Assessing Utility of 24-Hour Ambulatory Blood Pressure Monitoring to Distinguish Pediatric Populations Presenting with Elevated Blood Pressure in Rhode Island.

This retrospective study aimed to assess the value of 24-hour ambulatory blood pressure monitoring (ABPM) in distinguishing primary from secondary hypertension in pediatric patients. Our study was conducted on 293 patients referred to a pediatric nephrology clinic over 11 years. Various ABPM parameters were analyzed, including daytime and nighttime systolic and diastolic blood pressures, heart rate, and blood pressure load. Among the participants, 74% were normotensive (white-coat hypertension), 21.5% had primary hypertension, and 4.4% had secondary hypertension. There were no significant differences in the analyzed variables between primary and secondary hypertension groups. Our findings suggest that ABPM might not reliably differentiate between the two in this cohort. As white-coat hypertension becomes more prevalent, ABPM remains a valuable tool in preventing unnecessary workups in children without sustained hypertension. However, our study did not identify specific endpoints for distinguishing primary from secondary hypertension.

Isolated benign persistent proteinuria with novel association of CUBN (cubilin) variants.

We present two siblings with persistent proteinuria and normal kidney function, each carrying the same compound heterozygous variants in the CUBN gene. The CUBN-related phenotype appears to be dependent upon both variant type and the domain site within the gene. Knowledge of CUBN status may allow for avoidance of invasive testing.

Pediatric Mineral and Bone Disorder of Chronic Kidney Disease and Cardiovascular Disease.

Chronic kidney disease is common and causes significant morbidity including shortened lifespans and decrease in quality of life for patients. The major cause of mortality in chronic kidney disease is cardiovascular disease. Cardiovascular disease within the chronic kidney disease population is closely tied with disordered calcium and phosphorus metabolism and driven in part by renal bone disease. The complex nature of renal, bone, and cardiovascular diseases was renamed as mineral and bone disorder of chronic kidney disease to encompass how bone disease drives vascular calcification and contributes to the development of long-term cardiovascular disease, and recent data suggest that managing bone disease well can augment and improve cardiovascular disease status. Pediatric nephrologists have additional obstacles in optimal mineral and bone disorder of chronic kidney disease management such as linear growth and skeletal maturation. In this article, we will discuss cardiovascular and bone diseases in chronic kidney disease and end-stage kidney disease patients with a focus on pediatric issues and concerns.

Mutation of complement factor B causing massive fluid-phase dysregulation of the alternative complement pathway can result in atypical hemolytic uremic syndrome.

Atypical hemolytic uremic syndrome is an ultra-rare disease characterized by microangiopathic hemolytic anemia, thrombocytopenia and acute kidney injury. Its pathogenesis is driven most frequently by dysregulated cell-surface control of the alternative pathway of complement secondary to inherited and/or acquired factors. Here we evaluated two unrelated patients with atypical hemolytic uremic syndrome. The first, a five-year-old Caucasian female, presented at 10 months with schistocytes, thrombocytopenia and kidney injury. The second, a 55-year-old Caucasian female, presented at age 31 following caesarean section for preeclampsia. Complement biomarker testing was remarkable for undetectable levels of C3 in both. Circulating levels of C5 and properdin were also low consistent with over-activity of the alternative and terminal pathways of complement. Genetic testing identified a heterozygous novel variant in CFB (c.1101 C>A, p.Ser367Arg) in both patients. Functional studies found strong fluid-phase C3 cleavage when normal and proband sera were mixed. Cell-surface C3b deposition was strongly positive when patient serum was supplemented with C3. In vitro control of C3 convertase activity could be restored with increased concentrations of factor H. Thus, CFB p.Ser367Arg is a gain-of-function pathogenic variant that leads to dysregulation of the alternative pathway in the fluid-phase and increased C3b deposition on cell surfaces. Our study highlights the complexities of complement-mediated diseases like atypical hemolytic uremic syndrome and illustrates the importance of functional studies at the variant level to gain insight into the disease phenotype.

Nephrolithiasis: A complication of pediatric diabetic ketoacidosis.

OBJECTIVE: To determine the frequency of nephrolithiasis as a complication of diabetic ketoacidosis (DKA) in pediatrics. METHODS: We performed a retrospective chart review of patients with DKA admitted to a pediatric hospital between January 2009 and July 2016. We identified patients with nephrolithiasis during admission for DKA. RESULTS: We identified 395 episodes of DKA over 7.5 years. Nephrolithiasis developed as a complication of DKA in 3 of those admissions (0.8%). All three patients with nephrolithiasis were males with new onset type 1 diabetes, aged 11 to 16.5 years. They all developed symptoms of nephrolithiasis after transition to subcutaneous insulin. One patient had subsequent worsening acidosis that required an additional 24 hours of IV insulin administration. CONCLUSIONS: Nephrolithiasis is a rare complication of pediatric DKA, and should be considered in children with DKA who develop hematuria, flank pain, or suprapubic pain. Nephrolithiasis can increase insulin resistance due to increased pain and inflammation, so these patients should be monitored closely for recurrence of DKA. As patients with diabetes have increased risk of chronic kidney disease and nephrolithiasis can cause kidney injury, risk factors for nephrolithiasis should be identified and addressed to avoid subsequent kidney damage.

Two cases of humoral hypercalcemia of malignancy complicating infantile fibrosarcoma.

We report two infants with infantile fibrosarcoma (IFS) complicated by severe hypercalcemia. Assessment demonstrated suppressed parathyroid hormone and 1,25-dihydroxyvitamin D levels with elevated circulating levels of parathyroid hormone related protein, indicating the diagnosis of humoral hypercalcemia of malignancy (HHM). HHM is a paraneoplastic syndrome rarely associated with pediatric malignancies. Hypercalcemia manifested clinically with neurologic symptoms and soft tissue calcium deposition and required aggressive management with intravenous fluids, diuretics, and supplemental electrolytes. Following treatment with neoadjuvant chemotherapy, serum calcium levels precipitously declined requiring calcium repletion. These cases highlight the improvement of hypercalcemia secondary to HHM following chemotherapy.

Estimated GFR and circulating 24,25-dihydroxyvitamin D3 concentration: a participant-level analysis of 5 cohort studies and clinical trials.

BACKGROUND: Decreased glomerular filtration rate (GFR) leads to reduced production of 1,25-dihydroxyvitamin D3 from 25-hydroxyvitamin D3 (25[OH]D3). Effects of low GFR on vitamin D catabolism are less well understood. We tested associations of estimated GFR (eGFR) with the circulating concentration of 24,25-dihydroxyvitamin D3 (24,25[OH]2D3), the most abundant product of 25(OH)D3 catabolism, across populations with a wide range of GFRs. STUDY DESIGN: Cross-sectional study. SETTING & PARTICIPANTS: 9,596 participants in 5 cohort studies and clinical trials: the Diabetes Control and Complications Trial (N=1,193), Multi-Ethnic Study of Atherosclerosis (N=6,470), Cardiovascular Health Study (N=932), Seattle Kidney Study (N=289), and Hemodialysis Study (N=712). PREDICTOR: eGFR. OUTCOME: Circulating 24,25(OH)2D3 concentration. MEASUREMENTS: GFR was estimated from serum creatinine using the Chronic Kidney Disease Epidemiology Collaboration equation. Vitamin D metabolites were measured by mass spectrometry. RESULTS: Circulating 24,25(OH)2D3 concentration was correlated with circulating 25(OH)D3 concentration (Pearson r range, 0.64-0.88). This correlation was weaker with lower eGFRs. Moreover, the increment in 24,25(OH)2D3 concentration associated with higher 25(OH)D3 concentration (slope) was lower with lower eGFRs: 2.06 (95% CI, 2.01-2.10), 1.77 (95% CI, 1.74-1.81), 1.55 (95% CI, 1.48-1.62), 1.17 (95% CI, 1.05-1.29), 0.92 (95% CI, 0.74-1.10), 0.61 (95% CI, 0.22-1.00), and 0.37 (95% CI, 0.35-0.39) ng/mL of 24,25(OH)2D3 per 10 ng/mL of 25(OH)D3 for eGFRs≥90, 60-89, 45-59, 30-44, 15-29, and <15 mL/min/1.73 m2 and end-stage renal disease treated with hemodialysis, respectively. As a result, at a 25(OH)D3 concentration of 20 ng/mL, mean 24,25(OH)2D3 concentrations were 2.92 (95% CI, 2.87-2.96), 2.68 (95% CI, 2.64-2.72), 2.35 (95% CI, 2.26-2.45), 1.92 (95% CI, 1.74-2.10), 1.69 (95% CI, 1.43-1.95), 1.14 (95% CI, 0.62-1.66), and 1.04 (95% CI,1.02-1.07) ng/mL for each category, respectively. This interaction was independent of other relevant clinical characteristics. Race, diabetes, urine albumin excretion, and circulating parathyroid hormone and fibroblast growth factor 23 concentrations more modestly modified the association of 24,25(OH)2D3 with 25(OH)D3. LIMITATIONS: Lack of direct pharmacokinetic measurements of vitamin D catabolism. CONCLUSIONS: Lower eGFR is associated strongly with reduced vitamin D catabolism, as measured by circulating 24,25(OH)2D3 concentration.

Effects of a high-protein diet on regulation of phosphorus homeostasis.

CONTEXT: High-protein diets, which are popular for weight loss, contain large quantities of phosphorus. Phosphorus excess and consequent changes in phosphorus regulatory hormones are implicated in vascular calcification and cardiovascular disease. OBJECTIVE: We tested the hypothesis that a moderate increase in dietary phosphorus during a high-protein diet leads to changes in phosphorus-responsive hormones. DESIGN, PARTICIPANTS, AND SETTING: We conducted a post hoc analysis of a sequential dietary modification trial in 19 healthy volunteers in the general community. INTERVENTION: Participants received 2 weeks of a weight-maintaining, low-protein (15%) diet, followed by 2 weeks of an isocaloric, high-protein (30%) diet, followed by 12 weeks of an ad libitum high-protein (30%) diet. MAIN OUTCOME MEASURES: Using previously collected samples, plasma concentrations of fibroblast growth factor-23 (FGF-23), PTH, 1,25-dihydroxyvitamin D, and 24,25-dihydroxyvitamin D were measured at 8 time points to assess 24-hour variability and in 24-hour pooled samples to delineate changes at the end of each diet period. RESULTS: Mean dietary phosphorus intake during each study period was 1556, 2071, and 1622 mg/d, respectively. Plasma concentrations of FGF-23 and vitamin D metabolites varied in a diurnal pattern; plasma PTH concentrations varied in a bimodal pattern. After changing from a low- to high-protein isocaloric diet, plasma FGF-23 concentrations decreased slightly (mean -4.48 pg/mL, 95% confidence interval 1.88-7.07). There were no other statistically significant changes in phosphorus regulatory hormones in response to diet modifications. CONCLUSIONS: Among healthy people, an approximate 33% increase in dietary phosphorus after institution of a high-protein diet does not cause large changes in measured concentrations of phosphorus regulatory hormones.