Treatment of newly diagnosed severe aplastic anemia in children: Evidence-based recommendations.

Severe aplastic anemia (SAA) is a rare potentially fatal hematologic disorder. Although overall outcomes with treatment are excellent, there are variations in management approach, including differences in treatment between adult and pediatric patients. Certain aspects of treatment are under active investigation in clinical trials. Because of the rarity of the disease, some pediatric hematologists may have relatively limited experience with the complex management of SAA. The following recommendations reflect an up-to-date evidence-based approach to the treatment of children with newly diagnosed SAA.

Treatment of relapsed/refractory severe aplastic anemia in children: Evidence-based recommendations.

Severe aplastic anemia (SAA) is a rare potentially fatal hematologic disorder. Although overall outcomes with treatment are excellent, there are variations in management approach, including differences in treatment between adult and pediatric patients. Certain aspects of treatment are under active investigation in clinical trials. Because of the rarity of the disease, some pediatric hematologists may have relatively limited experience with the complex management of SAA. The following recommendations reflect an up-to-date evidence-based approach to the treatment of children with relapsed or refractory SAA.

Abnormal SCID Newborn Screening and Spontaneous Recovery Associated with a Novel Haploinsufficiency IKZF1 Mutation.

PURPOSE: IKAROS, encoded by IKZF1, is a member of the IKAROS family of zinc-finger transcription factors playing critical roles in lymphocyte development, differentiation, and tumor suppression. Several studies demonstrated that IKZF1 mutations affecting DNA binding or homo-/hetero-dimerization are mostly associated with common variable immunodeficiency, combined immunodeficiency, or hematologic manifestations. Herein we report a likely de novo, nonsense IKZF1 mutation (p.C182*) in a baby with low T cell receptor excision circles (TREC) identified by newborn screening testing for severe combined immunodeficiency. The patient also presented a profound B cell deficiency at birth. METHODS: Genetic, functional, immunologic, and clinical outcome data associated with this patient and her mutation were evaluated. RESULTS: Mutant p.C182* was detected in the cytoplasm of the patient's primary cells, in contrast to wild type (WT) IKAROS protein, only detected in the nucleus. Functional in vitro assessments revealed that p.C182* was less stable than WT IKAROS protein and failed to bind to its target DNA binding sequence and dimerize with WT IKAROS protein, resulting in impaired pericentromeric targeting and transcriptional repression by means of haploinsufficiency. During follow-up, while a spontaneous recovery of TREC and T cells was observed, B cells improved but not to sustained normal ranges. CONCLUSIONS: Patients with IKAROS-associated diseases can present with SCID-like TREC values through newborn screening testing. IKZF1 mutations should be added to the low TREC differential, although spontaneous recovery has to be considered.

Endothelial injury, F-actin and vitamin-D binding protein after hematopoietic stem cell transplant and association with clinical outcomes.

Endothelial injury after hematopoietic stem cell transplant is an important initiating factor for early transplant toxicities of thrombotic microangiopathy and acute graft versus host disease. We hypothesized that release of the angiopathic molecule filamentous actin from hematopoietic cells lysed during conditioning prior to stem cell transplant would be associated with clinical outcomes. We detected filamentous actin in the blood of 52% of stem cell transplant recipients in the first 14 days after transplant, and children with detectable filamentous actin had significantly elevated risk of thrombotic microangiopathy (p= 0.03) and non-relapse mortality (p= 0.04). Filamentous actin is cleared from the circulation by vitamin D binding protein so we expected that higher levels of vitamin D binding protein would improve outcomes. In a cohort of 190 children receiving allogeneic transplant, risk of thrombotic microangiopathy was reduced in those with serum concentrations of vitamin D binding protein above the median at day 30 (10% vs 31%, p=0.01), and graft versus host disease and non-relapse mortality were reduced in those with levels above the median at day 100 (3% vs 18%, p=0.04 and 0% vs 15%, p=0.002). Western blot analyses demonstrated actin-vitamin D binding protein complexes in the blood, which cleared by day 21-28. Our data support modulation of cytokine secretion and macrophage phenotype by vitamin D binding protein later after transplant. Taken together, our data identify an association between filamentous-actin, a mediator of endothelial damage, and vitamin D binding protein, an actin scavenger, as modifiers of risk of clinical consequences of endothelial injury.

Comparison of total body irradiation versus non-total body irradiation containing regimens for de novo acute myeloid leukemia in children.

With limited data comparing hematopoietic cell transplant outcomes between myeloablative total body irradiation (TBI) containing and non-TBI regimens in children with de novo acute myeloid leukemia, the aim of this study was to compare transplant-outcomes between these regimens. Cox regression models were used to compare transplant-outcomes after TBI and non-TBI regimens in 624 children transplanted between 2008 and 2016. Thirty two percent (n=199) received TBI regimens whereas 68% (n=425) received non-TBI regimens. Five-year non-relapse mortality was higher with TBI regimens (22% vs. 11%, p<0.0001) but relapse was lower (23% vs. 37%, p<0.0001) compared to non-TBI regimens. Consequently, overall (62% vs. 60%, p=1.00) and leukemia-free survival (55% vs. 52%, p=0.42) did not differ between treatment groups. Grade II-IV acute GVHD was higher with TBI regimens (56% vs. 27%, p<0.0001) but not chronic GVHD. The 3-year incidence of gonadal or growth hormone deficiency was higher with TBI regimens (24% vs. 8%, p<0.001) but there were no differences in late pulmonary, cardiac or renal impairment. In the absence of a survival advantage, the choice of TBI or non-TBI regimen merits careful consideration with the data favoring non-TBI regimens to limit the burden of morbidity associated with endocrine dysfunction.

Diagnostic work-up for severe aplastic anemia in children: Consensus of the North American Pediatric Aplastic Anemia Consortium.

The North American Pediatric Aplastic Anemia Consortium (NAPAAC) is a group of pediatric hematologist-oncologists, hematopathologists, and bone marrow transplant physicians from 46 institutions in North America with interest and expertise in aplastic anemia, inherited bone marrow failure syndromes, and myelodysplastic syndromes. The NAPAAC Bone Marrow Failure Diagnosis and Care Guidelines Working Group was established with the charge of harmonizing the approach to the diagnostic workup of aplastic anemia in an effort to standardize best practices in the field. This document outlines the rationale for initial evaluations in pediatric patients presenting with signs and symptoms concerning for severe aplastic anemia.

Hematopoietic stem cell transplant for erythropoietic porphyrias in pediatric patients.

Cutaneous, hematopoietic, and hepatic manifestations of congenital erythropoietic porphyria (CEP) and erythropoietic protoporphyria (EPP) can be debilitating. We present our institution's experience with five patients with porphyria who underwent hematopoietic stem cell transplant (HSCT). Four patients with CEP, including three under age 2, received myeloablation. One patient with EPP, with prior liver transplant, received reduced intensity conditioning (RIC). Four patients are alive without porphyria symptomology and with full donor chimerism. HSCT corrects the defective heme pathway and should be considered early in patients with severe erythropoietic porphyrias to minimize end-organ damage. RIC regimens can minimize toxicity in patients with comorbidities.

Irradiation-free RIC HSCT has a tolerable safety profile and is effective therapy for pediatric bone marrow failure syndromes.

For patients with bone marrow failure syndromes (BMFS) who may tolerate gradual donor engraftment and achieve adequate disease control with stable mixed chimerism, RIC regimens may be preferable to myeloablative regimens. We performed a retrospective analysis of outcomes for patients who underwent HSCT at our institution between 2009 and 2017 for BMFS using an irradiation-free RIC regimen. Fourteen pediatric patients with BMFS received fludarabine (30 mg/m2 IV daily × 3), thiotepa (5 mg/kg IV every 12 hours × 2), and melphalan (70 mg/m2 IV daily × 2) prior to HSCT. Our cohort included the following diagnoses: SAA (n = 7), CAMT (n = 4), SCN (n = 1), DBA (n = 1), and non-Fanconi congenital BMF (n = 1). Seven patients underwent a MSD transplant; seven underwent an unrelated donor transplant. All patients are alive with median follow-up of 1112 days (range 455-2549 days). The median time to neutrophil engraftment was 16 days (range 10-26 days). All were transfusion independent by day + 100. The highest grade of aGVHD was grade 2; 8 (57%) did not develop aGVHD. Four (28.5%) developed extensive cGVHD, 4 (28.5%) developed limited cGVHD, and 6 (43%) did not develop cGVHD. No patients developed SOS. None died from GVHD or infectious complications. HSCT with RIC with fludarabine, thiotepa, and melphalan for BMFS was effective with a tolerable safety profile. Probability of OS at 100 days and 1 year was 100%.

Thinking Beyond HLH: Clinical Features of Patients with Concurrent Presentation of Hemophagocytic Lymphohistiocytosis and Thrombotic Microangiopathy.

Hemophagocytic lymphohistiocytosis (HLH) is a syndrome of excessive immune system activation driven mainly by high levels of interferon gamma. The clinical presentation of HLH can have considerable overlap with other inflammatory conditions. We present a cohort of patients with therapy refractory HLH referred to our center who were found to have a simultaneous presentation of complement-mediated thrombotic microangiopathy (TMA). Twenty-three patients had therapy refractory HLH (13 primary, 4 EVB-HLH, 6 HLH without known trigger). Sixteen (69.6%) met high-risk TMA criteria. Renal failure requiring renal replacement therapy, severe hypertension, serositis, and gastrointestinal bleeding were documented only in patients with HLH who had concomitant complement-mediated TMA. Patients with HLH and without TMA required ventilator support mainly due to CNS symptoms, while those with HLH and TMA had respiratory failure predominantly associated with pulmonary hypertension, a known presentation of pulmonary TMA. Ten patients received eculizumab for complement-mediated TMA management while being treated for HLH. All patients who received the complement blocker eculizumab in addition to the interferon gamma blocker emapalumab had complete resolution of their TMA and survived. Our observations suggest co-activation of both interferon and complement pathways as a potential culprit in the evolution of thrombotic microangiopathy in patients with inflammatory disorders like refractory HLH and may offer novel therapeutic approaches for these critically ill patients. TMA should be considered in children with HLH and multi-organ failure, as an early institution of a brief course of complement blocking therapy in addition to HLH-targeted therapy may improve clinical outcomes in these patients.

Circulating dsDNA, endothelial injury, and complement activation in thrombotic microangiopathy and GVHD.

Transplant-associated thrombotic microangiopathy (TA-TMA) is a common and poorly recognized complication of hematopoietic stem cell transplantation (HSCT) associated with excessive complement activation, likely triggered by endothelial injury. An important missing piece is the link between endothelial injury and complement activation. We hypothesized that neutrophil extracellular traps (NETs) mechanistically link endothelial damage with complement activation and subsequent TA-TMA. Neutrophil activation releases granule proteins together with double-stranded DNA (dsDNA) to form extracellular fibers known as NETs. NETs have been shown to activate complement and can be assessed in humans by quantification of dsDNA in serum. We measured levels of dsDNA, as a surrogate for NETs in 103 consecutive pediatric allogeneic transplant recipients at day 0, +14, +30, +60, and +100. A spike in dsDNA production around day +14 during engraftment was associated with subsequent TA-TMA development. Peak dsDNA production around day +14 was associated with interleukin-8-driven neutrophil recovery. Increased dsDNA levels at days +30, +60, and +100 were also associated with increased mortality and gastrointestinal graft-versus-host disease (GVHD). NETs may serve as a mechanistic link between endothelial injury and complement activation. NET formation may be one mechanism contributing to the clinical overlap between GVHD and TA-TMA.

Combination of High-Dose Methylprednisolone and Defibrotide for Veno-Occlusive Disease in Pediatric Hematopoietic Stem Cell Transplant Recipients.

Veno-occlusive disease (VOD) is a serious complication of hematopoietic stem cell transplant (HSCT), with high mortality in severe cases and until recently very limited therapeutic options consisting largely of supportive care. Defibrotide was recently approved in the United States for the treatment of severe VOD in patients with renal or pulmonary dysfunction after HSCT. Our group previously published on the use of high-dose methylprednisolone (500 mg/m2 per dose every 12 hours for 6 doses) in patients with VOD, showing good success. A small subset of these individuals were also treated with defibrotide, but additional studies using the combination of high-dose methylprednisolone and defibrotide for the treatment of VOD are lacking. We present a single-institution retrospective chart review of 15 HSCT patients with VOD treated with the combination of high-dose methylprednisolone and defibrotide. VOD developed at a median of 17 days post-HSCT, and combination therapy was initiated within 1 day of VOD diagnosis. Twelve of 15 patients (80%) had multiorgan failure. Our single-center experience using both high-dose methylprednisolone and defibrotide showed a day +100 survival rate of 73% and an overall VOD complete resolution rate of 66.7%, higher than the rates reported in the recent literature using defibrotide alone (40% to 50% day +100 overall survival). These data suggest that the combination of high-dose steroids and defibrotide may be superior to defibrotide alone and warrant further investigation.

Proinflammatory Dual Receptor T Cells in Chronic Graft-versus-Host Disease.

Defective post-transplantation thymopoiesis is associated with chronic graft-versus-host disease (GVHD), a multiorgan pathology affecting up to 80% of patients after allogeneic hematopoietic stem cell transplantation (HSCT). Previous work demonstrated that the subset of T cells expressing 2 T cell receptors (TCRs) is predisposed to alloreactivity, driving selective and disproportionate activity in acute GVHD in both mouse models and HSCT patients. Here we investigate a potential role for this pathogenic T cell subset in chronic GVHD (cGVHD). HSCT patients with cGVHD demonstrated increased numbers of dual TCR cells in circulation. These dual receptor cells had an activated phenotype, indicating an active role in cGVHD. Notably, single-cell RNA sequencing identified the increased dual TCR cells in cGVHD as predominantly expressing Tbet, indicative of a proinflammatory phenotype. These results identify dual TCR cells as specific mediators of pathogenic inflammation underlying cGVHD and highlight Tbet-driven T cell function as a potential pathway for potential therapeutic targeting.

Fertility Potential and Gonadal Function in Survivors of Reduced-Intensity Hematopoietic Stem Cell Transplantation.

The use of reduced-intensity conditioning (RIC) regimens has increased in an effort to minimize hematopoietic stem cell transplantation (HCT) end-organ toxicity, including gonadal toxicity. We aimed to describe the incidence of fertility potential and gonadal function impairment in adolescent and young adult survivors of HCT and to identify risk factors (including conditioning intensity) for impairment. We performed a multi-institutional, international retrospective cohort study of patients age 10 to 40 years who underwent first allogeneic HCT before December 1, 2019, and who were alive, in remission, and available for follow-up at 1 to 2 years post-HCT. For females, an AMH level of ≥.5 ng/mL defined preserved fertility potential; an AMH level of ≥.03 ng/mL was considered detectable. Gonadal failure was defined for females as an elevated follicle-stimulating hormone (FSH) level >30 mIU/mL with an estradiol (E2) level <17 pg/mL or current use of hormone replacement therapy (regardless of specific indication or intent). For males, gonadal failure was defined as an FSH level >10.4 mIU/mL or current use of hormone replacement therapy. A total of 326 patients (147 females) were available for analysis from 17 programs (13 pediatric, 4 adult). At 1 to 2 years post-HCT, 114 females (77.6%) had available FSH and E2 levels and 71 (48.3%) had available AMH levels. FSH levels were reported for 125 males (69.8%). Nearly all female HCT recipients had very low levels of AMH. One of 45 (2.2%) recipients of myeloablative conditioning (MAC) and four of 26 (15.4%) recipients of reduced-intensity conditioning (RIC) (P = .06) had an AMH ≥.5 ng/m, and 8 of 45 MAC recipients (17.8%) and 12 of 26 RIC recipients (46.2%) (P = .015) had a detectable AMH level. Total body irradiation (TBI) dose and cyclophosphamide equivalent dose (CED) were not associated with detectable AMH. The incidence of female gonadal hormone failure was 55.3%. In univariate analysis, older age at HCT was associated with greater likelihood of gonadal failure (median age, 17.6 versus 13.9; P < .0001), whereas conditioning intensity (RIC versus MAC), TBI, chronic graft-versus-host disease requiring systemic therapy, and CED were not significantly associated with gonadal function. In multivariable analysis, age remained statistically significant (odds ratio [OR]. 1.11; 95% confidence interval [CI], 1.03 to 1.22) for each year increase; P = .012), Forty-four percent of the males had gonadal failure. In univariate analysis, older age (median, 16.2 years versus 14.4 years; P = .0005) and TBI dose (P = .002) were both associated with gonadal failure, whereas conditioning intensity (RIC versus MAC; P = .06) and CED (P = .07) were not statistically significant. In multivariable analysis, age (OR, 1.16; 95% CI, 1.06-1.27 for each year increase; P = .0016) and TBI ≥600 cGy (OR, 6.23; 95% CI, 2.21 to 19.15; P = .0008) remained significantly associated with gonadal failure. Our data indicate that RIC does not significantly mitigate the risk for gonadal failure in females or males. Age at HCT and (specifically in males) TBI use seem to be independent predictors of post-transplantation gonadal function and fertility status. All patients should receive pre-HCT infertility counseling and be offered appropriate fertility preservation options and be screened post-HCT for gonadal failure.

Liver disease and transplantation in telomere biology disorders: An international multicenter cohort.

BACKGROUND: Patients with telomere biology disorders (TBD) develop hepatic disease, including hepatitis, cirrhosis, and hepatopulmonary syndrome. No specific treatment exists for TBD-related liver disease, and the role of liver transplantation (LT) remains controversial. Our study objectives were to describe the clinical characteristics, management, and outcomes in patients with TBD-related liver disease, and their LT outcomes. METHODS: Data from 83 patients with TBD-associated liver disease were obtained from 17 participating centers in the Clinical Care Consortium of Telomere-Associated Ailments and by self-report for our retrospective, multicenter, international cohort study. RESULTS: Group A ("Advanced") included 40 patients with advanced liver disease. Of these, 20 underwent LT (Group AT). Group M ("Mild") included 43 patients not warranting LT evaluation, none of whom were felt to be medically unfit for liver transplantation. Supplemental oxygen requirement, pulmonary arteriovenous malformation, hepatopulmonary syndrome, and higher bilirubin and international normalized ratio values were associated with Group A. Other demographics, clinical manifestations, and laboratory findings were similar between groups. Six group A patients were declined for LT; 3 died on the waitlist. Median follow-up post-LT was 2.9 years (range 0.6-13.2 y). One-year survival post-LT was 73%. Median survival post-LT has not been reached. Group AT patients had improved survival by age compared to all nontransplant patients (log-rank test p = 0.02). Of 14 patients with pretransplant hypoxemia, 8 (57%) had improved oxygenation after transplant. CONCLUSIONS: LT recipients with TBD do not exhibit excessive posttransplant mortality, and LT improved respiratory status in 57%. A TBD diagnosis should not exclude LT consideration.

Chronic active Epstein-Barr virus and hydroa vacciniforme-like lymphoproliferative disorder in a pediatric patient complicated by fatal ruptured cerebral artery aneurysm.

Hydroa vacciniforme-like lymphoproliferative disorder (HV-LPD) is a rare cutaneous form of chronic active Epstein-Barr virus (CAEBV) that presents with vesicular lesions induced by sun-exposure. Arterial aneurysm is a rare but potentially fatal complication of CAEBV and HV-LPD.

A pragmatic multi-institutional approach to understanding transplant-associated thrombotic microangiopathy after stem cell transplant.

Transplant-associated thrombotic microangiopathy (TA-TMA) is a severe complication of hematopoietic stem cell transplantation (HSCT). A single-center prospective screening study has shown that the incidence of TA-TMA is much higher than prior retrospective studies that did not systematically screen. These data have not been replicated in a multicenter study. Our objective was to determine the incidence and risk factors for TA-TMA and compare outcomes of pediatric HSCT patients with and without TA-TMA. Patients were prospectively screened for TA-TMA at participating centers using a simple to implement and inexpensive strategy from the start of the preparative regimen through day +100. TA-TMA was diagnosed if ≥4 of 7 laboratory/clinical markers diagnostic for TA-TMA were present concurrently or if tissue histology showed TA-TMA. A total of 614 patients (359 males; 58%) received prospective TA-TMA screening at 13 pediatric centers. TA-TMA was diagnosed in 98 patients (16%) at a median of 22 days (interquartile range, 14-44) posttransplant. Patients with TA-TMA had significantly increased bloodstream infections (38% [37/98] vs 21% [107/51], P ≤ .001), mean total hospitalization days (68; 95% confidence interval [CI], 63-74 vs 43; 95% CI, 41-45; P ≤ .001), and number of days spent in the intensive care unit (10.1; 95% CI, 6.4-14; vs 1.6; 95% CI, 1.1-2.2; P ≤ .001) in the first 100 days after HSCT compared with patients without TA-TMA. Overall survival was significantly higher in patients without TA-TMA (93%; 490/516) compared with patients with TA-TMA (78%; 76/98) (P ≤ .001). These data support the need for systematic screening for TA-TMA and demonstrate the feasibility and efficacy of an easy to implement strategy to do so.