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The t(2;11)(q31;p15) chromosomal translocation results in a fusion between the NUP98 and HOXD13 genes and has been observed in patients with myelodysplastic syndrome (MDS) or acute myelogenous leukemia. We previously showed that expression of the NUP98-HOXD13 (NHD13) fusion gene in transgenic mice results in an invariably fatal MDS; approximately one third of mice die due to complications of severe pancytopenia, and about two thirds progress to a fatal acute leukemia. In the present study, we used retroviral insertional mutagenesis to identify genes that might collaborate with NHD13 as the MDS transformed to an acute leukemia. Newborn NHD13 transgenic mice and littermate controls were infected with the MOL4070LTR retrovirus. The onset of leukemia was accelerated, suggesting a synergistic effect between the NHD13 transgene and the genes neighboring retroviral insertion events. We identified numerous common insertion sites located near protein-coding genes and confirmed dysregulation of a subset of these by expression analyses. Among these genes were Meis1, a known collaborator of HOX and NUP98-HOX fusion genes, and Mn1, a transcriptional coactivator involved in human leukemia through fusion with the TEL gene. Other putative collaborators included Gata2, Erg, and Epor. Of note, we identified a common insertion site that was >100 kb from the nearest coding gene, but within 20 kb of the miR29a/miR29b1 microRNA locus. Both of these miRNA were up-regulated, demonstrating that retroviral insertional mutagenesis can target miRNA loci as well as protein-coding loci. Our data provide new insights into NHD13-mediated leukemogenesis as well as retroviral insertional mutagenesis mechanisms. [Cancer Res 2007;67(11):5148–55]

Fanconi anemia (FA), a genetic DNA repair disorder characterized by marrow failure and cancer susceptibility. In FA mice, metformin improves blood counts and delays tumor development. We conducted a single institution study of metformin in nondiabetic patients with FA to determine feasibility and tolerability of metformin treatment and to assess for improvement in blood counts. Fourteen of 15 patients with at least 1 cytopenia (hemoglobin < 10 g/dL; platelet count < 100 000 cells/µL; or an absolute neutrophil count < 1000 cells/µL) were eligible to receive metformin for 6 months. Median patient age was 9.4 years (range 6.0-26.5 ). Thirteen of 14 subjects (93%) tolerated maximal dosing for age; 1 subject had dose reduction for grade 2 gastrointestinal symptoms. No subjects developed hypoglycemia or metabolic acidosis. No subjects had dose interruptions caused by toxicity, and no grade 3 or higher adverse events attributed to metformin were observed. Hematologic response based on modified Myelodysplastic Syndrome International Working Group criteria was observed in 4 of 13 evaluable patients (30.8%; 90% confidence interval, 11.3-57.3). Median time to response was 84.5 days (range 71-128 days). Responses were noted in neutrophils (n = 3), platelets (n = 1), and red blood cells (n = 1). No subjects met criteria for disease progression or relapse during treatment. Correlative studies explored potential mechanisms of metformin activity in FA. Plasma proteomics showed reduction in inflammatory pathways with metformin. Metformin is safe and tolerable in nondiabetic patients with FA and may provide therapeutic benefit. This trial was registered at as #NCT03398824.

To determine the optimal MRI protocol and sequences for liver and cardiac iron estimation in children.We evaluated patients ≤18 years with cardiac and liver MRIs for iron content estimation. Liver T2 was determined by a third-party company. Cardiac and Liver T2* values were measured by an observer. Liver T2* values were calculated using the available liver parenchyma in the cardiac MRI. Linear correlations and Bland-Altman plots were run between liver T2 and T2*, cardiac T2* values; and liver T2* on dedicated cardiac and liver MRIs.139 patients were included. Mean liver T2 and T2* values were 8.6 ± 5.4 ms and 4.5 ± 4.1 ms, respectively. A strong correlation between liver T2 and T2* values was observed (r = 0.96, p 0.001) with a bias (+4.1 ms). Mean cardiac bright- and dark-blood T2* values were 26.5 ± 12.9 ms and 27.2 ± 11.9 ms, respectively. Cardiac T2* values showed a strong correlation (r = 0.81, p 0.001) with a low bias (-1.0 ms). The mean liver T2* on liver and cardiac MRIs were 4.9 ± 4.7 ms and 4.6 ± 3.9 ms, respectively. A strong correlation between T2* values was observed (r = 0.96, p 0.001) with a small bias (-0.2 ms).MRI protocols for iron concentration in the liver and the heart can be simplified to avoid redundant information and reduce scan time. In most patients, a single breath-hold GRE sequence can be used to evaluate the iron concentration in both the liver and heart.

Problem There is a clear and urgent need for health care innovation in the United States. Hospital employees routinely recognize pain points that affect care delivery and are in a unique position to propose innovative and practical solutions, yet leaders rarely solicit ideas for investment and development from frontline providers and staff, revealing an untapped resource with innovation potential. Approach To address these deficiencies, the Children's Hospital of Philadelphia (CHOP) expanded its innovation infrastructure with the competition-based SPRINT program in 2015. All hospital employees are encouraged to apply with early stage innovative ideas, and if selected, are provided with business, legal, technical, and scientific project management support to help accelerate their projects toward commercial viability. SPRINT was modeled around 4 core tenets: (1) small, dynamic, and attentive project manager-led teams; (2) low barriers to entry; (3) emphasis on outreach; and (4) fostering innovators. Outcomes Over its first 4 cycles from 2015 to 2018, 271 innovative teams applied to the SPRINT program, which led to support for 30 projects (11% acceptance rate). About a quarter of the projects each year were submitted by physician-led teams (mean 23%), a third by non-physician clinical providers (mean 33%), and almost half were submitted by employees without direct patient contact (mean 44%). Nurses have emerged as the largest applicant group. Eleven of the SPRINT supported projects (37%) resulted in commercial endpoints. Next steps SPRINT has proven to be an effective model for supporting institution-wide, employee-driven health care innovation, especially among frontline clinical and non-clinical personnel. Critical next steps for the program include a formal cost-benefit analysis and the earlier participation of technology transfer and intellectual property experts to improve the commercialization roadmap for many SPRINT projects.

Background Diamond-Blackfan anemia (DBA) is an inherited bone marrow failure syndrome characterized by anemia, short stature, congenital anomalies, and cancer predisposition. Most cases are due to mutations in genes encoding ribosomal proteins (RP) leading to RP haploinsufficiency. Effective treatments for the anemia of DBA include chronic red cell transfusions, long-term corticosteroid therapy, or hematopoietic stem cell transplantation. In a small patient series and in animal models, there have been hematologic responses to L-leucine with amelioration of anemia. The study objectives of this clinical trial were to determine feasibility, safety, and efficacy of L-leucine in transfusion-dependent patients with DBA. Procedure Patients ≥2 years of age received L-leucine 700 mg/m2 orally three times daily for nine months to determine a hematologic response and any improvement in growth (NCT01362595). Results This multicenter, phase I/II study enrolled 55 subjects; 43 were evaluable. There were 21 males; the median age at enrollment was 10.4 years (range, 2.5-46.1 years). No significant adverse events were attributable to L-leucine. Two subjects had a complete erythroid response and five had a partial response. Nine of 25, and 11 of 25, subjects experienced a positive weight and height percentile change, respectively, at the end of therapy. Conclusions L-leucine is safe, resulted in an erythroid response in 16% of subjects with DBA, and led to an increase in weight and linear growth velocity in 36% and 44% of evaluable subjects, respectively. Further studies will be critical to understand the role of L-leucine in the management of patients with DBA.

Background and objective Recurrent hospital admissions for patients with sickle cell disease (SCD) are costly and contribute to a low quality of life for patients. We implemented a clinical pathway to safely discharge SCD patients with fever who are evaluated in the emergency department (ED) of a large tertiary care center. Methods An interdisciplinary team of ED and hematology physicians, nurses, and an improvement advisor developed a clinical pathway that identified febrile SCD patients at low risk of serious bacterial infection based on historical, clinical, and laboratory criteria who could be discharged from the ED. Phone follow-up was planned through the use of an automated electronic notification that was sent to an established hematology follow-up pool at the time of ED discharge. We conducted two "fake front end" trials in the ED to receive feedback on our process before full implementation. A postpathway implementation quality improvement team monitored discharge rates, phone follow-up rates and adverse events. Results In the first 9 weeks postpathway implementation, 100 SCD patients were evaluated for fever; 84 (24%) met low-risk criteria and were discharged home. This reduction in admission rate has been maintained throughout the 3 years postimplementation. Successful phone follow-up was achieved in all discharged patients within 24 hours and no adverse events were identified. Conclusions Low-risk febrile patients with SCD can be safely discharged from the ED. An automated notification system within the electronic medical record system can facilitate patient follow-up after ED discharge. Future quality improvement efforts aimed to further reduce admissions in this population should target patients with modifiable risk factors for serious bacterial infection.

Background: Hydroxyurea (HU) is the primary medication used to prevent the significant medical and neurologic morbidities of pediatric sickle cell disease (SCD; HbSS or HbSB0 thalassemia). Despite the benefits of HU, it remains under-utilized likely due to lack of clinician knowledge/training and negative caregiver perceptions. Thus, we developed the Engage-HU randomized controlled trial (NCT03442114) as a novel approach to address HU utilization barriers. Engage-HU is designed to assess how clinicians can engage caregivers in a shared discussion that considers their values, preferences, and scientific evidence about HU. The COVID-19 pandemic has resulted in significant changes to healthcare delivery for children with SCD, as they are at increased risk of severe illness from COVID-19 infection. Given their risk status, it was recommended that patients with SCD complete telehealth visits when possible. Some families also chose to delay care because they feared their child would get infected at hospitals/healthcare clinics that care for COVID-19 positive patients. Since the lives of all families enrolled in the Engage-HU trial have been affected to some extent, we incorporated measures to capture the impact of the COVID-19 pandemic and the usability of telemedicine implementation and services. Methods: Engage-HU is a randomized control trial comparing two dissemination methods for clinicians to facilitate shared decision-making with caregivers of young children with SCD. Study outcomes include caregiver confidence in decision-making and perceptions of experiencing shared decision-making as well as HU uptake and child health outcomes. Eligible children are 0 to 5 years, candidates for HU, and their caregiver has not decided about HU in the past 3 months. The trial is being conducted at 9 sites in the United States and uses a unidirectional crossover design. The primary endpoints are caregiver decisional uncertainty and caregiver perception of shared decision-making measured using validated tools. Data will be analyzed using the intent-to-treat principle, and all participants will remain in the arm to which they were randomized. A multiple group comparison analysis will be performed to assess significant response variable differences by group randomization. The Engage-HU study aims to recruit 174 caregivers who are considering initiating HU. The trial is being conducted at 9 sites in the United States. Data collection is ongoing, and 160 caregiver-participants have been enrolled to date. Since May 2020, caregiver-participants have completed the COVID-19 Exposure and Family Impact Scales (CEFIS), which contain 2 subscales (exposure to potentially traumatic aspects of the pandemic, impact on families), and the COVID-19 telemedicine use survey during a study visit. Results: Currently, 8 of the 9 sites have collected data from 48 caregivers (93.8% mothers), most of whom (93.8%) identify as African American/Black (see Figure 1). Correlations indicated that older caregivers experienced greater exposure (Mean = 7.0, SD = 4.1, range = 1-19) to potentially traumatic aspects of the pandemic (r = .31, p = .04). Distress related to COVID-19 varied widely across the sample, for both caregivers (Mean = 5.9, SD = 2.9, range = 1-10) and children (Mean = 4.1, SD = 3.4, range = 1-10). Scores on the telemedicine usability survey were generally high, indicating that caregivers are happy with the quality of care delivered via telehealth. However, caregivers (r = .30, p = .09) and children (r = .32, p = .07) experiencing more pandemic-related distress reported less satisfaction with telehealth. Conclusion: Although Engage-HU has resumed research operations, recruitment has not reached pre-pandemic targets, as fewer eligible patients are scheduled for routine care visits at SCD clinics. Our preliminary analyses suggest a significant continued impact of the pandemic on families and general satisfaction with the quality of healthcare delivered via telemedicine. These findings indicate that targeted screenings to identify and intervene for those who demonstrate more COVID-19 pandemic-related distress are needed. Figure 1 Figure 1. Disclosures Quinn: Forma Therapeutics: Consultancy; Aruvant: Research Funding; Novo Nordisk: Consultancy; Emmaus Medical: Research Funding. Yates: Agios Pharmaceuticals: Current Employment. Badawy: Sanofi Genzyme: Consultancy; Vertex Pharmaceuticals Inc: Consultancy; Bluebird Bio Inc: Consultancy. Thompson: bluebird bio, Inc.: Consultancy, Research Funding; Baxalta: Research Funding; Biomarin: Research Funding; Celgene/BMS: Consultancy, Research Funding; CRISPR Therapeutics: Research Funding; Vertex: Research Funding; Editas: Research Funding; Graphite Bio: Research Funding; Novartis: Research Funding; Agios: Consultancy; Beam: Consultancy; Global Blood Therapeutics: Current equity holder in publicly-traded company. Smith-Whitley: Global Blood Therapeutics: Current Employment. King: National Cancer Institute: Research Funding; National Heart, Lung, and Blood Institute: Research Funding; Health Resources and Services Administration: Research Funding; Global Blood Therapeutics: Research Funding. Meier: CVS Caremark: Consultancy; Forma Therapeutic: Membership on an entity's Board of Directors or advisory committees; NovoNordisk: Membership on an entity's Board of Directors or advisory committees; Novartis,: Other: Data Safety Monitoring Board membership; NHLBI: Other: Data Safety Monitoring Board membership; Global Blood Therapeutics: Other: Steering Committee membership, grant funding; CDC,: Other: grant funding; Indiana Department of Health: Other: grant funding . Tubman: Global Blood Therapeutics: Consultancy, Research Funding; Novartis Pharmaceuticals: Honoraria, Research Funding; Forma Pharmaceuticals: Consultancy; Perkin Elmer: Honoraria. Crosby: Forma Therapeutics: Honoraria; PCORI: Research Funding; HRSA: Research Funding; Global Blood Therapeutics Panel: Honoraria; Children's Hospital of Philadelphia: Honoraria; Professional Resource Exchange: Patents & Royalties: $30-$60 every other year; SCDAA: Honoraria; NHLBI: Other: Payment for review of LRP Proposals, Research Funding. OffLabel Disclosure: Hydroxyurea has been FDA approved for the treatment of sickle cell disease for patients ages 2 years and above but NHLBI and ASH Guidelines recommend it be offered to children as young as age 9 months.

Fanconi anemia (FA), a genetic disorder affecting DNA repair, is characterized by bone marrow failure and cancer susceptibility. In FA mouse models, metformin (N,N-dimethylguanide) a biguanide metabolic agent, improves blood counts and delays tumor development. Given these findings, we conducted a single institution pilot study of metformin in non-diabetic patients with FA to assess feasibility, tolerability, and impact of metformin on hematologic response as defined by modified MDS International Working Group (IWG) criteria (Table 1). Fourteen of 15 patients with at least 1 cytopenia (hemoglobin Figure 1 Figure 1. Disclosures Pollard: Kura Oncology: Membership on an entity's Board of Directors or advisory committees; Syndax: Membership on an entity's Board of Directors or advisory committees. Furutani: Keros Therapeutics: Current Employment, Current equity holder in publicly-traded company. Esrick: bluebird bio: Consultancy. Nakano: Novartis: Consultancy. Thompson: Celgene: Consultancy, Research Funding; bluebird bio: Consultancy, Research Funding; Biomarin: Research Funding; Vertex: Research Funding; Graphite Bio: Research Funding; Baxalta: Research Funding; CRISPR Therapeutics: Research Funding; Novartis: Research Funding; Agios Pharmaceuticals: Consultancy; Beam Therapeutics: Consultancy; Global Blood Therapeutics: Current equity holder in publicly-traded company. OffLabel Disclosure: metformin- use in Fanconi anemia in an effort to improve hematopoiesis

BACKGROUND Red blood cell (RBC) alloimmunization is a concern for patients who receive multiple or chronic transfusions. Alloimmunization prevalence in transfused patients with bone marrow failure syndrome (BMFS) is unknown. This study aimed to determine physician practice for RBC antigen matching, immunization rates, and antibody specificities in patients with BMFS. STUDY DESIGN AND METHODS The clinical records of all patients with BMFS seen at the Children's Hospital of Philadelphia between 2001 and 2015 were reviewed. Immunization rate was determined per 100 units transfused. RESULTS ABO/D, C, E, and K (CEK) RBC matching was requested for 21.8% of patients. A total of 3782 RBC units were transfused to 87 patients, of which 2551 (67.5%) were CEK matched and 1231 (32.5%) were ABO/D only matched. The majority of units transfused to patients on a chronic transfusion regimen were CEK matched (89.6% of 2728 units). No anti-C, -E, or -K antibodies formed in any patient during the 14-year study period. Two alloantibodies and two autoantibodies formed, resulting in a rate of 0.05 alloantibodies and 0.05 autoantibodies per 100 units transfused. The prevalence of alloimmunization was 2.3%. CONCLUSION The rate and prevalence of RBC alloimmunization were low in patients with BMFS. CEK matching avoided alloimmunization to these antigens in chronically transfused patients.

BACKGROUND R2* relaxometry's capacity to calculate liver iron concentration (LIC) is limited in patients with severe overload. Hemosiderin increases in these patients, which exhibits a non-monoexponential decay that renders a failed R2* analysis. PURPOSE/HYPOTHESIS To evaluate a biexponential R2* relaxometry model in children with different ranges of iron overload. STUDY TYPE Retrospective. POPULATION In all, 181 children with different conditions associated with iron overload. FIELD STRENGTH/SEQUENCE 1.5T, T2 *-weighted gradient echo sequence. ASSESSMENT Bi- and monoexponential R2* relaxometry were measured in the liver using two regions of interest (ROIs) using a nonproprietary software: one encompassing the whole liver parenchyma (ROI-1) and the other only the periphery (ROI-2). These were drawn by a single trained observer. The residuals for each fitting model were estimated. A ratio between the residuals of the mono- and biexponential models was calculated to identify the best fitting model. Patients with 1) residual ratio ≥1.5 and 2) R2*fast ≥R2*slow were considered as having a predominant biexponential behavior. STATISTICAL TESTS Nonparametric tests, Bland-Altman plots, linear correlation, intraclass correlation coefficient. Patients were divided according to their LIC into stable (n = 23), mild (n = 58), moderate (n = 61), and severe (n = 39). RESULTS The biexponential model was more suitable for patients with severe iron overload when compared with the other three LIC categories (P < 0.001) for both ROIs. For ROI-1, 37 subjects met criteria for a predominant biexponential behavior. The slow component (5.7%) had a lower fraction than the fast component (94.2%). For ROI-2, 22 subjects met criteria for a predominant biexponential behavior. The slow component (4.7%) had a lower fraction than the fast component (95.2%). The intraobserver variability between both ROIs was excellent. DATA CONCLUSION The biexponential R2* relaxometry model is more suitable in children with severe iron overload. LEVEL OF EVIDENCE 3 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2019;50:1191-1198.

Hepatitis‐associated aplastic anemia (HAA) is a variant of acquired aplastic anemia (AA) in which immune‐mediated bone marrow failure (BMF) develops following an acute episode of seronegative hepatitis. Dyskeratosis congenita (DC) is an inherited BMF syndrome characterized by the presence of short telomeres, mucocutaneous abnormalities, and cancer predisposition. While both conditions may cause BMF and hepatic impairment, therapeutic approaches are distinct, making it imperative to establish the correct diagnosis. In clinical practice, lymphocyte telomere lengths (TL) are used as a first‐line screen to rule out inherited telomeropathies before initiating treatment for AA. To evaluate the reliability of TL in the HAA population, we performed a retrospective analysis of TL in 10 consecutively enrolled HAA patients compared to 19 patients with idiopathic AA (IAA). HAA patients had significantly shorter telomeres than IAA patients (P = 0.009), including four patients with TL at or below the 1st percentile for age‐matched controls. HAA patients had no clinical features of DC and did not carry disease‐causing mutations in known genes associated with inherited telomere disorders. Instead, short TLs were significantly correlated with severe lymphopenia and skewed lymphocyte subsets, features characteristic of HAA. Our results indicate the importance of caution in the interpretation of TL measurements in HAA, because, in this patient population, short telomeres have limited specificity. Am. J. Hematol. 91:243–247, 2016. © 2015 The Authors. American Journal of Hematology Published by Wiley Periodicals, Inc.

Acquired aplastic anemia (aAA) is a nonmalignant disease caused by autoimmune destruction of early hematopoietic cells. Clonal hematopoiesis is a late complication, seen in 20–25% of older patients. We hypothesized that clonal hematopoiesis in aAA is a more general phenomenon, which can arise early in disease, even in younger patients. To evaluate clonal hematopoiesis in aAA, we used comparative whole exome sequencing of paired bone marrow and skin samples in 22 patients. We found somatic mutations in 16 patients (72.7%) with a median disease duration of 1 year; of these, 12 (66.7%) were patients with pediatric-onset aAA. Fifty-eight mutations in 51 unique genes were found primarily in pathways of immunity and transcriptional regulation. Most frequently mutated was PIGA , with seven mutations. Only two mutations were in genes recurrently mutated in myelodysplastic syndrome. Two patients had oligoclonal loss of the HLA alleles, linking immune escape to clone emergence. Two patients had activating mutations in key signaling pathways (STAT5B (p.N642H) and CAMK2G (p.T306M)). Our results suggest that clonal hematopoiesis in aAA is common, with two mechanisms emerging—immune escape and increased proliferation. Our findings expand conceptual understanding of this nonneoplastic blood disorder. Future prospective studies of clonal hematopoiesis in aAA will be critical for understanding outcomes and for designing personalized treatment strategies.

Diamond Blackfan anemia (DBA) is a rare, inherited bone marrow failure syndrome characterized by anemia, congenital anomalies and a predisposition to cancer. The patients usually present during infancy or early childhood, but can also present in adulthood. In the majority of cases DBA is due to a mutation in a small or large ribosomal protein (RP) subunit leading to RP haploinsufficiency. The only treatments for the anemia of DBA are red cell transfusions (accompanied by iron chelation), oral corticosteroid therapy or stem cell transplantation. Pospisilova et al. (Haematologica 2007; 92(5):e66-67) reported one complete and two partial erythroid responses after the use of the branched chain amino acid L-leucine in 6 select patients. In skeletal muscle, leucine supplementation can upregulate components of the protein synthetic machinery, including ribosomal proteins, promoting protein translation. Mouse and fish models of DBA respond with amelioration of anemia to L-leucine. We therefore proposed to study the effect of L-leucine on transfusion dependence and growth in subjects with DBA. Methods: The primary objectives were to determine the feasibility of administering L-leucine in subjects with DBA who are red cell transfusion-dependent and to determine the efficacy of L-leucine to produce a hematologic and growth response. The secondary objective was to determine the safety profile of L-leucine. Twelve study sites were involved in this multi-center, Phase I/II study with an anticipated accrual of 50 subjects. A dose of 700 mg/M2 orally three times per day for 9 months was used. Inclusion criteria included age > 2 years, the diagnosis of DBA and transfusion dependence with adequate kidney and liver function. Response was evaluated at 9 months with Complete Response (CR) defined as no further transfusions required and Hb >9; Partial Response (PR): Hb < 9 gm/dL with an increase in reticulocyte count and transfusion interval; and No Response (NR): no change in transfusion needs, Hb or reticulocyte count . Growth percentiles were evaluated at baseline and at completion of 9 months of treatment and the growth velocity change was calculated. Results: The study opened July 2014 and closed February 2017; 55 subjects were consented; 12 were screen failures; 43 subjects were evaluable. There were 21 males; the median age was 9 years 1 month (2 years 5 months - 46 years 1 month). There were no untoward side effects experienced by any subject that were attributable to the L-leucine. Two subjects had an erythroid CR and 1 subject had a PR. The CRs occurred at 1 month and 3 months after start of L-leucine. The subject with PR had an elevated reticulocyte count but was not able to maintain a Hb >9 gm/dL without a transfusion and thus was not transfusion independent. Of the 30 subjects with growth potential who received L-leucine 10 experienced a positive growth velocity change at 9 months of therapy compared to baseline. At a median age of 7.5 years, the mean pre-leucine height percentile was 27 +/- 17.9 and the post-leucine height percentile was 35 +/- 19.9 (p Conclusions: The administration of L-leucine is safe. L-leucine administration resulted in an erythroid response in 7% of subjects and an increased growth velocity in 33% of growing subjects. Based upon extrapolation from animal models, it is likely that this dose was suboptimal. We hypothesize that higher doses of L-leucine will lead to hematologic responses in more subjects who are transfusion dependent. The potential benefit of added growth in children with DBA may improve final adult height. Disclosures Glader: Agios: Consultancy, Research Funding.

Red blood cell (RBC) alloimmunization is a concern for patients who receive multiple or chronic transfusions. Alloimmunization prevalence in transfused patients with bone marrow failure syndrome (BMFS) is unknown. This study aimed to determine physician practice for RBC antigen matching, immunization rates, and antibody specificities in patients with BMFS.The clinical records of all patients with BMFS seen at the Children's Hospital of Philadelphia between 2001 and 2015 were reviewed. Immunization rate was determined per 100 units transfused.ABO/D, C, E, and K (CEK) RBC matching was requested for 21.8% of patients. A total of 3782 RBC units were transfused to 87 patients, of which 2551 (67.5%) were CEK matched and 1231 (32.5%) were ABO/D only matched. The majority of units transfused to patients on a chronic transfusion regimen were CEK matched (89.6% of 2728 units). No anti-C, -E, or -K antibodies formed in any patient during the 14-year study period. Two alloantibodies and two autoantibodies formed, resulting in a rate of 0.05 alloantibodies and 0.05 autoantibodies per 100 units transfused. The prevalence of alloimmunization was 2.3%.The rate and prevalence of RBC alloimmunization were low in patients with BMFS. CEK matching avoided alloimmunization to these antigens in chronically transfused patients.

[Figure][1] A 4-year-old girl with a known history of methylmalonic acidemia (MMA) complicated by acquired hypothyroidism, failure to thrive, and developmental delay developed pancytopenia during an admission for emesis and metabolic acidosis. She had no symptoms of a viral infection, and

[Figure][1] A 23-year-old man presented to our clinic for a second opinion. He was given the diagnosis of myelodysplastic syndrome (MDS) years prior, based on a history of iron overload and bone marrow biopsy findings of a hypercellular marrow with erythroid hyperplasia and

Acquired aplastic anemia (AA) is a hematologic disorder characterized by low blood counts and a hypocellular bone marrow, caused by autoimmune destruction of early hematopoietic cells. The diagnosis of AA is made by excluding other disorders that can present with bone marrow failure (BMF). Such disorders include dyskeratosis congenita (DC), a multisystem BMF syndrome, caused by an inherited defect in telomere maintenance. Although classical DC presents in childhood with stereotypical mucocutaneous changes, milder forms of telomere dysfunction associated with mutations in TERT and TERC genes can present with non-syndromic bone marrow failure clinically indistinguishable from AA. In clinical practice, lymphocyte telomere length measurements are used as a first-line screen for inherited telomeropathies before initiating treatment for AA. In our BMF center, we have observed that several patients with features of hepatitis-associated AA (HAA) had lymphocyte telomere lengths at diagnosis at or below the first percentile of age-matched controls, in the range similar to inherited telomere disorders. To confirm our initial observation, we performed a retrospective analysis of telomere lengths of consecutively enrolled HAA patients with non-hepatitis associated AA patients in our institution. A total of 30 patients with AA were included in this study: 10 had HAA and 20 had other AA (Table 1). The median age at telomere testing was 8.0 years (range 1-19 years). There was no significant difference in age or disease severity between the two groups (p=0.827). The patients' median lymphocyte telomere length (TL) was significantly lower in the HAA patients compared to AA (7.4kb versus 9.1kb, P= 0.021); the difference remained significant after adjusting for patient age (p Because differences in lymphocyte activation and subset composition are known to impact telomerase activity, we hypothesized that alterations in lymphocyte populations caused by the unique inflammatory state of HAA could partly account for significantly shorter TL in this population. HAA patients exhibited significantly lower absolute lymphocyte counts and lower lymphocyte subsets across the board, as well as the decreased CD4/CD8 ratio compared to non-hepatitis AA patients (Figure 2). The median telomere length in the two groups was significantly correlated with lymphocyte counts (Pearson correlation coefficient 0.52, p=0.003). An altered lymphocyte homeostasis such as the one characteristic for HAA limits the specificity of telomere measurements as a screening method to identify patients with AA due to a genetic defect in telomere maintaining genes. As such, short telomeres in HAA in the absence of other features suggestive for DC does not necessarily warrant genetic testing for telomere length. Longitudinal studies of telomeres and study of clonal hematopoiesis in this population is ongoing. Table 1. Overall (n = 30) AA (n=20) HAA (n=10) P value* Patient Characteristic Gender, female n (%) 12 (40) 9 (45) 3 (30) 0.694 Gender, male n (%) 18 (60) 11 (55) 7 (70) Age at diagnosis, y, median (range) 8.0 (1-19) 8.3 (1-19) 7.5 (3-17) 0.827 Disease Severity, n (%) 0.999 Moderate 6 (20) 4 (20) 2 (20) Severe 22 (73) 15 (75) 7 (70) Very Severe 2 (7) 1 (5) 1 (10) Median Lymphocyte Telomere Length, kb (range) 8.9 (5.9-11.3) 9.1 (7.5-11.3) 7.4 (5.9-9.8) 0.021 ≤ 1st percentile of age-matched controls 5 0 5 1-10th percentile of age-matched controls 5 5 0 > 10th percentile of age-matched controls 20 15 5 *P-values are obtained by Fisher's exact test for gender and disease severity and by Wilcoxon test for age and telomere length. Figure 1. Figure 1. Figure 2. Figure 2. Disclosures No relevant conflicts of interest to declare.

Clonal hematopoiesis is an expansion of hematopoietic stem cells, caused by somatic mutations or epigenetic changes that confer a growth advantage to the host cell. Although recently recognized as a phenomenon of aging, clonal hematopoiesis has been traditionally associated with pre-cancerous states and malignant transformation. Acquired aplastic anemia (AA), a non-neoplastic autoimmune blood disorder occurring in children and adults, has been associated with clonal hematopoietic disorders; transformation to myelodysplastic syndrome (MDS) or acute leukemia is a late complication in 10-15% of AA patients. Based on the association of AA with clonal disorders, we hypothesized that clonal hematopoiesis is a general phenomenon in AA, and can be seen in the majority of AA patients, including children. To evaluate somatic genetic changes in AA, we used a combination of single nucleotide polymorphism array (SNP-A) genotyping and comparative whole exome sequencing of paired bone marrow aspirates and skin in twenty nine patients with AA. All somatic mutations were validated by bi-directional Sanger sequencing. The median age of diagnosis was 14 years (range 1.5-65). Patients were analyzed at a median of 1.1 years from diagnosis. None of the patients had histopathological evidence of MDS at the time of analysis. Somatic mutations were identified in the majority of patients, including patients with pediatric-onset AA. Three patients (10%) had somatic loss-of-function mutations in HLA class I alleles. Although MDS-associated mutations were identified in 2 of 29 patients, the majority of mutations were not in genes associated with MDS and hematologic malignancies. Pathway analysis of mutated genes revealed an enrichment of genes in pathways of immunity and transcriptional regulation. Comparison of somatic mutations in AA to a patient with a 30-year history of AA who progressed to MDS revealed that, unlike in AA, which was characterized by diverse and frequently oligoclonal hematopoiesis, progression to MDS was associated with an expansion of a dominant clone carrying multiple classical mutations linked to malignancy: pathogenic mutations in SUZ12 (homozygous for the mutated region due to copy number-neutral loss of heterozygosity (CN-LOH) at the chromosomal region 17q11.2qter), ASXL1, RUNX1, and PHF6. In conclusion, our data show that clonal hematopoiesis emerges in the majority of patients with AA, including children and young adults, can be detected early in disease, and has a mutational spectrum largely distinct from MDS. Our results highlight that in the absence of morphologic features of myelodysplasia, the presence of clonal hematopoiesis with somatic mutations cannot be used to distinguish MDS from AA. Future longitudinal studies of clonal hematopoiesis in AA will help to explain differences in patients’ disease course, and will enable personalized treatment approaches in AA. Citation Format: Daria V. Babushok, Nieves Perdigones, Juan C. Perin, Timothy S. Olson, Wenda Ye, Jacquelyn J. Roth, Curt Lind, Carine Cattier, Yimei Li, Helge Hartung, Michele E. Paessler, Dale M. Frank, Hongbo M. Xie, Tracy M. Busse, Shanna Cross, Gregory M. Podsakoff, Dimitrios Monos, Jaclyn A. Biegel, Philip J. Mason, Monica Bessler. Most patients with acquired aplastic anemia develop clonal hematopoiesis early in disease. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2977. doi:10.1158/1538-7445.AM2015-2977