Avram Z. Traum

Urine proteomic profiling of pediatric nephrotic syndrome

The prognosis of pediatric nephrotic syndrome (NS) correlates with the responsiveness to glucocorticoid therapy. Steroid-resistant NS (SRNS) patients progress to end-stage renal disease, while steroid-sensitive NS (SSNS) and steroid-dependent (SDNS) patients do not. We have performed proteomic profiling of urine samples from a cross section of pediatric and adolescent subjects with SSNS, SRNS, and orthostatic proteinuria (OP) to identify urinary biomarkers of steroid resistance. We performed surface-enhanced laser desorption/ionization time of flight mass spectrometry (SELDI-TOF MS) on urine from 19 subjects with SSNS/SDNS in remission, 14 with SSNS/SDNS in relapse, 5 with SRNS in relapse, and 6 with OP. Genetic algorithm search of principal component space revealed a group of five peaks distinguishing SRNS subjects, with mass/charge (m/z) values of 3,917.07, 4,155.53, 6,329.68, 7,036.96, and 11,117.4. Our analyses identified the peak at m/z 11,117.4 with an accuracy of 95% for classifying SRNS. Multidimensional protein fractionation and mass spectrometric analysis of SRNS urine samples combined with immunodepletion identified the 11,117.4 protein as β2-microglobulin (B2M). Using an unbiased protein profiling approach, we have validated previously reported findings of B2M as a biomarker associated with SRNS. Prospective studies are warranted to establish additional biomarkers that would be predictive of SRNS.

Sensenbrenner syndrome (Cranioectodermal dysplasia): Clinical and molecular analyses of 39 patients including two new patients

Sensenbrenner syndrome, also known as cranioectodermal dysplasia, is a rare multiple anomaly syndrome with distinctive craniofacial appearance, skeletal, ectodermal, connective tissue, renal, and liver anomalies. Dramatic advances with next‐generation sequencing have expanded its phenotypic variability and molecular heterogeneity. We review 39 patients including two new patients, one with compound heterozygous novel mutations in WDR35 and a previously unreported multisutural craniosynostosis that may be a part of Sensenbrenner syndrome. In 14 of 25 (56.0%) patients pathogenic mutations have been identified in 4 different genes that regulate (intraflagellar) cilia transport. We compared Sensenbrenner syndrome to asphyxiating thoracic dystrophy‐Jeune syndrome (ATD‐JS) and other ciliopathies. Our analyses showed that the high anterior hairline, forehead bossing and dolichocephaly (accompanied by sagittal craniosynostosis in more than half of the patients) occur in almost all patients with Sensenbrenner syndrome. Metaphyseal dysplasia with narrow thorax, proximal limb shortness, and short fingers are typical of Sensenbrenner syndrome and ATD‐JS. Respiratory complications have been reported in both syndromes, usually less severe with Sensenbrenner syndrome. Proposed diagnostic criteria for Sensenbrenner syndrome include the distinctive craniofacial appearance, ubiquitous brachydactyly and ectodermal anomalies, and sagittal craniosynostosis. Mild heart defects have been noted, but there have been no atrioventricular canal or heterotaxy defects that are common in Ellis‐Van Creveld syndrome. We anticipate that the steady identification of molecularly defined patients may allow correlation of phenotype and genotype. Additional natural history data will improve genetic counseling and current guidelines.

Central nervous system lymphoproliferative disorder in pediatric kidney transplant recipients

Abstract:  Post‐transplant lymphoproliferative disorder (PTLD) is a complication of transplantation resulting from impaired immune surveillance because of pharmacologic immunosuppression. We present two cases of central nervous system (CNS) PTLD in children on calcineurin‐inhibitor free immunosuppression with dramatically different presentations and outcomes. One patient had brain and spinal cord lymphoma with a rapid and fatal course. The other patient had brain and ocular PTLD that responded to multimodal therapy with reduction of immunosuppression, high‐dose steroids, and rituximab given in a dose‐escalation protocol. This protocol may have enhanced the penetration of rituximab into the CNS. We review the literature on CNS and ocular PTLD and elaborate on the treatments available for both diseases.

Myocardial Tissue Remodeling in Adolescent Obesity

Background Childhood obesity is a significant risk factor for cardiovascular disease in adulthood. Although ventricular remodeling has been reported in obese youth, early tissue‐level markers within the myocardium that precede organ‐level alterations have not been described. Methods and Results We studied 21 obese adolescents (mean age, 17.7±2.6 years; mean body mass index [BMI], 41.9±9.5 kg/m2, including 11 patients with type 2 diabetes [T2D]) and 12 healthy volunteers (age, 15.1±4.5 years; BMI, 20.1±3.5 kg/m2) using biomarkers of cardiometabolic risk and cardiac magnetic resonance imaging (CMR) to phenotype cardiac structure, function, and interstitial matrix remodeling by standard techniques. Although left ventricular ejection fraction and left atrial volumes were similar in healthy volunteers and obese patients (and within normal body size‐adjusted limits), interstitial matrix expansion by CMR extracellular volume fraction (ECV) was significantly different between healthy volunteers (median, 0.264; interquartile range [IQR], 0.253 to 0.271), obese adolescents without T2D (median, 0.328; IQR, 0.278 to 0.345), and obese adolescents with T2D (median, 0.376; IQR, 0.336 to 0.407; P=0.0001). ECV was associated with BMI for the entire population (r=0.58, P<0.001) and with high‐sensitivity C‐reactive protein (r=0.47, P<0.05), serum triglycerides (r=0.51, P<0.05), and hemoglobin A1c (r=0.76, P<0.0001) in the obese stratum. Conclusions Obese adolescents (particularly those with T2D) have subclinical alterations in myocardial tissue architecture associated with inflammation and insulin resistance. These alterations precede significant left ventricular hypertrophy or decreased cardiac function.

Outcome of management strategies for BK virus replication in pediatric renal transplant recipients

Abstract:  Management of BKV infection is not well defined. Eighteen pediatric renal transplant patients with BKV‐PCR (+) were divided into three groups; Group 1: Viruria only (6), Group 2: Viremia with stable GFR (4), Group 3: Viremia with >25% decline in GFR and BKVAN on biopsy (8). With initial BKV‐PCR(+), Group 1 received no treatment; Group 2 had MMF reduced 30%; Group 3: 6/8 had CNI discontinuation, 2/8 had reduced MMF and cidofovir. BKV, GFR and histology were compared pre‐ and post‐treatment. In Group 1 viruria decreased in all patients; GFR remained stable. Group 2 showed reduced viremia with no GFR change. Group 3 showed reduced viremia in 8/8 patients. Patients with >50% decline in GFR from baseline (6/8) showed worse histology: 2/6 lost grafts despite no BKV on follow‐up biopsy. Our results show that with viruria alone no treatment is necessary; with viremia and stable GFR, reduced immunosuppression decreases viremia and maintains GFR. With viremia and reduced GFR, immunosuppression reduction with or without cidofovir decreases viremia and stabilizes GFR in most patients. Greater than 50% reduction in GFR at BKVAN diagnosis correlates with risk for graft loss. Serial monitoring of BKV viremia with early intervention may prevent BKVAN graft loss in children.

The need for tolerance in pediatric organ transplantation.

Transplantation is the preferred therapy for pediatric end stage diseases of a variety of solid organs. Unfortunately, however, transplantation does not restore patients to a normal life, because they are left on lifelong immunosuppression with its associated complications. In addition, even when immunosuppression is properly administered, there is progressive loss of allograft function through a process called “chronic allograft dysfunction” that leads to loss of ∼4% of transplanted organs per year. Exciting new findings in adult transplant patients now offer the hope that both the need for chronic immunosuppression and the loss of organs to chronic rejection may be avoided by the induction of transplantation tolerance—the specific elimination of the rejection response through modification of the immune system. Below, we will outline the history of immunosuppression and its problems and provide some insights into how we believe that the induction of tolerance will be of special benefit to children.

Granulomatous Interstitial Nephritis as a Manifestation of Crohn Disease

Granulomatous interstitial nephritis is a rare extraintestinal manifestation of Crohn disease that has been described previously in 4 patients. We report a 23-year-old man with a history of Crohn disease since age 6 years who was admitted to the hospital for weight loss, fever, and bloody diarrhea in the midst of a recent flare up during the past 2 months. Investigations revealed anemia, high erythrocyte sedimentation rate, high C-reactive protein level, and an elevated serum creatinine level. Histopathologic examination of tissue specimens obtained at renal biopsy demonstrated granulomatous interstitial nephritis. Crohn disease needs to be in the differential diagnosis of granulomatous interstitial nephritis and can be a manifestation of drug allergy or the Crohn disease itself.

Whole exome sequencing frequently detects a monogenic cause in early onset nephrolithiasis and nephrocalcinosis

The incidence of nephrolithiasis continues to rise. Previously, we showed that a monogenic cause could be detected in 11.4% of individuals with adult-onset nephrolithiasis or nephrocalcinosis and in 16.7-20.8% of individuals with onset before 18 years of age, using gene panel sequencing of 30 genes known to cause nephrolithiasis/nephrocalcinosis. To overcome the limitations of panel sequencing, we utilized whole exome sequencing in 51 families, who presented before age 25 years with at least one renal stone or with a renal ultrasound finding of nephrocalcinosis to identify the underlying molecular genetic cause of disease. In 15 of 51 families, we detected a monogenic causative mutation by whole exome sequencing. A mutation in seven recessive genes (AGXT, ATP6V1B1, CLDN16, CLDN19, GRHPR, SLC3A1, SLC12A1), in one dominant gene (SLC9A3R1), and in one gene (SLC34A1) with both recessive and dominant inheritance was detected. Seven of the 19 different mutations were not previously described as disease-causing. In one family, a causative mutation in one of 117 genes that may represent phenocopies of nephrolithiasis-causing genes was detected. In nine of 15 families, the genetic diagnosis may have specific implications for stone management and prevention. Several factors that correlated with the higher detection rate in our cohort were younger age at onset of nephrolithiasis/nephrocalcinosis, presence of multiple affected members in a family, and presence of consanguinity. Thus, we established whole exome sequencing as an efficient approach toward a molecular genetic diagnosis in individuals with nephrolithiasis/nephrocalcinosis who manifest before age 25 years.

Whole Exome Sequencing of Patients with Steroid-Resistant Nephrotic Syndrome

BACKGROUND AND OBJECTIVES Steroid-resistant nephrotic syndrome overwhelmingly progresses to ESRD. More than 30 monogenic genes have been identified to cause steroid-resistant nephrotic syndrome. We previously detected causative mutations using targeted panel sequencing in 30% of patients with steroid-resistant nephrotic syndrome. Panel sequencing has a number of limitations when compared with whole exome sequencing. We employed whole exome sequencing to detect monogenic causes of steroid-resistant nephrotic syndrome in an international cohort of 300 families. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS Three hundred thirty-five individuals with steroid-resistant nephrotic syndrome from 300 families were recruited from April of 1998 to June of 2016. Age of onset was restricted to <25 years of age. Exome data were evaluated for 33 known monogenic steroid-resistant nephrotic syndrome genes. RESULTS In 74 of 300 families (25%), we identified a causative mutation in one of 20 genes known to cause steroid-resistant nephrotic syndrome. In 11 families (3.7%), we detected a mutation in a gene that causes a phenocopy of steroid-resistant nephrotic syndrome. This is consistent with our previously published identification of mutations using a panel approach. We detected a causative mutation in a known steroid-resistant nephrotic syndrome gene in 38% of consanguineous families and in 13% of nonconsanguineous families, and 48% of children with congenital nephrotic syndrome. A total of 68 different mutations were detected in 20 of 33 steroid-resistant nephrotic syndrome genes. Fifteen of these mutations were novel. NPHS1, PLCE1, NPHS2, and SMARCAL1 were the most common genes in which we detected a mutation. In another 28% of families, we detected mutations in one or more candidate genes for steroid-resistant nephrotic syndrome. CONCLUSIONS Whole exome sequencing is a sensitive approach toward diagnosis of monogenic causes of steroid-resistant nephrotic syndrome. A molecular genetic diagnosis of steroid-resistant nephrotic syndrome may have important consequences for the management of treatment and kidney transplantation in steroid-resistant nephrotic syndrome.

The potential for tolerance in pediatric renal transplantation.

Purpose of reviewImmune tolerance has remained the Holy Grail in transplantation since the first kidney transplantation was performed over 50 years ago. Children present unique challenges in renal transplantation because of increased infectious risks and adolescent nonadherence to the intensive medication regimen necessary for allograft function. The current review presents recent studies and approaches toward achieving tolerance in renal transplantation and the prospects for pediatric patients. Recent findingsA number of approaches have been used toward minimization of immunosuppression in pediatric patients, but none has yet achieved true operational tolerance with maintenance of allograft function of all immunosuppression. Recent work in adult renal transplant recipients using combined kidney–bone marrow transplantation by the induction of transient mixed chimerism has allowed for full withdrawal of immunosuppression with stable long-term renal function. SummaryOn the basis of recent adult studies, the prospect of immune tolerance in pediatric renal transplantation remains hopeful and may be ready for extension to the adolescent population.