemia (AIHA) is a rare and generally self-limiting disease in children. Material and methods: A descriptive cross-sectional study was performed in children under 18 years diagnosed with AIHA from January 1997 to July 2019. Clinical variables were collected and AIHA was classified according to the direct antiglobulin test (DAT) in warm AIHA (IgG+/-C3d) and cold AIHA (C3d). Response to treatment and evolution were analyzed. Results: 25 patients were included and 72% were males. The median age at diagnosis was 2 years (range 0.4–9). Fever (72%), pallor (68%), jaundice (64%), hepatosplenomegaly and coluria (48%) were the most common presenting symptoms. The median hemoglobin at diagnosis was 5.4 g/dl. DAT was positive in 96%, with detection of IgG antibodies in 76%. A single case presented negative DAT. 20% of the patients associated another cytopenia, one of which was subsequently diagnosed with common variable immunodeficiency. Concomitant viral infection was suspected or documented in 32%. Most of the cases were self-limiting and responded to corticosteroid treatment (72%). Those with partial response (24%), mainly those associated with other cytopenias, required other lines of treatment (rituximab, mycophenolate, immunoglobulins,…). Complications (32%) and relapses (26%) were detected only in warm AIHA. Conclusions: Our case series confirms that AIHA is a very rare disease in childhood. Most cases evolve favorably, although up to a quarter of them require second lines of treatment and, in exceptional cases, they need very aggressive treatments. These latter cases generally correspond to patients who present more than one cytopenia in the course of the disease. Resumen: Introducción: La anemia hemolítica autoinmune (AHAI) es una enfermedad rara en niños, generalmente autolimitada. Material y métodos: Estudio descriptivo transversal en menores de 18 años diagnosticados de AHAI desde enero 1997 a julio 2019. Se recogieron variables clínicas y se clasificaron según el test de Coombs directo (TCD) en AHAI por anticuerpos calientes (IgG+/-C3d) y fríos (C3d). Se analizó la respuesta al tratamiento y su evolución. Resultados: Se incluyeron 25 pacientes, siendo el 72% varones. La mediada de edad al diagnóstico fue 2 años (rango 0,4–9). Los síntomas predominantes fueron fiebre (72%), palidez (68%), ictericia (64%), hepatoesplenomegalia y coluria (48%). La mediana de hemoglobina al diagnóstico fue 5,4 gr/dl. En el 96% el TCD fue positivo, con detección de anticuerpos IgG en el 76%. Un solo caso presentó TCD negativo. Un 20% asociaron otra citopenia, uno de ellos fue diagnosticado posteriormente de inmunodeficiencia variable común. En un 32% se sospechó o documentó una infección viral concomitante. La mayoría de los casos fueron autolimitados y respondieron a tratamiento con corticoides (72%). Aquellos con respuesta parcial (24%), principalmente los que asociaban otras citopenias, precisaron otras líneas de tratamiento (rituximab, micofenolato, inmunoglobulinas,…). Se detectaron complicaciones (32%) y recaídas (26%) únicamente en AHAI por anticuerpos calientes. Conclusiones: Nuestra serie confirma que la AHAI es una enfermedad muy poco frecuente en la infancia. La mayoría de los casos evolucionan favorablemente, aunque hasta una cuarta parte precisan segundas líneas de tratamiento y casos excepcionales tratamientos muy agresivos. Estos últimos suelen corresponder a pacientes con más de una citopenia en la evolución de la enfermedad.

Fanconi anemia (FA) is the most prevalent inherited bone marrow failure (BMF) syndrome. Nevertheless, the pathophysiological mechanisms of BMF in FA have not been fully elucidated. Since FA cells are defective in DNA repair, we hypothesized that FA hematopoietic stem and progenitor cells (HSPCs) might express DNA damage–associated stress molecules such as natural killer group 2 member D ligands (NKG2D-Ls). These ligands could then interact with the activating NKG2D receptor expressed in cytotoxic NK or CD8+ T cells, which may result in progressive HSPC depletion. Our results indeed demonstrated upregulated levels of NKG2D-Ls in cultured FA fibroblasts and T cells, and these levels were further exacerbated by mitomycin C or formaldehyde. Notably, a high proportion of BM CD34+ HSPCs from patients with FA also expressed increased levels of NKG2D-Ls, which correlated inversely with the percentage of CD34+ cells in BM. Remarkably, the reduced clonogenic potential characteristic of FA HSPCs was improved by blocking NKG2D–NKG2D-L interactions. Moreover, the in vivo blockage of these interactions in a BMF FA mouse model ameliorated the anemia in these animals. Our study demonstrates the involvement of NKG2D–NKG2D-L interactions in FA HSPC functionality, suggesting an unexpected role of the immune system in the progressive BMF that is characteristic of FA.

Inherited bone marrow failure syndromes (IBMFSs) are a group of congenital rare diseases characterized by bone marrow failure, congenital anomalies, high genetic heterogeneity, and predisposition to cancer. Appropriate treatment and cancer surveillance ideally depend on the identification of the mutated gene. A next-generation sequencing (NGS) panel of genes could be 1 initial genetic screening test to be carried out in a comprehensive study of IBMFSs, allowing molecular detection in affected patients. We designed 2 NGS panels of IBMFS genes: version 1 included 129 genes and version 2 involved 145 genes. The cohort included a total of 204 patients with suspected IBMFSs without molecular diagnosis. Capture-based targeted sequencing covered > 99% of the target regions of 145 genes, with more than 20 independent reads. No differences were seen between the 2 versions of the panel. The NGS tool allowed a total of 91 patients to be diagnosed, with an overall molecular diagnostic rate of 44%. Among the 167 patients with classified IBMFSs, 81 patients (48%) were diagnosed. Unclassified IBMFSs involved a total of 37 patients, of whom 9 patients (24%) were diagnosed. The preexisting diagnosis of 6 clinically classified patients (6%) was amended, implying a change of therapy for some of them. Our NGS IBMFS gene panel assay is a useful tool in the molecular diagnosis of IBMFSs and a reasonable option as the first tier genetic test in these disorders.

Abstract: Detectable clonal mosaicism for large chromosomal events has been associated with aging and an increased risk of hematological and some solid cancers. We hypothesized that genetic cancer predisposition disorders, such as Fanconi anemia (FA), could manifest a high rate of chromosomal mosaic events (CMEs) in peripheral blood, which could be used as early biomarkers of cancer risk. We studied the prevalence of CMEs by single-nucleotide polymorphism (SNP) array in 130 FA patients' blood DNA and their impact on cancer risk. We detected 51 CMEs (4.4-159 Mb in size) in 16 out of 130 patients (12.3%), of which 9 had multiple CMEs. The most frequent events were gains at 3q (n = 6) and 1q (n = 5), both previously associated with leukemia, as well as rearrangements with breakpoint clustering within the major histocompatibility complex locus (P = 7.3 × 10−9). Compared with 15 743 age-matched population controls, FA patients had a 126 to 140 times higher risk of detectable CMEs in blood (P < 2.2 × 10−16). Prevalent and incident hematologic and solid cancers were more common in CME carriers (odds ratio [OR] = 11.6, 95% confidence interval [CI] = 3.4-39.3, P = 2.8 × 10−5), leading to poorer prognosis. The age-adjusted hazard risk (HR) of having cancer was almost 5 times higher in FA individuals with CMEs than in those without CMEs. Regarding survival, the HR of dying was 4 times higher in FA individuals having CMEs (HR = 4.0, 95% CI = 2.0-7.9, P = 5.7 × 10−5). Therefore, our data suggest that molecular karyotyping with SNP arrays in easy-to-obtain blood samples could be used for better monitoring of bone marrow clonal events, cancer risk, and overall survival of FA patients.

CRISPR/Cas9 allows the generation of knockout cell lines and null zygotes by inducing site-specific double-stranded breaks. In most cases the DSB is repaired by non-homologous end joining, resulting in small nucleotide insertions or deletions that can be used to construct knockout alleles. However, these mutations do not produce the desired null result in all cases, but instead generate a similar, functionally active protein. This effect could limit the therapeutic efficiency of gene therapy strategies based on abrogating oncogene expression, and therefore needs to be considered carefully. If there is an acceptable degree of efficiency of CRISPR/Cas9 delivery to cells, the key step for success lies in the effectiveness of a specific sgRNA at knocking out the oncogene, when only one sgRNA can be used. This study shows that the null effect could be increased with an sgRNA targeting the splice donor site (SDS) of the chosen exon. Following this strategy, the generation of null alleles would be facilitated in two independent ways: the probability of producing a frameshift mutation and the probability of interrupting the canonical mechanism of pre-mRNA splicing. In these contexts, we propose to improve the loss-of-function yield driving the CRISPR system at the SDS of critical exons.

Las anemias raras y los fallos medulares hereditarios son enfermedades hematológicas caracterizadas, respectivamente, por una disminución de la concentración de hemoglobina o por diversos grados de defectos en la producción de células hematopoyéticas que conducen desde una citopenia de un solo linaje hasta una de múltiples linajes. Son enfermedades raras y difíciles de diagnosticar debido a la heterogeneidad clínica, citológica y genética. En este artículo abordaremos en primer lugar el diagnóstico de las anemias raras y sus causas principales: fallos medulares, defectos del hematíe y trastornos del metabolismo de los factores de maduración eritrocitario. Seguidamente introduciremos los fallos medulares hereditarios y su patología asociada, como son las malformaciones congénitas y la predisposición tumoral, haciendo especial hincapié en los más frecuentes: la anemia de Fanconi, la disqueratosis congénitca, la anemia de Diamond-Blackfan y el síndrome de Shwachman-Diamond.