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There have been no large comparisons of the clinical and laboratory features of familial neonatal hemophagocytosis (f-nHLH) and infectious neonatal hemophagocytosis (i-nHLH). The objectives of this study were the following: (1) Describe the demographic, diagnostic, and clinical features of patients with familial nHLH (F-nHLH) and infectious HLH (i-nHLH). (2) Compare key variables between f-nHLH and i-nHLH. (3) Compare the clinical outcomes of f-nHLH and i-nHLH. (4) Summarize literature on cytokine levels in patients with nHLH. Data from a previously published nHLH meta-analysis report were used to describe and compare features of infants with f-nHLH versus i-nHLH. Variables were tested with the χ 2 test or Fisher exact test, Cochran-Armitage test, independent 2-sample t test, or Wilcoxon rank-sum test as appropriate. Odds ratios were calculated for any comparison with a P -value of <0.05. Data extracted from 99 cases of f-nHLH and 54 cases of i-nHLH were included in this analysis. Infants with f-HLH met HLH criteria at the following rates: fever (84%); organomegaly (100%); pancytopenia (75%); hypofibrinogenemia (84%); hypertriglyceridemia (48%); hypofibrinogenemia or hypertriglyceridemia (82%); hemophagocytosis (81%); hyperferritinemia (99%); low or absent NK cell activity (91%); and elevated soluble CCD25 (91%). Infants with i-nHLH had higher median ferritin levels (22,537 ng/mL) than infants with f-nHLH (7587 ng/mL) ( P =0.072). Infants with f-nHLH had higher rates of symptoms in utero, preterm birth, family history of HLH, and family history of infant death. The overall survival among infants with familial nHLH was lower than infectious nHLH ( P =0.037). Management of nHLH requires rapid diagnosis and prompt treatment, as current literature suggests nHLH has high mortality rates. Distinguishing between familial and infectious causes of nHLH can aid in determining the correct treatment of choice.

345 Background: Pediatric febrile neutropenia (PFN) requires emergent evaluation due to risk of invasive bacterial infection. In the management of PFN, there are varying, accepted definitions for fever requiring emergency evaluation and neutropenia requiring admission. Problem statement: From September 1, 2022 - May 31, 2023, 15.1% (n = 11/73) of emergency department (ED) visits and 17.1% (n = 6/35) of admissions for PFN at Mayo Clinic Rochester may be considered unnecessary due to patients not meeting updated clinical criteria. Aim: Decrease unnecessary ED visits and hospitalizations for PFN by 50% from 15.1% to 7.5% (for ED visits) and from 17.1% to 8.6% (for hospitalizations) by 02/29/2024 without adversely impacting mortality from invasive bacterial infection. Methods: We used the DMAIC framework for process improvement. Interventions included (1) adoption of a higher fever definition for PFN, (2) adoption of a risk-stratified neutropenia definition for hospital admission, (3) provided electronic fever plans with definitions to all families, (4) re-iterated that parents call on-call provider with any concern for fever, (5) educated pediatric oncology staff on definition and management of fevers in pediatric oncology patients, and (6) educated pediatric emergency department staff on definition and management of fevers in pediatric oncology patients. Interventions were tested with rapid tests of change. Relevant clinical characteristics, variables, and outcomes for all patients from pediatric oncology were tracked for all encounters of pediatric oncology patients presenting to the ED for acute illnesses. Results: At baseline,15.1% (n = 11/73) of ED visits for PFN were considered unnecessary due to patients not meeting clinical criteria for emergency evaluation. Post-interventions, unnecessary ED visits for PFN had decreased to 3.4% (n = 1/32). At baseline, 17.1% (n = 6/35) of hospitalizations were considered unnecessary due to patients not meeting clinical criteria for admission. Post-interventions, 7.7% (n = 2/26) of hospitalizations were considered unnecessary. There were no patient deaths from invasive bacterial infection among this cohort at baseline or after interventions. Conclusions: Multiple interventions including adoption of a higher, accepted fever threshold and risk stratified neutropenia definition for PFN was associated with a reduction of unnecessary ED visits and hospitalizations for PFN without an increase in mortality from invasive bacterial infection. The projected medical expense savings of approximately $144,000-$210,000 per year.

Post-transplant lymphoproliferative disorder is a rare and serious complication of organ and stem cell transplant secondary to immunosuppressive therapies, most commonly of monomorphic B-cell subtype. Here we describe the first reported case of a pediatric heart transplant patient who developed both monomorphic B-cell and nondestructive PTLD with plasmacytic hyperplasia followed by an unrelated case of monomorphic T-cell and nondestructive PTLD with plasmacytic hyperplasia, which later relapsed. We detail the patient’s risk factors for development of PTLD and her successful treatment regimens. This case highlights the potential relationship between Epstein-Barr virus and/or cytomegalovirus and PTLD.

Background/Objectives: The enzyme ubiquitin-specific protease 44 (USP44) is a deubiquitinating enzyme with identified physiological roles as a tumor suppressor and an oncogene. While some binding partners and substrates are known for USP44, the identification of other interactions may improve our understanding of its role in cancer. We therefore performed a proximity biotinylation study that identified products of several known cancer genes that are associated with USP44, including a novel interaction between BRCA2 and USP44. Methods: We expressed a fusion protein that linked USP44 and mutant Escherichia coli biotin ligase BioID in SH-SY5Y neuroblastoma cells. Control experiments were performed using BioID alone. In duplicate experiments, cells were pulsed with biotin and biotinylated proteins were isolated under denaturing conditions and the proteins were identified by mass spectrometry. The resulting list of proteins were analyzed using Enrichr and cross-referenced with the COSMIC Cancer Gene Census. We validated the association with BRCA2 using immunoprecipitation. The role of USP44 in the Fanconi anemia DNA repair pathway was investigated using chromosome analysis of wild-type or Usp44-knockout cells after exposure to mitomycin C. Results: We identified 146 proteins that were selectively retrieved by the USP44 construct and compared with cells expressing the BioID ligase alone, including 15 gene products encoded by genes on tier 1 of the COSMIC Cancer Gene Census, including BRCA2. The association between USP44 and BRCA2 was validated through immunoprecipitation. We tested the functional role of USP44 in the Fanconi anemia DNA repair pathway through chromosome breakage analysis and found that cells lacking USP44 had a significant increase in chromosome breaks and radial chromosomes. We found that high BRCA2 transcript was correlated with poor survival in neuroblastoma, likely due to its tight association with proliferation in these tumors. Conclusions: Our results identified novel potential binding partners and potential substrates for USP44, including several with direct roles in cancer pathogenesis. Our results identified a novel association between BRCA2 and USP44, and a previously unknown role for USP44 in the Fanconi anemia DNA repair pathway that may contribute to its role in cancer.

ABSTRACTAthletes are at high risk of iron deficiency even without anemia. In this systematic review and meta‐analysis that included 17,519 athletes in 122 references from 23 countries, participating in 62 unique sports over a 41‐year timeframe, approximately 53.9% of student‐athletes were found to be hypoferritinemic (ferritin concentration below 50 mcg/L) with 23.0% percent showing absolute iron deficiency based on current definitions (ferritin concentration below 20 mcg/L). These findings strongly suggest that changes in clinical practice guidelines are warranted to enable routine screening for iron deficiency among adolescent and collegiate athletes.

ABSTRACTObjectiveIron and other biologically important metals are essential to mitochondrial function but are not routinely evaluated. Their equilibrium is critical to the optimal performance of cells with high metabolic activity such as neurons, cardiomyocytes, and skeletal myocytes. Teenagers are at a high risk of iron deficiency even without anemia. Metal ion imbalances can cause cognitive impairments, muscle weakness, and sudden cardiac death. We aim to assess the current prevalence of iron deficiency among collegiate athletes in the Upper Midwest.MethodsOur study is a multicenter, retrospective chart review of outpatient clinics in a regional healthcare system between January 2012 and December 2023, and a national public database between 2017 and March 2020. We reviewed the ferritin concentrations of regional collegiate athletes having preparticipation sport evaluations and nationally in the NHANES database.ResultsWe identified 643 unique individuals aged 16–21 years with 253 having ferritin screening. Iron deficiency (ferritin <20 mcg/L) was present in 24.5% and hypoferritinemia (ferritin <50 mcg/L) was present in 66.7% of collegiate athletes. From the NHANES database, 12.7% of active sampled participants aged 16–21 years were iron deficient.ConclusionOur study findings suggest the need for universal screening for iron deficiency among collegiate athletes given the high prevalence of iron deficiency in both the retrospective chart review and NHANES database analysis. Given the critical role of metal ion homeostasis to optimal mitochondrial function, these findings may warrant the inclusion of ferritin testing in cardiac, neurological, and skeletal muscle evaluations.

Abstract Neuroblastoma is an embryonic cancer that contributes disproportionately to death in young children. Sequencing data have uncovered few recurrently mutated genes in this cancer, although epigenetic pathways have been implicated in disease pathogenesis. We used an expression-based computational screen that examined the impact of deubiquitinating enzymes on patient survival to identify potential new targets. We identified the histone H2B deubiquitinating enzyme USP44 as the enzyme with the greatest impact on survival in patients with neuroblastoma. High levels of USP44 significantly correlate with metastatic disease, unfavorable histology, advanced patient age, and MYCN amplification. The subset of patients with tumors expressing high levels of USP44 had significantly worse survival, including those with tumors lacking MYCN amplification. We showed experimentally that USP44 regulates neuroblastoma cell proliferation, migration, invasion, and neuronal development. Depletion of the histone H2B ubiquitin ligase subunit RNF20 resulted in similar findings, strongly implicating this histone mark as the target of USP44 activity in this disease. Integration of transcriptome and epigenome in analyses demonstrates a distinct set of genes that are regulated by USP44, including those in Hallmark MYC target genes in both murine embryonic fibroblasts and the SH-SY5Y neuroblastoma cell line. We conclude that USP44 is a novel epigenetic regulator that promotes aggressive features and may be a novel target in neuroblastoma. Implications: This study identifies a new genetic marker of aggressive neuroblastoma and identifies the mechanisms by which its overactivity contributes to the pathophysiology of this disease.