Faculty Bibliography

Background: Zonulin (ZON) increases gut permeability after exposure to gliadin in children with celiac disease. Plasma zonulin levels are increased in children with NS. Protease activated receptor-2, which mediates ZON effect in enterocytes, is present on podocytes. Thus, gluten-induced elevations in ZON may affect glomerular permeability and mediate proteinuria in children with NS. We conducted this study to assess the efficacy of a GFD in controlling disease in children with difficult-to-manage NS.
Method(s): This multicenter, open-label trial tested the efficacy of a GFD in children with steroid-responsive, difficult-to-manage NS. The Treatment Period was 6 months. A positive response was defined as >=50% reduction in relapse rate versus the prior 6 months or discontinuation of >=1 immunosuppressive medication. The following data were tabulated: age, gender, race/ethnicity, serum creatinine, proteinuria, histopathology if available, and treatment. Serum was collected prior to and at completion of the Treatment Period to assess the effect on the glomerular cytoskeleton in vitro. Data are provided as mean+/-SD.
Result(s): 14 children (8F:6M) were enrolled, age 7.8+/-4.6 yr, baseline serum creatinine 0.46+/-0.12 mg/dl, and Up/c 0.45+/-0.49 (mg:mg). There were 11 Whites, 1 Black and 3 other racial groups and 2 children were Hispanic/Latino. The underlying disease was MCD in 10 and FSGS in 4 cases. At the end of the Treatment Period, 4 participants had a positive response (2 reduced relapse rate and 2 reduced medication burden), 5 had no benefit (2 withdrew before 6 months), 3 patients are in the 6-month Treatment Period, and 1 child was lost to follow-up. One adolescent had no change in relapse rate but responded to corticosteroids more rapidly on the GFD. Baseline plasma zonulin concentration was 19.4+/-1.7 vs 13.4+/-0.9 pg/mL in non-responders (n=4) vs GFD responders (n=2), respectively, P=0.01.
Conclusion(s): Up to a third of patients with difficult-to-manage NS have a favorable response to implementation of a GFD. An elevated plasma zonulin level may predict a poor response to the maneuver. A trial of this dietary intervention may be warranted in children with frequently relapsing or steroid dependent NS to minimize the need for immunosuppressive agents

Background: There is growing evidence that sodium is stored in a non-osmotic form in the interstitial compartment of skin and muscle. In these sites, sodium may contribute to the development of EH by altering the immune system. These effects may be reflected in peripheral blood (PB). We tested PB of children with EH to examine the diversity of immunophenotypes, and to test whether disease treatment changed circulating cells. We deployed high parameter flow cytometry, which allowed detailed characterization of T-cell subsets.
Method(s): Eight pediatric patients with EH were enrolled. PB was collected at baseline for all patients, and after 4 and 16 weeks of anti-hypertensive treatment for 3 patients. We designed a 24-parameter flow cytometry panel to enumerate various T-cell subsets, including naive, memory, dividing, exhausted, regulatory, and suppressive cells. We analyzed data using t-sne, a dimension reduction algorithm that provides a broad overview of the landscape of T-cell immunophenotypes, and applied bivariate difference gating to identify the cell populations uniquely altered with treatment.
Result(s): At baseline, 7 of 8 patients showed the expected diversity in T-cells subsets. There were dominant populations that differed by patient, suggesting heterogeneity that might be linked to clinical outcome. The 8th patient had a striking polarization in T-cell phenotype at baseline, with two major subpopulations and very few other cells. Her "skewed" T-cell landscape resolved with treatment, and we could precisely identify the cells lost. Cells were uniformly CD4+CD45RA+CD127+CD25-CD38+CCR4-Ki67-LAG3+CTLA4-CD39-IDO-HELIOS-FoxP 3-CXCR3-GITR+. This phenotype represents a class of naive, non-classical regulatory (i.e., suppressive) T-cells. Subsets also expressed other suppressive markers like LAP, GARP, and CD73. Interestingly, the other two patients also showed loss of cells expressing LAG3, CD73, LAP, and/or GARP with treatment.
Conclusion(s): Children with EH have heterogeneous regulatory T-cell subsets. Successful control of blood pressure with anti-hypertensive drugs re-shapes the T-cell landscape in PB, reducing the number of suppressive T-cells. Our approach-to precisely identify specific cell types altered with disease-is well-suited to identifying biomarkers, and can provide detailed mechanistic information that informs treatment approaches

Hypokalemia of renal origin can arise from genetic abnormalities in a variety of transporters or channel proteins that mediate tubular handling of potassium. Recently, mutations in claudin 10 have been documented in patients with hypokalemia in association with a range of other electrolyte abnormalities and skin and sweat gland manifestations. We report a 12-year-old Hispanic boy who presented with anhydrosis, aptyalism, alacrima, hypokalemia, and hypocalciuria, in whom we detected a homozygous mutation in the claudin 10 gene. During the 4-year follow-up period, he developed hypermagnesemia and a decline in estimated glomerular filtration rate to 59mL/min/1.73m². His unaffected parents and siblings were heterozygous for the mutation. We summarize the clinical phenotype encountered in patients with claudin 10 mutations. It is characterized by significant heterogeneity in electrolyte and extrarenal abnormalities and is associated with a risk for progressive loss of kidney function in up to 33% of cases. Awareness of this association between claudin 10 mutations and electrolyte abnormalities, namely hypokalemia and hypermagnesemia, sheds new light on the physiology of potassium and magnesium handling along the nephron and increases the likelihood of identifying the underlying tubular mechanism in patients with newly diagnosed hypokalemia with or without concomitant hypermagnesemia.

Background: Chronic illness in children has adverse effects on family members besides the patient and can impact the integrity and function of the family unit. Most previous studies have examined a single disease entity. However, there has been limited assessment comparing the effect of different illnesses on family function.
Method(s): Established patients treated in the pediatric ambulatory Nephrology or DM clinics were included in the study. Their parents were asked to complete the 2-page Pediatric Quality-of-Life Family Impact Module (PedsQL-FIM), version 2.0, a validated survey instrument. Clinical and laboratory data were retrieved from the electronic health record. Data were summarized as mean+/-SD. Disease group and child age were entered as predictors in linear regression analyses with FIM total and subscale scores as outcome variables. Comparisons between groups were assessed using paired t-tests.
Result(s): 96 patients (43 F: 53 M) were evaluated in the Nephrology Clinic and 55 (30 F: 25 M) in the DM Clinic. The mean age of the patients was 13.0+/-3.9 and 10.4+/- 6.3 yr, respectively. Within the KD sample, older age was significantly associated with lower scores on all FIM subscale scores. Gender was not a significant predicator for FIM scores in either disease group. Controlling for age, chronic illness group was a significant predictor of the FIM total and subscale scores. Parents of D patients endorsed significantly lower total FIM scores compared to the KD patients (D 58+/-16; KD 79+/-17 p <0.001) as well as on subscales of physical, emotional, social, and cognitive functioning, communication, worry, daily activities, family relationships, and reports of health-related quality of life (P<0.01).
Conclusion(s): Our findings confirm that chronic illness in childhood adversely affects a wide range of aspects of family function. The impact is greater in older children with KD and varies depending on the disease context. Families with children who have DM manifested greater disturbances than those with children who have isolated KD. Further study is warranted to assess the effects of the underlying renal disease and intensity of medical care and whether there are specific features can be used to identify vulnerable families

Interstitial nephritis (IN) is a relatively rare entity in children and adolescents that can be caused by a range of disorders including infection, medications, inflammatory bowel disease, and sarcoid. There is no proven therapy for this condition. We present 2 cases of biopsy-proven interstitial nephritis, of which 1 case was with granulomatous features that presented with unusual sonographic findings of discrete mass lesions in the kidney parenchyma bilaterally. Although a precise cause could not be identified in either case, 1 patient progressed to end-stage kidney disease (ESKD) and the other is in the early stages of treatment. We suggest that recognition of the atypical imaging features of interstitial nephritis may enable early recognition of this condition and avoid confusion with neoplastic or infectious processes.

Background: Angiogenesis inhibitors have an emerging role in the treatment of pediatric cancers. CNS tumors have high concentrations of pro-angiogenic factors and neo-vascularization. Much of what is known about angiogenesis inhibitors comes from adult studies, where they have been more widely used. Hypertension is a common side effect of this new drug class in adults. Limited information is available about the safety of these medications in children.
Method(s): A single center, retrospective chart review was conducted. Twenty-eight patients under 25 years of age with CNS tumors, who were followed by the Division of Pediatric Hematology and Oncology at NYU Medical Center, were identified who had received angiogenesis inhibitors developed hypertension. Chart review was conducted in 12 cases. The other cases met exclusion criteria or access to full EMR was unavailable.
Result(s): Seven (56%) patients developed hypertension within 9 months of initiation of the drugs, with most occurring in the first 3 months. Four were treated with bevacizumab, 2 axitinib, and 1 pazopanib. While one patient's symptoms resolved, the remaining 6 children required treatment with anti-hypertensive agents. Only two patients were referred to pediatric nephrology and were treated with amlodipine. The remaining patients were all given diuretics by the oncology team, with 3 requiring use of a second antihypertensive agent (ACE inhibitors).
Conclusion(s): Our findings are consistent with the adult literature and indicate that secondary hypertension is a frequent complication of angiogenesis inhibitor therapy. Poorly controlled hypertension in children has the potential to track into adulthood and is a major risk factor for cardiovascular morbidity and mortality. Identification and treatment of pediatric hypertension is an important health focus for pediatric oncology patients. Timely referral to a pediatric nephrologist should be coinsidered for treatment of angiogenesis inhibitor-associated hypertension

OBJECTIVES: Renal manifestations are the second most significant cause of morbidity and mortality in patients with tuberous sclerosis complex (TSC), and include renal cysts, angiomyolipomas, fat-poor lesions, and malignant tumors. These lesions begin in childhood and often lead to chronic kidney disease (CKD). Little is known on the incidence of early modifiable risk factors of CKD, such as proteinuria and hypertension, or subtle decreases in glomerular filtration rate that correspond to the early stages of CKD in children with TSC. The impact of genotype on these early manifestations of CKD has not been investigated. DESIGN: Retrospective chart review of 84 children and young adults with TSC. MEASUREMENTS: This study assessed the prevalence of hypertension, renal impairment, and proteinuria, as well as the genotype-phenotype correlations. RESULTS: Children and young adults with TSC2 mutations had a significantly higher rate of renal lesions, hypertension (36% vs 14%), and decreased renal function than those with TSC1 mutations. CONCLUSION: On the basis of estimated glomerular filtration rate and blood pressure, our findings are consistent with the hypothesis that TSC2 mutations are associated with more severe early renal involvement in children. There is a compelling need for close collaboration of nephrologists and neurologists to provide care to pediatric patients with TSC to improve screening and management of early manifestations of renal disease.

Renal tubule epithelial cells are high-energy demanding polarized epithelial cells. Liver kinase B1 (LKB1) is a key regulator of polarity, proliferation, and cell metabolism in epithelial cells, but the function of LKB1 in the kidney is unclear. Our unbiased gene expression studies of human control and CKD kidney samples identified lower expression of LKB1 and regulatory proteins in CKD. Mice with distal tubule epithelial-specific Lkb1 deletion (Ksp-Cre/Lkb1flox/flox) exhibited progressive kidney disease characterized by flattened dedifferentiated tubule epithelial cells, interstitial matrix accumulation, and dilated cystic-appearing tubules. Expression of epithelial polarity markers beta-catenin and E-cadherin was not altered even at later stages. However, expression levels of key regulators of metabolism, AMP-activated protein kinase (Ampk), peroxisome proliferative activated receptor gamma coactivator 1-alpha (Ppargc1a), and Ppara, were significantly lower than those in controls and correlated with fibrosis development. Loss of Lkb1 in cultured epithelial cells resulted in energy depletion, apoptosis, less fatty acid oxidation and glycolysis, and a profibrotic phenotype. Treatment of Lkb1-deficient cells with an AMP-activated protein kinase (AMPK) agonist (A769662) or a peroxisome proliferative activated receptor alpha agonist (fenofibrate) restored the fatty oxidation defect and reduced apoptosis. In conclusion, we show that loss of LKB1 in renal tubular epithelial cells has an important role in kidney disease development by influencing intracellular metabolism.

BACKGROUND Recent progress in the identification of Magnesium (Mg) transporters and channels has advanced our understanding of Mg homeostasis. The TRPM6 gene, which encodes an ion channel, contributes to the understanding transepithelial Mg transport. An association was identified between hypomagnesemia with secondary hypocalcemia and the TRPM6 gene. Recently a missense mutation in TRPM6 gene was reported (1). Several othergenes have also been reported in hereditary renal Mg loss. No definite phenotype-genotype correlation has been established. Paracellular transport of magnesium was clarified by the claudin 16-19 mutations. Claudins are tight junctions proteins located in the kidney; mutations in these key proteins are responsible for the condition called familial hypomagnesemia with hypercalciuria and nephrocalcinosis (2). Hypomagnesemia occurs in malabsorption, vitamin D deficiency and hypoparathyroidism. The syndrome of hypomagnesemia with secondary hypocalcemia is a rare disorder characterized by a defect in renal or intestinal Mg absorption, which can result in brain damage if not recognized early. We report a newborn who presented with convulsions, profound hypomagnesemia with hypocalcemia. CASE REPORT A full term male, born to Yemenite parents with no parental consanguinity nor any significant family history, presented at 12 days of life with new onset generalized convulsions. Initial studies showed: Mg <0.6 mg/dL (1.6-2.3 mg/dL), calcium 6.4mg/dl (8.3-10.3 mg/dL), phosphorus 10.3 mg/dl (2.7-4.5 mg/dL), glucose 81mg/dl. Genetic investigation is in progress. The baby was initially treated with anticonvulsants and calcium gluconate. Despite this treatment, seizures persisted. IV Mg boluses (50mg/kg)and Ca (100mg/kg) were then administered. Within 24 hrs serum Ca normalized, but Mg remained below normal. The baby was transitioned to PO Mg and Ca supplements. Serum 25 hydroxy vitamin D was <13ng/mL ergocalciferol 2000 unitswere supplemented. Fractional Mg excretion (FEMg) was elevated at 15% (1-8%) with a low serum Mg 1 mg/dL suggestive of renal loss of Mg. Renal ultrasound was normal. After 24 hrs of IV Ca and Mg, the seizures ceased. However, Mg levels remained suboptimal (highest 1.5mg/dl) despite high PO doses of Mg. The baby was discharged on high doses of Mg (100 mg q 6 hrs), Ca and Vit D supplementation. During follow up calcium and vitamin D were tapered then stopped. Supplemental Mg was increased to200mg q 6hrs to maintain Mg levels at least >1.0 mg/dl. CONCLUSION Primary hypomagnesemia can occur with other electrolyte abnormalities and may be life threatening. The diagnosis can be a challenge, and a high index of suspicion is needed. An inherited disorder should be suspected, and genetic studies are recommended. Despite high doses of Mg levels may remain subnormal. Early diagnosis and appropriate treatment are important to avoid irreversible neurologic damage