Survey of pediatric transplant center practices regarding COVID-19 vaccine mandates for transplant candidates and living donors and use of COVID-19-positive deceased organs.

BACKGROUND: COVID-19 vaccine is recommended for individuals ages ≥6 months; however, whether vaccination should be mandated for transplant candidates and living donors remains controversial. This study assessed COVID-19 policies at US pediatric solid organ transplant centers. METHODS: A 79-item survey was emailed between March and April 2022 to 200 UNOS Medical Directors detailing center COVID-19 vaccine policies for transplant candidates and living donors and use of grafts from COVID-19-positive deceased donors. RESULTS: The response rate was 77% (154/200). For children aged 5-15 years, 23% (35/154 centers) have a COVID-19 vaccine mandate, 27% (42/154) anticipate implementing a future mandate, and 47% (72/154) have not considered or do not anticipate implementing a mandate. For children ≥16 years, 32% (50/154 centers) have a COVID-19 vaccine mandate, 25% (39/154) anticipate implementing a future mandate, and 40% (62/154) have not considered or do not anticipate implementing a mandate. The top two reasons for not implementing a COVID-19 vaccine mandate were concerns about penalizing a child for their parent's decision and worsening inequities in transplant. Of 85 kidney and liver living donor centers, 32% (27/85) require vaccination of donors. Twenty percent (31/154) of centers accept organs from COVID-19-positive deceased donors. CONCLUSIONS: There is great variation among pediatric SOT centers in both the implementation and details of COVID-19 vaccine mandates for candidates and living donors. To guide more uniform policies, further data are needed on COVID-19 disease, vaccine efficacy, and use of grafts from donors positive for COVID-19 in the pediatric transplant population.

The learning health system for pediatric nephrology: building better systems to improve health.

Learning health systems (LHS) align science, informatics, incentives, and culture for continuous improvement and innovation. In this organizational system, best practices are seamlessly embedded in the delivery process, and new knowledge is captured as an integral byproduct of the care delivery experience aimed to transform clinical practice and improve patient outcomes. The objective of this review is to describe how building better health systems that integrate clinical care, improvement, and research as part of an LHS can improve care within pediatric nephrology. This review will provide real-world examples of how this system can be established in a single center and across multiple centers as learning health networks.

A Medication Adherence Promotion System to Reduce Late Kidney Allograft Rejection: A Quality Improvement Study.

RATIONALE & OBJECTIVE: Adolescent and young adult kidney transplant recipients have a high risk of rejection related to suboptimal adherence. Multicomponent interventions improve adherence in controlled trials, but clinical implementation is lacking. We describe an initiative to reduce allograft rejection using evidence-based adherence promotion strategies. STUDY DESIGN: Interrupted time series. SETTING & PARTICIPANTS: Kidney transplant recipients cared for at Cincinnati Children's Hospital ≥ 1 year after transplant and taking ≥1 immunosuppressive medication(s) from 2014 through 2017. QUALITY IMPROVEMENT ACTIVITIES: The following interventions, collectively called MAPS (Medication Adherence Promotion System), were implemented over 14 months: (1) adherence promotion training for clinical staff, 2) electronic health record-supported adherence risk screening, (3) systematic assessment of medication adherence barriers, (4) designation of specific staff to address adherence barriers, (5) shared decision-making with the patients to overcome adherence barriers, (6) follow-up evaluation to assess progress, and (7) optional electronic medication monitoring. OUTCOMES: Primary Outcome: Late acute rejection. Process measures were conducted to assess barriers, identify barriers, and perform interventions. The secondary outcomes/balancing measures were de novo donor-specific antibodies (DSA), biopsy rate, and rejections per biopsy. ANALYTICAL APPROACH: Time series analysis using statistical process control evaluated patient-days between acute rejections as well as monthly rejections per 100 patient-months before and after implementation. To control for known rejection risk factors including changes in treatment and case mix, multivariable analyses were performed. RESULTS: The monthly rejection rate fell from 1.61 rejections per 100 patient-months in the 26 months before implementation to 0.88 rejections per 100 patient-months in the 22 months after implementation. In the multivariable analysis, MAPS was associated with a 50% reduction in rejection incidence (incidence rate ratio, 0.50 [95% CI, 0.27-0.91]; P = 0.02). DSA and time since transplant (per each additional year) were also associated with rejection incidence (incidence rate ratio, 2.27 [P = 0.02] and 0.87 [P = 0.02], respectively). LIMITATIONS: Single-center study, and potential confounding by unmeasured variables. CONCLUSIONS: Clinical implementation of evidence-based adherence-promotion strategies was associated with a 50% reduction in acute rejection incidence over 2 years.

COVID-19 in pediatric kidney transplantation: The Improving Renal Outcomes Collaborative.

There are limited data on the impact of COVID-19 in children with a kidney transplant (KT). We conducted a prospective cohort study through the Improving Renal Outcomes Collaborative (IROC) to collect clinical outcome data about COVID-19 in pediatric KT patients. Twenty-two IROC centers that care for 2732 patients submitted testing and outcomes data for 281 patients tested for SARS-CoV-2 by PCR. Testing indications included symptoms and/or potential exposures to COVID-19 (N = 134, 47.7%) and/or testing per hospital policy (N = 154, 54.8%). Overall, 24 (8.5%) patients tested positive, of which 15 (63%) were symptomatic. Of the COVID-19-positive patients, 16 were managed as outpatients, six received non-ICU inpatient care and two were admitted to the ICU. There were no episodes of respiratory failure, allograft loss, or death associated with COVID-19. To estimate incidence, subanalysis was performed for 13 centers that care for 1686 patients that submitted all negative and positive COVID-19 results. Of the 229 tested patients at these 13 centers, 10 (5 asymptomatic) patients tested positive, yielding an overall incidence of 0.6% and an incidence among tested patients of 4.4%. Pediatric KT patients in the United States had a low estimated incidence of COVID-19 disease and excellent short-term outcomes.

Impact of once-daily ER-Tac on trough concentration variability in a stable AYA renal transplant recipient cohort.

BACKGROUND: Successful renal transplantation requires complex medication regimens that rely on strict adherence to be effective. Variability in immunosuppression exposure, specifically tacrolimus, is associated with poor allograft outcomes. Wide intra-patient variability of tacrolimus trough concentrations (Vtac) is likely, in part, attributable to regimen complexity and poor medication adherence. Once-daily tacrolimus formulations create opportunity to simplify therapeutic regimens, and this study aims to evaluate their impact on Vtac and ultimately transplant outcomes. METHODS: This retrospective cohort study investigated stable (AYA) renal transplant recipients converted from (IR-Tac) to (ER-Tac). Subjects served as their own controls. Vtac was assessed by measuring the (SD) of serial tacrolimus trough concentrations prior to and at four time points post-conversion to ER-Tac over 24-month follow-up. Secondary outcome measures included graft function, infection rates, and effect on modifiable treatment-related factors. RESULTS: Twenty-eight AYA subjects were converted from IR-Tac to ER-Tac. Vtac significantly improved following conversion and was sustained for 24 months (Vtac0 2.32 vs. Vtac24 1.11, p .017). Renal function remained stable, and (BPAR) rates were modest (14%). Mean pill burden was reduced by 15%, and 42.9% of subjects achieved a once-daily medication regimen. CONCLUSIONS: Conversion from IR-Tac to ER-Tac in this AYA population significantly improved Vtac with sustained effect over 2 years. This effect is likely attributable in part to simplification of the medication regimen and presumably improved medication adherence. Such conversion does not appear to compromise graft function for at least 2 years post-conversion.

Management of dyslipidemia in pediatric renal transplant recipients.

Dyslipidemia after kidney transplantation is a common complication that has historically been underappreciated, especially in pediatric recipients. It is also a major modifiable risk factor for cardiovascular disease, a top cause of morbidity and mortality of transplant patients. While most knowledge about post-transplant dyslipidemia has been generated in adults, recommendations and treatment strategies also exist for children and are presented in this review. Awareness of these applicable guidelines and approaches is required, but not sufficient, for the reliable management of dyslipidemia in our patients, and additional needs and opportunities for comprehensive care in this area (e.g., quality improvement) are outlined.

Pediatric trichodysplasia spinulosa: A report of 2 cases and review of the literature.

Trichodysplasia spinulosa is a rare disorder caused by the ubiquitous trichodysplasia spinulosa-associated polyomavirus (TSPyV) and characterized clinically by predominately centrofacial, but often generalized, folliculocentric papules with protuberant keratinaceous spines. Although seroprevalence reaches up to 70% in adult populations, TSPyV causes clinical manifestations in a small percentage of patients who are immunosuppressed. Diagnosis can be made using typical clinical and histologic features, SV40T antibody immunostaining, and PCR of various tissues including the keratinaceous spine, skin, serum, urine, and CSF. Various topical and systemic medications have demonstrated variable success. Decreasing or discontinuing immunosuppression has also been shown to improve or alleviate clinical manifestations.

Composite Health Outcomes in Pediatric and Young Adult Kidney Transplant Recipients.

OBJECTIVE: To assess composite health outcomes in pediatric and young adult kidney transplant recipients following kidney transplantation. STUDY DESIGN: We conducted a cross-sectional study of all recipients at our center who had a 1-, 3-, 5-, and/or 10-year transplant anniversary visit between October 2008 and February 2015. The kidney transplant recipients were assessed at each time point according to an outcome measure consisting of 15 pass/fail criteria in 5 domains: allograft health, rejection and immunology, infection, cardiovascular health, and growth. RESULTS: We analyzed 148 patients at 231 transplantation anniversary visit time points; 52 of 82 (63%) patients assessed at 1 year had an ideal outcome, meeting at least 13 of the 15 criteria. This decreased to 37% at year 3, 40% at year 5, and 26% at year 10 (P < .01). The most common failures across all time points occurred in the domains of growth (43%-52% passing) and cardiovascular health (33%-51% passing). Allograft health declined significantly, decreasing from 74% at year 1 to 33% at year 10 (P < .01). The percentage of patients with graft failure increased from 2.4% at 1 year to 39.5% at 10 years (P < .01), and patient deaths increased from 0 to 11% (P < .01) in the same time frame. CONCLUSIONS: Ideal outcomes for pediatric kidney transplant recipients decrease over time with growth, cardiovascular health, and allograft health as the primary failure modes. Understanding the composite health of young recipients will allow primary care providers and nephrologists alike to evaluate the overall health of kidney transplant recipients and focus clinical care on the most common sequelae.

Donor-specific antibodies in a pediatric kidney transplant population-Prevalence and association with antiproliferative drug dosing.

Prevalence and implications of anti-HLA class I and class II antibodies are beginning to be better characterized in pediatric kidney transplant recipients. dnDSA formation is predictive of AMR and downstream diminished graft function and survival. However, risk factors for the development of dnDSA are not well defined in this patient population. After introducing DSA surveillance into our pediatric kidney transplant program, we are reporting the prevalence of class I and class II DSA in 67 otherwise stable recipients. Secondary end-points included risk factors for DSA development and assessment of graft function. Significantly, lower median daily MMF doses were observed in patients with DSAs compared to patients without DSAs (371 vs 617 mg/m2 /d, respectively; P = 0.035). Class II DSA formation was more common, with a prevalence of 17.9%, as compared to 10.4% for class I DSA. Estimated glomerular filtration rate was also decreased in patients with positive DSA vs those with negative titers (71, SD 25 vs 78, SD 29 mL/min/1.73 m2 , respectively; P = 0.034). We conclude that reduced-dose MMF is associated with dnDSA and DSA is associated with diminished graft function in stable pediatric kidney transplant recipients.

IGG3 anti-HLA donor-specific antibodies and graft function in pediatric kidney transplant recipients.

Anti-HLA DSAs are associated with ABMR and graft loss in KT recipients, yet the influence of DSA IgG subclass on outcomes in pediatric KT recipients is not completely understood. We performed a single-center retrospective chart review of pediatric KT recipients with anti-HLA DSAs, aiming to study the association between specific DSA IgG subclasses and graft outcomes, including ABMR and significant graft dysfunction (graft loss or 50% decrease in eGFR). Thirty-six patients (mean age 15.4y) with DSAs initially detected 1 month-14.3 years post-transplantation were followed for a median of 2.8 years. Rates of IgG1, 2, 3, and 4 subclass detection were 92%, 33%, 58%, and 25%, respectively. Twenty-two patients (61%) had clinical ABMR, whereas 19% had subclinical ABMR, and 13 (36%) experienced significant graft dysfunction. Patients with IgG3+ DSAs had a higher risk of graft dysfunction compared with IgG3- patients (52% vs 13%, P = .03). In a multiple Cox proportional regression analysis, the presence of IgG3+ DSA was independently associated with significant graft dysfunction (HR 10.45, 95% CI 1.97-55.55, P = .006). In conclusion, IgG3 subclass DSAs are associated with graft dysfunction and may be useful for risk stratification and treatment decisions in DSA-positive pediatric KT recipients.

Adherence in pediatric kidney transplant recipients: solutions for the system.

Non-adherence remains a significant problem among pediatric (and adult) renal transplant recipients. Non-adherence among solid organ transplant recipients results in US$15-100 million annual costs. Estimates of non-adherence range from 30 to 70% among pediatric patients. Research demonstrates that a 10% decrement in adherence is associated with 8% higher hazard of graft failure and mortality. Focus has begun to shift from patient factors that impact adherence to the contributing healthcare and systems factors. The purpose of this review is to describe problems within the systems implicated in non-adherence and potential solutions that may be related to positive adherence outcomes. Systems issues include insurance and legal regulations, provider and care team barriers to optimal care, and difficulties with transitioning to adult care. Potential solutions include recognition of how systems can work together to improve patient outcomes through improvements in insurance programs, a multi-disciplinary care team approach, evidence-based medical management, pharmacy-based applications and interventions to simplify medication regimens, improved transition protocols, and telehealth/technology-based multi-component interventions. However, there remains a significant lack of reliability in the application of these potential solutions to systems issues that impact patient adherence. Future efforts should accordingly focus on these efforts, likely by leveraging quality improvement and related principles, and on the investigation of the efficacy of these interventions to improve adherence and graft outcomes.

Hyperchloremia is independently associated with mortality in critically ill children who ultimately require continuous renal replacement therapy.

BACKGROUND: The optimal fluid management in critically ill children is currently under investigation with several studies suggesting that hyperchloremia, chloride load, and the use of chloride-rich fluids contribute to worse outcomes. METHODS: This is a single-center retrospective cohort study of Pediatric Intensive Care Unit patients from 2008 to 2016 requiring continuous renal replacement therapy (CRRT). Patients were excluded if they had end-stage renal disease, a disorder of chloride transport, or concurrent provision of extracorporeal membrane oxygenation therapy. RESULTS: Patients (n = 66) were dichotomized into two groups (peak chloride (Cl) ≥ 110 mmol/L vs. peak Cl < 110 mmol/L prior to CRRT initiation). Hyperchloremia was present in 39 (59%) children. Baseline characteristics were similar between groups. Fluid overload at CRRT initiation was more common in patients with hyperchloremia (11.5% IQR 3.8-22.4) compared to those without (5.5% IQR 0.9-13.9) (p = 0.04). Mortality was significantly higher in patients with hyperchloremia (n = 26, 67%) compared to those without (n = 8, 29%) (p = 0.006). Patients with hyperchloremia had 10.9 times greater odds of death compared to those without hyperchloremia, after adjusting for percent fluid overload, PRISM III score, time to initiation of CRRT, height, and weight (95% CI 2.4 to 49.5, p = 0.002). CONCLUSIONS: Hyperchloremia is common among critically ill children prior to CRRT initiation. In this population, hyperchloremia is independently associated with mortality. Further studies are needed to determine the impact of hyperchloremia on all critically ill children and the impact of chloride load on outcomes.

COQ2 nephropathy: a treatable cause of nephrotic syndrome in children.

BACKGROUND: Nephrotic syndrome can be caused by a subgroup of mitochondrial diseases classified as primary coenzyme Q10 (CoQ10) deficiency. Pathogenic COQ2 variants are a cause of primary CoQ10 deficiency and present with phenotypes ranging from isolated nephrotic syndrome to fatal multisystem disease. CASE-DIAGNOSIS/TREATMENT: We report three pediatric patients with COQ2 variants presenting with nephrotic syndrome. Two of these patients had normal leukocyte CoQ10 levels prior to treatment. Pathologic findings varied from mesangial sclerosis to focal segmental glomerulosclerosis, with all patients having abnormal appearing mitochondria on kidney biopsy. In two of the three patients treated with CoQ10 supplementation, the nephrotic syndrome resolved; and at follow-up, both have normal renal function and stable proteinuria. CONCLUSIONS: COQ2 nephropathy should be suspected in patients presenting with nephrotic syndrome, although less common than disease due to mutations in NPHS1, NPHS2, and WT1. The index of suspicion should remain high, and we suggest that providers consider genetic evaluation even in patients with normal leukocyte CoQ10 levels, as levels may be within normal range even with significant clinical disease. Early molecular diagnosis and specific treatment are essential in the management of this severe yet treatable condition.

Assessing barriers to adherence in routine clinical care for pediatric kidney transplant patients.

Patient-identified barriers to immunosuppressive medications are associated with poor adherence and negative clinical outcomes in transplant patients. Assessment of adherence barriers is not part of routine post-transplant care, and studies regarding implementing such a process in a reliable way are lacking. Using the Model for Improvement and PDSA cycles, we implemented a system to identify adherence barriers, including patient-centered design of a barriers assessment tool, identification of eligible patients, clear roles for clinic staff, and creating a culture of non-judgmental discussion around adherence. We performed time-series analysis of our process measure. Secondary analyses examined the endorsement and concordance of adherence barriers between patient-caregiver dyads. After three methods of testing, the most reliable delivery system was an EHR-integrated tablet that alerted staff of patient eligibility for assessment. Barriers were endorsed by 35% of caregivers (n=85) and 43% of patients (n=60). The most frequently patient-endorsed barriers were forgetting, poor taste, and side effects. Caregivers endorsed forgetting and side effects. Concordance between patient-caregiver dyads was fair (k=0.299). Standardized adherence barriers assessment is feasible in the clinical care of pediatric kidney transplant patients. Features necessary for success included automation, redundant systems with designated staff to identify and mitigate failures, aligned reporting structures, and reliable measurement approaches. Future studies will examine whether barriers predict clinical outcomes (eg, organ rejection, graft loss).

Mycophenolate mofetil-related leukopenia in children and young adults following kidney transplantation: Influence of genes and drugs.

MMF is commonly prescribed following kidney transplantation, yet its use is complicated by leukopenia. Understanding the genetics mediating this risk will help clinicians administer MMF safely. We evaluated 284 patients under 21 years of age for incidence and time course of MMF-related leukopenia and performed a candidate gene association study comparing the frequency of 26 SNPs between cases with MMF-related leukopenia and controls. We matched cases by induction, steroid duration, race, center, and age. We also evaluated the impact of induction and SNPs on time to leukopenia in all cases. Sixty-eight (24%) patients had MMF-related leukopenia, of which 59 consented for genotyping and 38 were matched with controls. Among matched pairs, no SNPs were associated with leukopenia. With non-depleting induction, UGT2B7-900A>G (rs7438135) was associated with increased risk of MMF-related leukopenia (P = .038). Time to leukopenia did not differ between patients by induction agent, but 2 SNPs (rs2228075, rs2278294) in IMPDH1 were associated with increased time to leukopenia. MMF-related leukopenia is common after transplantation. UGT2B7 may influence leukopenia risk especially in patients without lymphocyte-depleting induction. IMPDH1 may influence time course of leukopenia after transplant.

Responsiveness of the PROMIS® measures to changes in disease status among pediatric nephrotic syndrome patients: a Midwest pediatric nephrology consortium study.

BACKGROUND: Nephrotic syndrome represents a condition in pediatric nephrology typified by a relapsing and remitting course, proteinuria and the presence of edema. The PROMIS measures have previously been studied and validated in cross-sectional studies of children with nephrotic syndrome. This study was designed to longitudinally validate the PROMIS measures in pediatric nephrotic syndrome. METHODS: One hundred twenty seven children with nephrotic syndrome between the ages of 8 and 17 years participated in this prospective cohort study. Patients completed a baseline assessment while their nephrotic syndrome was active, a follow-up assessment at the time of their first complete proteinuria remission or study month 3 if no remission occurred, and a final assessment at study month 12. Participants completed six PROMIS measures (Mobility, Fatigue, Pain Interference, Depressive Symptoms, Anxiety, and Peer Relationships), the PedsQL version 4.0, and two global assessment of change items. RESULTS: Disease status was classified at each assessment: nephrotic syndrome active in 100% at baseline, 33% at month 3, and 46% at month 12. The PROMIS domains of Mobility, Fatigue, Pain Interference, Depressive Symptoms, and Anxiety each showed a significant overall improvement over time (p < 0.001). When the PROMIS measures were compared to the patients' global assessment of change, the domains of Mobility, Fatigue, Pain Interference, and Anxiety consistently changed in an expected fashion. With the exception of Pain Interference, change in PROMIS domain scores did not correlate with changes in disease activity. PROMIS domain scores were moderately correlated with analogous PedsQL domain scores. CONCLUSION: This study demonstrates that the PROMIS Mobility, Fatigue, Pain Interference, and Anxiety domains are sensitive to self-reported changes in disease and overall health status over time in children with nephrotic syndrome. The lack of significant anchoring to clinically defined nephrotic syndrome disease active and remission status may highlight an opportunity to improve the measurement of HRQOL in children with nephrotic syndrome through the development of a nephrotic syndrome disease-specific HRQOL measure.

Variable Eculizumab Clearance Requires Pharmacodynamic Monitoring to Optimize Therapy for Thrombotic Microangiopathy after Hematopoietic Stem Cell Transplantation.

Thrombotic microangiopathy (TMA) after hematopoietic stem cell transplantation (HSCT) associated with terminal complement activation, as measured by elevated plasma terminal complement (sC5b-9) concentrations, has a very high mortality. The complement inhibitor eculizumab may be a therapeutic option for HSCT-associated TMA. We examined the pharmacokinetics and pharmacodynamics (PK/PD) of eculizumab in children and young adult HSCT recipients with TMA and activated complement to determine drug dosing requirements for future efficacy trials. We analyzed prospectively collected laboratory samples and clinical data from 18 HSCT recipients with high-risk TMA presenting with complement activation who were treated with eculizumab. We measured eculizumab serum concentrations, total hemolytic complement activity, and plasma sC5b-9 concentrations. Population PK/PD analyses correlated eculizumab concentrations with complement blockade and clinical response and determined interindividual differences in PK parameters. We also compared transplant survival in patients treated with eculizumab (n = 18) with patients with the same high-risk TMA features who did not receive any targeted therapy during a separate prospective observational study (n = 11). In the PK analysis, we found significant interpatient variability in eculizumab clearance, ranging from 16 to 237 mL/hr/70 kg in the induction phase. The degree of complement activation measured by sC5b-9 concentrations at the start of therapy, in addition to actual body weight, was a significant determinant of eculizumab clearance and disease response. Sixty-one percent of treated patients had complete resolution of TMA and were able to safely discontinue eculizumab without disease recurrence. Overall survival was significantly higher in treated subjects compared with untreated patients (56% versus 9%, P = .003). Complement blocking therapy is associated with improved survival in HSCT patients with high-risk TMA who historically have dismal outcomes, but eculizumab pharmacokinetics in HSCT recipients differ significantly from reports in other diseases like atypical hemolytic uremic syndrome and paroxysmal nocturnal hemoglobinuria. Our eculizumab dosing algorithm, including pr-treatment plasma sC5b-9 concentrations, patient's actual body weight, and the first eculizumab dose (mg), accurately determined eculizumab concentration-time profiles for HSCT recipients with high-risk TMA. This algorithm may guide eculizumab treatment and ensure that future efficacy studies use the most clinically appropriate and cost-efficient dosing schedules.

Diagnostic and risk criteria for HSCT-associated thrombotic microangiopathy: a study in children and young adults.

Transplant-associated thrombotic microangiopathy (TMA) leads to generalized endothelial dysfunction that can progress to multiorgan injury, and severe cases are associated with poor outcomes after hematopoietic stem cell transplantation (HSCT). Identifying patients at highest risk for severe disease is challenging. We prospectively evaluated 100 consecutive HSCT recipients to determine the incidence of moderate and severe TMA and factors associated with poor overall outcomes. Thirty-nine subjects (39%) met previously published criteria for TMA. Subjects with TMA had a significantly higher nonrelapse mortality (43.6% vs 7.8%, P < .0001) at 1 year post-HSCT compared with those without TMA. Elevated lactate dehydrogenase, proteinuria on routine urinalysis, and hypertension were the earliest markers of TMA. Proteinuria (>30 mg/dL) and evidence of terminal complement activation (elevated sC5b-9) in the blood at the time of TMA diagnosis were associated with very poor survival (<20% at 1 year), whereas all TMA subjects without proteinuria and a normal sC5b-9 serum concentration survived (P < .01). Based on these prospective observations, we conclude that severe TMA occurred in 18% of HSCT recipients in our cohort and propose an algorithm to identify the highest-risk patients who might benefit from prompt clinical interventions.

Abnormalities in the alternative pathway of complement in children with hematopoietic stem cell transplant-associated thrombotic microangiopathy.

Hematopoietic stem cell transplant (HSCT)-associated thrombotic microangiopathy (TMA) is a complication that occurs in 25% to 35% of HSCT recipients and shares histomorphologic similarities with hemolytic uremic syndrome (HUS) and thrombotic thrombocytopenic purpura (TTP). The hallmark of all thrombotic microangiopathies is vascular endothelial cell injury of various origins, resulting in microangiopathic hemolytic anemia, platelet consumption, fibrin deposition in the microcirculation, and tissue damage. Although significant advances have been made in understanding the pathogenesis of other thrombotic microangiopathies, post-HSCT TMA remains poorly understood. We report an analysis of the complement alternative pathway, which has recently been linked to the pathogenesis of both the Shiga toxin mediated and the atypical forms of HUS, with a focus on genetic variations in the complement Factor H (CFH) gene cluster and CFH autoantibodies in six children with post-HSCT TMA. We identified a high prevalence of deletions in CFH-related genes 3 and 1 (delCFHR3-CFHR1) and CFH autoantibodies in these patients with HSCT-TMA. Conversely, CFH autoantibodies were not detected in 18 children undergoing HSCT who did not develop TMA. Our observations suggest that complement alternative pathway dysregulation may be involved in the pathogenesis of post-HSCT TMA. These findings shed light on a novel mechanism of endothelial injury in transplant-TMA and may therefore guide the development of targeted treatment interventions.