Severe aplastic anemia (SAA) is treated with a hematopoietic cell transplant (HCT) in the presence of an HLA-matched sibling donor (MSD) with disease-free survival (DFS) of >90%. In the absence of an MSD, immunosuppressive therapy (IST) can induce remission but concerns for relapsed/refractory disease and clonal hematopoiesis persist. IST failure is an indication for HCT. Modern HCT approaches target barriers such as graft rejection (GR), graft-versus-host disease (GVHD), and transplant-related toxicities. Traditionally, total body irradiation (TBI) inclusive HCT conditioning helps decrease GR, but the use of TBI in children increases concerns for late effects such as malignancies. To describe outcomes after HCT in children with SAA transplanted from the best available donor following a radiation-free RIC regimen in a single-center feasibility trial. The RIC regimen included alemtuzumab, fludarabine, melphalan, ±thiotepa prior to HCT GVHD prophylaxis included tacrolimus, methotrexate, or mycophenolate mofetil. Abatacept was added to GVHD prophylaxis after 2017 to decrease further or eliminate GVHD risk in patients with a non-malignant disorder. This report includes outcomes in 22 consecutive pediatric SAA recipients of HCT (11 MSD, 10 unrelated, and 1 haploidentical) between 2012 and 2023 at a single center. With a median follow-up of 48 months (range, 12-144) all recipients had sustained full myeloid donor chimerism, 100% DFS, and no grade 2 to 4 acute GVHD. One patient (4.5%) developed grade 1 acute skin GVHD, and 1 (4.5%) developed pericardial effusion attributed to chronic GVHD. Complications before day +180 were primarily transient viral reactivations. Thyroid and ovarian hypofunction were the commonest effects noted at long-term follow-up. This radiation-free RIC regimen demonstrated excellent DFS with minimal GVHD in all patients, including those from alternative donor sources. Late complications were primarily endocrine in origin.

Background:Childhood idiopathic severe aplastic anemia (SAA) treated with hematopoietic cell transplantation (HCT) from an HLA-matched sibling donor (MSD) has an overall survival (OS) of >90%. Immunosuppressive therapy (IST) is recommended in patients who lack MSD. Recently, unrelated donor (URD) and haploidentical (HI) transplants have gained favor due to better outcomes with reduced intensity regimens that include low dose total body irradiation (TBI) to avert graft rejection with cyclophosphamide and/or fludarabine. However, avoiding TBI to prevent potential long-term toxicities from the same, could benefit recipients, especially young children. We tested a radiation-free, reduced intensity conditioning (RIC) regimen in pediatric SAA and report outcomes. Methods: We retrospectively analyzed 23 patients, consecutively transplanted at St. Louis Children's Hospital between 2013 and 2023. The median age at diagnosis was 10 years (range, 3-19). Fourteen (61%), failed IST prior to transplant. All patients received alemtuzumab (48 mg, day -21 to 18), fludarabine (150 mg/m2; day -8 to -4) and melphalan (140 mg/m2; day -3). Thiotepa (8 mg/kg; day -4) was included for mismatched or cord blood transplants (CBT). GVHD prophylaxis included tacrolimus (tapered after 6-9 months), abatacept (10 mg/kg/dose; 5 doses until day 100 if CBT, 8 doses until day 365 if marrow donor), methotrexate (7.5 mg/m2 on days 1, 3 and 6 if marrow donor) and mycophenolate mofetil (until day 28 if CBT). Results: Twelve patients (52%) received MSD, 9 (39%) URD and 2 (8%) HI transplants. Thirteen (56%) were HLA-matched (8/8), others were one-antigen mismatched (7/8). Bone marrow was the primary graft source in 18 (78%), peripheral blood in 3 (13%) and cord in 2 (8%) patients. The median age at HCT was 11 years (range, 3-20). The median time from diagnosis to HCT was earlier in MSD than URD and HI groups (3.5 months versus 9 months respectively). Twenty-two patients survived beyond day +30 and achieved 100% donor chimerism. One died on day +1 due to pneumocystis and staphylococcal infections diagnosed pre-transplant. Neutrophil and platelet engraftment were comparable in MSD and URD/HI groups (median at 15 and 30 days respectively). At 1 year post HCT, all survivors exhibited full donor myeloid and lymphoid chimerism of > 95%. The absolute lymphocyte numbers for CD4 T cells (median 548 cells/µL, range, 283-1056), CD8 (median 354 cells/µL, range, 282-1996) and B cells (median 379 cells/µL, range, 270-900) reached normal range at 1 year post-HCT. One patient developed steroid responsive grade I acute skin GVHD. No patient had graft failure or chronic GVHD. OS and event-free survival were 95% at a median follow-up of 48 months (range, 12-144). No patient developed malignancy or clonal hematopoiesis during the follow-up period. Toxicities included bacterial infections in 2 (8%) and asymptomatic viral reactivation in 10 patients (43%) within 100 days post-transplant. Late complications (>day 100) included 1 patient with rituximab-responsive autoimmune hemolytic anemia, 5 (22%) with delayed puberty/secondary amenorrhea, 2 (8%) with thyroid dysfunction, 1 with growth hormone deficiency, and 4 (17%) with depression, memory or attention abnormalities that impacted school performance. Conclusion:Overall,this radiation-free RIC regimen affordedexcellent disease-free survival rates in children with SAA irrespective of donor source, HLA-match, and recipient age. This approach provides an alternative conditioning regimen in patients that can benefit from avoiding radiation exposure. Late complications primarily affected endocrine and gonadal function, likely influenced by both pre-transplant factors such as iron overload and transplant conditioning.

BACKGROUND:Tissue factor pathway inhibitor (TFPI) regulates tissue factor-triggered coagulation. Humans and mice express transcripts encoding for multidistributed (endothelial, platelet, and plasma) 3-Kunitz domain TFPIα and endothelial membrane-anchored 2-Kunitz TFPIβ. Mice express a third transcript, γ, that encodes plasma lipoprotein-associated 2-Kunitz TFPI. In humans, proteolysis of α and/or β produces plasma lipoprotein-associated 2-Kunitz TFPI at lower levels. In clinical trials, monoclonal antibodies that target all TFPI isoforms extend coagulation and correct bleeding in hemophilic patients but with some thrombosis risks. OBJECTIVES:To determine the impact of TFPI isoform-specific deletions on promoting clotting in hemophilic mice. METHODS:Engineered TFPI isoform-specific, hemophilic (factor VIII-null) mice were evaluated for clotting. RESULTS:Mice expressing any single TFPI isoform were healthy. Thrombin generation assays identified TFPIγ as the dominant anticoagulation isoform in mouse plasma. Hemostasis was assessed by serial bleeding times from a tail vein laceration. Repeatedly, after a clot forms, it was manually disrupted; the number of clots/disruptions occurring over a 15-minute period were reported. C57BL/6 and hemophilic mice clot on average 25.6 vs 5.4 times, respectively. On a hemophilia background, TFPIβ or TFPIγ-specific deletion improved clotting to 14.6 and 15.2 times, respectively (P < .0001). TFPIα-specific deletion was without impact, clotting 5.1 times. Heterozygous deletion of TFPIβ was effective, clotting 11.8 times (P < .0001). Heterozygous deletion of TFPIα or TFPIγ alone was ineffective, clotting 3.0 and 6.1 times, respectively, but heterozygous TFPIαγ deletion improved clotting to 11.2 times (P < .001). CONCLUSION:In hemophilic mice, endothelial TFPIβ and plasma γ-derived 2-Kunitz TFPI individually contribute more to bleeding than total TFPIα.

Background:Red cell distribution width (RDW) has been used in the differential diagnosis of anemia and revealed to be a potential marker of inflammation. Method:We conducted a retrospective study of acute-phase reactant changes in correlation with RDW among pediatric patients with osteomyelitis. Results:We identified 82 patients whose mean RDW increased on average by 1% during antibiotic therapy (mean 13.9% on admission, 95% CI 13.4-14.3, and 14.9% at the end of antibiotic therapy, 95% CI 14.5-15.4). Overall, the RDW was weakly correlated with absolute neutrophil count (r = -0.21, P = 0.001), erythrocyte sedimentation rate (r = -0.17, P = 0.007), and C-reactive protein (r = -0.21, P = 0.001). The generalized estimating equation model showed a weak negative correlation between RDW and C-reactive protein during the therapy duration (B= -0.03, P = 0.008). Conclusions:The mild increase in RDW, and its weak negative correlation with other acute-phase reactants during the study course, limits its utility as a therapy response marker in pediatric osteomyelitis.

Key Points: Expression of any single TFPI isoform (α, β, or γ) is sufficient for mouse survival.Two-Kunitz domain TFPI isoforms, anchored β and circulating γ, each contribute to hemophilia bleeding.In vivo, TFPIβ is a more potent anticoagulant than TFPIα. Upon injury, tissue factor (TF) triggers coagulation by complexing with factor (F)VIIa to activate FIX and FX, leading to thrombin generation and a fibrin clot. Tissue factor pathway inhibitor limits TF-triggered coagulation. Humans and mice express transcripts encoding for 3-Kunitz domain TFPIα and membrane-anchored 2-Kunitz TFPIβ. Mice also express transcripts encoding untethered, 2-Kunitz TFPIγ. In humans, proteolysis of TFPIα and/or β produces “γ-like” 2-Kunitz TFPI. Hemophilia A and B, caused by deficiency in factors VIII and IX, respectively, are congenital X-linked recessive bleeding disorders that affect an estimated 1.1 million males worldwide. Hemophilia can cause excessive bleeding spontaneously or in response to trauma that can be life-threatening or significantly decrease the quality of life. Approved treatments for hemophilia include factor replacement, bypassing agents, the bispecific antibody Emicizumab, and recently approved gene therapies. Also in development are agents that reduce endogenous anticoagulant activity to counter the procoagulant deficiency of hemophiliacs, including monoclonal antibodies (Mab) to TFPI. These Mab target all TFPI isoforms to improve coagulation and correct bleeding in hemophilia patients, but with some demonstrated thrombosis risk. We investigated if TFPI-isoform-specific inhibition could provide equivalent efficacy which might reduce thrombotic risk. We generated TFPI-isoform-specific exon deletions in mice bred into hemophilia (FVIII-null) background. We find mice expressing any single TFPI isoform (α, β, or γ) appear healthy and reproduce. Our in vivo tail-vein re-bleeding assay is based on serial clot disruptions over 15 minutes, which we have shown is sensitive to anticoagulant and antiplatelet treatment, as well as factor replacement therapy. In this assay, we find C57Bl/6 WT mice clot 25.6 + 0.8 times (mean + SEM), whereas FVIII-null hemophilia mice clot 5.3 +0.4 times. In hemophilia mice, TFPIα-specific deletion is without impact, forming clots 5.1 + 0.8 times, whereas TFPIβ-specific or TFPIγ-specific deletion improves clot formation to 16.8 + 2.0 and 15.2 + 1.5 times, respectively (p<0001). Even hemophilia mice with heterozygotic deletion of the β exon form clots 11.8 + 0.8 times (p<0001). Thus, in vivo 2-Kunitz TFPI isoforms, anchored β and untethered γ each provides greater anticoagulant activity and impact on bleeding than 3-Kunitz TFPIα. Ex vivo plasma-based thrombin generation assays show that TFPIγ provides more anticoagulant activity than TFPIα. As shown in the figure, the deletion of TFPIγ increases thrombin generation to a greater extent than the deletion of TFPIα. The addition of an anti-TFPI antibody that effectively blocks TFPI activity shows a significant increase in endogenous thrombin potential in the plasma of TFPIαβ-deleted (γ-only) mice (370 nM.min), versus TFPIβγ-deleted (α-only) plasma (70 nM.min) and TFPIαγ-deleted (β-only) mice plasma (22 nM.min), (p<0.001). As expected, membrane-anchored TFPIβ is not detected in plasma. It is well established that 3-Kunitz TFPIα is a potent anticoagulant in plasma-based clotting time assays, while truncated 2-Kunitz TFPI, like mouse TFPIγ, appears inactive. Based on such assays, it was unexpected that TFPIγ-only expressing mice thrive, and in vivo, TFPIα is not the dominant endogenous anticoagulant. If mouse models are to be useful in providing insights into human hemostasis and TF-associated diseases, then it is critical to understand the similarities and differences between mice and humans. As humans do not express TFPIγ, the observed impact of depleting circulating 2-Kunitz TFPI on bleeding and thrombin generation in hemophilic mice is unlikely to translate to man. By contrast, our results demonstrating that, in vivo, TFPIβ is a more potent anticoagulant than TFPIα in mice has potential therapeutic implications in humans.

Hyperammonemia has been reported following asparaginase administration, consistent with the mechanisms of asparaginase, which catabolizes asparagine to aspartic acid and ammonia, and secondarily converts glutamine to glutamate and ammonia. However, there are only a few reports on the treatment of these patients, which varies widely from watchful waiting to treatment with lactulose, protein restriction, sodium benzoate, and phenylbutyrate to dialysis. While many patients with reported asparaginase-induced hyperammonemia (AIH) are asymptomatic, some have severe complications and even fatal outcomes despite medical intervention. Here, we present a cohort of five pediatric patients with symptomatic AIH, which occurred after switching patients from polyethylene glycolated (PEG)- asparaginase to recombinant Crisantaspase Pseudomonas fluorescens (4 patients) or Erwinia (1 patient) asparaginase, and discuss their subsequent management, metabolic workup, and genetic testing. We developed an institutional management plan, which gradually evolved based on our local experience and previous treatment modalities. Because of the significant reduction in glutamine levels after asparaginase administration, sodium benzoate should be used as a first-line ammonia scavenger for symptomatic AIH instead of sodium phenylacetate or phenylbutyrate. This approach facilitated continuation of asparaginase doses, which is known to improve cancer outcomes. We also discuss the potential contribution of genetic modifiers to AIH. Our data highlights the need for increased awareness of symptomatic AIH, especially when an asparaginase with higher glutaminase activity is used, and its prompt management. The utility and efficacy of this management approach should be systematically investigated in a larger cohort of patients.

To the Editor: Histiocytosis is a macrophageand dendritic cell-derived infiltrative disorder driven by somatic variants in the MAPK cell-signaling pathway.1 World Health Organization recently classified ALK-positive histiocytosis as a new entity mainly driven by ALK (anaplastic lymphoma kinase) rearrangements, especially KIF5B–ALK fusions, leading to constitutive activation of ALK tyrosine kinase.2 Herein, we describe the youngest reported pediatric patient to be successfully treated for the central nervous system (CNS)-involved ALK-positive histiocytosis with lorlatinib, an ALK-inhibitor with CNS penetration. The patient was a 7-month-old female who presented with regression of developmental milestones, failure to thrive, and frequent vomiting. Her physical exam was remarkable for macrocephaly, bilateral upward gazepalsy, andhypotonicity. Theheadmagnetic resonance imaging (MRI) showeda4.7×3.2 cmT2hyperintensemass arising from thalamic hemispheres. The lesion was extending into the third ventricle, obstructing the cerebral aqueduct with marked dilatation of the lateral and third ventricles (Figure 1A,B). She underwent endoscopic ventriculostomy and temporary external ventricular drainage. Tumor biopsy demonstrated a monomorphic infiltrate of pink cells with variable spindled to ovoid focally indented nuclei. There were intermixed eosinophils and lymphocytes without evidence of xanthomatous or Toutongiant cells. TheCD163showed that the lesionmainly consists of histiocytes with factor XIIIa diffusely positive. CD1a and BRAF V600E were negative. The ALK1 immunostaining showed granular cytoplasmic staining and ALK rearrangement at 67.5% of the 200 cells per FISH technique (Figure 1D–G). Targeted RNA sequencing confirmed KIF5B–ALK fusion.Whole-body fluorodeoxyglucose-positron emission tomography computed tomography (FDG-PET-CT) confirmed only CNS involvement (Figure 1C). Given the high-risk nature of the debulking surgery and the side effect profile of radiotherapy and conventional chemotherapy in an infant, we pursued ALK inhibition with lorlatinib. The patient started lorlatinib at 95 mg/m2/dose oral solution daily by crushing tablets into a flavored suspending vehicle (ORA-Plus). After 2 months of therapy, she started to gain weight and her motor tone and strength improved (Figure 2A). Short-interval MRI after 2 months of treatment demonstrated partial response per RANO (Response Assessment in Neuro-Oncology) criteria3 of her thalamic lesion, nowmeasuring 2.2× 1.4 cmwith complete resolution of the left thalamic component and interval improvement in obstructive hydrocephalus (Figure 2B,C). After 6months of therapy, she started crawling and eating solid foods and had stable right-sided weakness on exam. Following 12 months of treatment, the patient regained head control, motor tone and strength, expressive language, and tolerating solid foods, andMRI showed resolutionof contrast enhancementwith stable mass size (Figure 2D). After 18 months of therapy, the patient walked without support, and imaging remained stable (Figure2E). Shehasbeen immunized appropriately for her age and has not developed any severe infections. Grade 2 hyperlipidemia and grade 3 high cholesterol developed on lorlatinib treatment, and the patient required statins at the end of 18 months. She also developed a grade 1 increase in alanine aminotransferase that can be related to her high cholesterol level. When she could not receive lorlatinib for a month, the lipid panel was normalized, which was also consistent with a side effect. Her blood pressure, electrocardiograms, and echocardiograms have been closely monitored and remained reassuring. She continues therapies with an early childhood intervention program. To date, she has tolerated lorlatinib for 18 months and continues showing radiological response and developmental improvements. Kemps et al. classified ALK-positive histiocytosis in the largest patient cohort into the liver and hematopoietic systems involved (Group 1A), multisystemic (Group 1B), and single-system diseases (Group 2). About half of the multisystemic and single-system disease groups are associated with CNS involvement.4 Around 20 CNSinvolved ALK-positive histiocytosis cases have been reported with treatments including surgical resection and conventional chemotherapy (vinblastine, steroids, vincristine, cytarabine, methotrexate); the ALK inhibitors alectinib, crizotinib, and brigatinibwere used as secondline therapies alone or in combination with conventional chemotherapy with an objective response in most cases (10 of 11 patients), except one failure of disease control with crizotinib-based systemic treatment.4–6 The optimal duration of treatmentwith ALK inhibitors is unclear. CNS involvement provides an added challenge as the tumor may not be amenable to total resection, which mandates using other therapeutic approaches. At the time of our case, the only FDA-approved pediatric ALK inhibitorwas crizotinib, which has poorCNSpenetrance. Bresler et al. described ALK genomic status as an essential subclassification tool in neuroblastoma, allowing ALK-targeted therapy.7 Good CNS penetrance of lorlatinib and activity against crizotinib-resistant ALK mutations permitted use in the first pediatric phase I clinical trial for neuroblastoma.8 Based on this prior phase I pediatric trial, we targeted dosing between 0.7 and 0.95mg/m2.

Tissue factor (TF) is a transmembrane receptor that initiates coagulation and, via protease-activated receptors, enhances inflammation. Tissue factor pathway inhibitor (TFPI) is the endogenous regulator of TF activities. Anti-TFPI antibodies show promise as a hemophilia treatment but must be tittered to avoid potential thrombogenic side effects. From a single gene, through alternative splicing, humans express TFPI transcripts that encode for α and β isoforms; while mice express transcripts that encode for α and β, and also a third isoform γ, which is the most abundant. It is hypothesized that TFPIα is the dominant isoform anti-coagulant in man, whereas cell-anchored TFPIβ is the dominant anti-inflammatory. The main goal of our study is to further understand the impact of the different TFPI isoforms in hemophilic mice. To assess the functions of the α, β, and γ mouse-specific TFPI isoforms, using CRISPR/Cas9 technology, we generated TFPI α-, β-, γ-, α/β-, α/γ-, and β/γ- deleted mouse strains. Each knock-out strain is viable, and the offspring were born with expected Mendelian ratios. To evaluate the hemostatic function of the individual isoforms, all TFPI mice strains were bred on a hemophilia (FVIII-null) background and evaluated with a tail-vein rebleeding assay (TVRB). In this TVRB, a lateral tail vein is transected to cause bleeding; time to clot formation is recorded, then the clot is immediately dislodged, and the process is repeated over 15 minutes. In this assay, C57/Bl6 mice clot on average 26 +1.3 (mean+SD) times, whereas F8 null mice clot 5 + 2.6 times on average. Surprisingly, in the F8 null background, deletion of TFPIγ (14 + 6.5), alone or in combination as α/γ-deleted or β/γ-deleted, significantly reduced bleeding (p < 0.001), whereas TFPIα deletion had no impact on hemophilia bleeding (5 + 3). We next performed ex-vivo thrombin generation assays (TGA). The blood was collected via the inferior vena cava into corn trypsin inhibitor plus citrate syringes. Platelet-poor plasma was extracted and added into 96-well plates in addition to TF, phospholipids, calcium, and substrate. Endogenous thrombin potential was calculated from the area under the curve for generated thrombin for each TFPI mice strain on a hemophilia background. In agreement with the in vivo model, TFPIγ-deletion on the F8 null background significantly improved endogenous thrombin potential (P=0.037), while additional deletion of TFPIα (α/γ-deletion) did not provide any additional procoagulant effect. In conclusion, both in vivo and ex vivo hemostasis mouse models showed that, rather than three Kunitz TFPIα or cell-anchored TFPIβ, soluble two-Kunitz domain TFPIγ is the dominant mouse plasma isoform with respect to anti-coagulant function. Studies using mouse models that investigate the role of TFPI in hemostasis, thrombosis, and inflammation must carefully consider and address the impact of mouse TFPIγ on outcomes before extrapolating findings to human TFPI in health and disease.

BACKGROUND:Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is associated with excessive coagulation, thrombosis, and mortality. OBJECTIVE:To provide insight into mechanisms that contribute to excessive coagulation in coronavirus 2019 (COVID-19) disease. PATIENTS/METHODS:Blood from COVID-19 patients was investigated for coagulation-related gene expression and functional activities. RESULTS:Single-cell RNA sequencing (scRNA-seq) of peripheral blood mononuclear cells from severe COVID-19 patients revealed a 5.2-fold increase in tissue factor (TF [F3 gene]) transcript expression levels (P < .05), the trigger of extrinsic coagulation; a 7.7-fold increase in C1-inhibitor (SERPING1 gene; P < .01) transcript expression levels, an inhibitor of intrinsic coagulation; and a 4.4-fold increase in anticoagulant thrombomodulin (TM [THBD gene]) transcript expression levels (P < .001). Bulk RNA-seq analysis of sorted CD14+ monocytes on an independent cohort of COVID-19 patients confirmed these findings (P < .05). Indicative of excessive coagulation, 41% of COVID-19 patients' plasma samples contained high D-dimer levels (P < .0001); of these, 19% demonstrated extracellular vesicle TF activity (P = .109). COVID-19 patients' ex vivo plasma-based thrombin generation correlated positively with D-dimer levels (P < .01). Plasma procoagulant extracellular vesicles were elevated ∼9-fold in COVID-19 patients (P < .01). Public scRNA-seq data sets from bronchoalveolar lung fluid and our peripheral blood mononuclear cell scRNA-seq data show CD14+ monocytes/macrophages TF transcript expression levels are elevated in severe but not mild or moderate COVID-19 patients. CONCLUSIONS:Beyond local lung injury, SARS-CoV-2 infection increases systemic TF (F3) transcript levels and elevates circulating extracellular vesicles that likely contribute to disease-associated coagulation, thrombosis, and related mortality.

ALK-positive histiocytosis is a rare subtype of histiocytic neoplasm first described in 2008 in 3 infants with multisystemic disease involving the liver and hematopoietic system. This entity has subsequently been documented in case reports and series to occupy a wider clinicopathologic spectrum with recurrent KIF5B-ALK fusions. The full clinicopathologic and molecular spectra of ALK-positive histiocytosis remain, however, poorly characterized. Here, we describe the largest study of ALK-positive histiocytosis to date, with detailed clinicopathologic data of 39 cases, including 37 cases with confirmed ALK rearrangements. The clinical spectrum comprised distinct clinical phenotypic groups: infants with multisystemic disease with liver and hematopoietic involvement, as originally described (Group 1A: 6/39), other patients with multisystemic disease (Group 1B: 10/39), and patients with single-system disease (Group 2: 23/39). Nineteen patients of the entire cohort (49%) had neurologic involvement (7 and 12 from Groups 1B and 2, respectively). Histology included classic xanthogranuloma features in almost one-third of cases, whereas the majority displayed a more densely cellular, monomorphic appearance without lipidized histiocytes but sometimes more spindled or epithelioid morphology. Neoplastic histiocytes were positive for macrophage markers and often conferred strong expression of phosphorylated extracellular signal-regulated kinase, confirming MAPK pathway activation. KIF5B-ALK fusions were detected in 27 patients, whereas CLTC-ALK, TPM3-ALK, TFG-ALK, EML4-ALK, and DCTN1-ALK fusions were identified in single cases. Robust and durable responses were observed in 11/11 patients treated with ALK inhibition, 10 with neurologic involvement. This study presents the existing clinicopathologic and molecular landscape of ALK-positive histiocytosis and provides guidance for the clinical management of this emerging histiocytic entity.

Baseline population opinions on human papillomavirus (HPV) and HPV vaccination must be understood before physicians can address knowledge gaps in that population and encourage timely vaccination. To determine the opinions of parents of children age 9 to 18 on HPV-related oropharyngeal cancers (OPC); the associations with education level, socioeconomic status, and having a family member/friend with OPC; and the main concerns against having a vaccination., An anonymous survey was created and administered. Parents were asked to complete the survey if they met the inclusion criteria. After the survey, results were tabulated, and the answers for each question were analyzed. The target population was surveyed in the clinic. The target population was parents with children between 9 and 18 years old: the background knowledge and awareness of HPV-related OPC and associations with education level, socioeconomic status, having a family member/friend with OPC, and concerns about vaccination. Our study results showed that the age of parents, education level, marital status, personal vaccination status, and gender of the child are significant factors for background knowledge about HPV-related diseases. Similarly, the education level, the gender of the child, and personal vaccination status are significant factors towards attitudes against having children vaccinated. There is a strong correlation between background knowledge and attitudes. The main issues about vaccination are concerns about effectiveness and side effects, concerns about safe sex experiences, and the cost of vaccination. This is the first study designed to provide information on parents’ knowledge of HPV-related cancers, prevalence of HPV vaccination, and attitudes and concerns about HPV vaccination in the USA. The lack of awareness of HPV-related cancers is a significant factor in attitudes against HPV vaccination.

One in 40 pediatric office visits in the United States result in referral to subspecialty care, mostly for secondary opinion. The aim of this study was to evaluate the necessity of pediatric hematology referrals from Eastern New Mexico and West Texas to a tertiary university hospital. Retrospective data was obtained from chart review based on referrals made to the Southwest Cancer Center in Lubbock, TX for abnormal complete blood count or coagulation tests. Necessity of referrals were assessed according to patient laboratory values before referral, at initial visit, and whether therapy was started by the primary care physician (PCP). One hundred one patients met the study criteria during the period in review. The most common reasons of referral were iron deficiency anemia, leukopenia or leukocytosis and other types of anemia. About 33% of the referrals were determined to be manageable by a PCP as either the correct therapy had been already started before referral and/or the laboratory values were back to normal at the time of the first subspecialty visit. The total estimated cost of unnecessary referrals, including clinic visits and laboratories were $82,888 excluding mileage costs, days of work-school missed, and child care. Incorporation of referral guidelines, improving communication between PCP and subspecialties, and utilizing age-sex appropriate values in the interpretation of results could prevent excessive subspecialty referrals.

Objective: Identify a plasma-based activity, or biomarker, that defines the mechanism(s) by which Covid-19 disease triggers excessive coagulation.

Hemophagocytic lymphohistiocytosis (HLH) is a syndrome characterized by a hyperinflammatory state due to an aberrant activation of the immune cells. It can be familial or secondary to malignancy, autoimmune or metabolic diseases. Most HLH cases are triggered by infection. Histiocyte society suggested HLH-2004 protocol for diagnosis and treatment of both forms. Here, we present a three-year-old girl with B-cell acute lymphoblastic leukemia who developed HLH secondary to cytomegalovirus infection during maintenance therapy. She was successfully treated without needing full HLH protocol therapy. We discuss modified therapy for this specific group of HLH, summarizing 5 other similar cases in the literature.

Introduction: Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening syndrome characterized by a reactive process resulting from prolonged and excessive activation of immune cells that can be genetic or secondary to underlying conditions such as autoimmunity and malignancy. Here, we present a pediatric acute leukemia patient who presented with febrile neutropenia and was found to have Cytomegalovirus (CMV) induced HLH. Case report: A three-year-old girl with high risk precursor B-cell acute lymphoblastic leukemia (B-ALL) in maintenance therapy was admitted for evalaution of febrile neutropenia. …

Conclusions Hemophagocytic lymphohistiocytosis (HLH) is a clinical syndrome of multisystem inflammatory response with poor outcome if not diagnosed and treated early. Although Cytomegalovirus (CMV) disease is rare in non-transplant children with acute lymphoblastic leukaemia (ALL), it can lead to HLH in the setting of immunosuppression. We hereby describe a paediatric ALL patient, presenting with prolonged fever and pancytopenia who was found to have HLH triggered by acute CMV infection. A three-year-old girl with high risk precursor B-ALL was admitted with febrile neutropenia during maintenance therapy. She had fever for two days without any other associated symptoms. Her physical exam was unremarkable other than petechiae and hepatosplenomegaly. The complete blood count on admission showed pancytopenia. Cefepime was started empirically after blood cultures were drawn. The bone marrow biopsy was done as the fever persisted which revealed occasional hemophagocytosis without any blasts. She was diagnosed with HLH as she fulfilled the 6 of 8 criteria including phagocytosis, fever, splenomegaly, cytopenia, hyperferritinemia of 18,783 ng/mL and hypertriglyceridemia. She was started on prednisone at 1 mg/kg/day, which was increased due to recurrence of fever with increased ferritin levels. Soluble IL-2 receptor was also above diagnostic levels. Microbiologic tests for the underlying cause of HLH revealed >2 million IU/mL of CMV PCR. Ganciclovir was started and two days later fever resolved. Eye exam was negative for retinitis. She was discharged home on oral valganciclovir and completed total four weeks of antiviral therapy. On her last follow-up, three months after discharge, her CMV PCR was undetectable, ferritin levels were downtrending and she continued the maintenance chemotherapy. There are only five cases similar to our patient in the literature that were shown to have CMV-induced HLH in paediatric ALL. All of them were treated with antiviral therapy, while in two cases steroids and in one also intravenous immunoglobulin were given. In conclusion, we suggest that antiviral therapy in addition to HLH treatment should be considered until CMV viremia is undetectable. As CMV-induced HLH is a rare phenomenon in non-transplant ALL patients, genetic testing can be performed for a possible predisposition.

Background: Therapy discontinuations and toxicities occur because of significant interindividual variations in 6-mercaptopurine (6-MP) and methotrexate (MTX) response during maintenance therapy of childhood acute lymphoblastic leukemia (ALL). 6-MP/MTX intolerance in some of the patients cannot be explained by thiopurine S-methyl transferase (TPMT) gene variants. In this study, we aimed to investigate candidate pharmacogenetic determinants of 6-MP and MTX intolerance in Turkish ALL children. Methods: In total, 48 children with ALL who had completed or were receiving maintenance therapy according to Children’s Oncology Group (COG) protocols were enrolled. Fifteen single-nucleotide polymorphisms in 8 candidate genes that were related to drug toxicity or had a role in the 6-MP/MTX metabolism (TPMT, ITPA, MTHFR, IMPDH2, PACSIN2, SLCO1B1, ABCC4, and PYGL) were genotyped by competitive allele-specific PCR (KASP). Drug doses during maintenance therapy were modified according to the protocol. Results: The median drug dose intensity was 50% (28% to 92%) for 6-MP and 58% (27% to 99%) for MTX in the first year of maintenance therapy, which were lower than that scheduled in all patients. Among the analyzed polymorphisms, variant alleles in SLCO1B1 rs4149056 and rs11045879 were found to be associated with lower 6-MP/MTX tolerance. Conclusions: SLCO1B1 rs4149056 and rs11045879 polymorphisms may be important genetic markers to individualize 6-MP/MTX doses.