Spontaneous tendon or ligament ruptures in patients undergoing dialysis: First pediatric case report and literature review.

Spontaneous tendon or ligament ruptures are quite rare and mostly associated with chronic systemic diseases such as diabetes mellitus, systemic lupus erythematosus, rheumatoid arthritis, and chronic kidney disease (CKD). In this study, we present the first documented case of a spontaneous rupture of the medial patellofemoral ligament (MPFL) in a pediatric patient. The patient was undergoing long-term peritoneal dialysis (PD) and had a history of severe secondary hyperparathyroidism. Additionally, we discussed spontaneous tendon and ligament ruptures associated with CKD or dialysis through a comprehensive literature review. This case report highlights the importance of recognizing that spontaneous tendon or ligament injuries are not exclusive to adults; children with CKD can also be affected. Several factors including poor parathyroid hormone (PTH) and metabolic acidosis control, prolonged CKD duration and presence of malnutrition play role in the pathogenesis. Early diagnosis is crucial as it allows for timely surgical intervention and leads to a favorable functional recovery.

Variable phenotype and genotype of pediatric patients with HNF1B nephropathy.

AIMS: Hepatocyte nuclear factor 1ß (HNF1B) mutations are the most common monogenic cause of congenital anomalies of the kidney and urinary tract (CAKUT). We aimed to investigate clinical and genetic characteristics of patients with HNF1B nephropathy to expand its phenotypic and genetic spectrum. MATERIALS AND METHODS: This retrospective cohort study included 16 unrelated pediatric patients (6 females, 10 males) from 13 families with genetically confirmed HNF1B-related nephropathy. RESULTS: Abnormal prenatal kidney abnormalities were present in 13 patients (81.3%). The most common antenatal kidney abnormality was kidney cysts, which were observed in 8 patients (61.5%). Urinary system abnormalities (vesicoureteral reflux (VUR) and ureteropelvic junction obstruction (UPJO)) were present in 4 patients (25%). HNF1B analysis uncovered missense variants in 4 families (30.8%) as the most common genetic abnormality. In addition, 4 novel pathological variations have been defined. During follow-up, hypomagnesemia and hyperuricemia were observed in 7 (43.8%) and 5 patients (31.3%), respectively. None of the patients with a missense variant had hypomagnesemia. However, 7 out of 12 patients (58.3%) with a non-missense variant had hypomagnesemia (p = 0.09). None of the patients had an HNF1B score below 8, and the mean score was 15.3 ± 4.4. The mean follow-up period was 7.4 ± 5.0 years. While 100% of patients (n = 4) with missense variants were in various stages of CKD (CKD2: 2 patients, CKD3: 2 patients), 25% of those with non-missense variants had CKD (CKD2, 3, and 5; 1 patient, respectively) (p = 0.026). CONCLUSION: Patients with HNF1B-associated disease have concomitant urinary system abnormalities such as VUR or UPJO. Missense variants seem to be the most common pathological variations in HNF1B gene and have higher risk of CKD.

Adolescence-onset atypical hemolytic uremic syndrome: is it different from infant-onset?

BACKGROUND: Atypical hemolytic uremic syndrome (aHUS) is a rare, mostly complement-mediated thrombotic microangiopathy. The majority of patients are infants. In contrast to infantile-onset aHUS, the clinical and genetic characteristics of adolescence-onset aHUS have not been sufficiently addressed to date. METHODS: A total of 28 patients (21 girls, 7 boys) who were diagnosed as aHUS between the ages of ≥10 years and <18 years were included in this study. All available data in the Turkish Pediatric aHUS registry were collected and analyzed. RESULTS: The mean age at diagnosis was 12.8±2.3 years. Extra-renal involvement was noted in 13 patients (46.4%); neurological involvement was the most common (32%). A total of 21 patients (75%) required kidney replacement therapy. Five patients (17.8%) received only plasma therapy and 23 (82%) of the patients received eculizumab. Hematologic remission and renal remission were achieved in 25 (89.3%) and 17 (60.7%) of the patients, respectively. Compared with the infantile-onset aHUS patients, adolescent patients had a lower complete remission rate during the first episode (p = 0.002). Genetic analyses were performed in all and a genetic variant was detected in 39.3% of the patients. The mean follow-up duration was 4.9±2.6 years. At the last visit, adolescent patients had lower eGFR levels (p = 0.03) and higher rates of chronic kidney disease stage 5 when compared to infantile-onset aHUS patients (p = 0.04). CONCLUSIONS: Adolescence-onset aHUS is a rare disease but tends to cause more permanent renal dysfunction than infantile-onset aHUS. These results may modify the management approaches in these patients.

Allelic Variants of the Complement Genes in Acute Postinfectious Glomerulonephritis.

Acute postinfectious glomerulonephritis (APIGN) is one of the most common causes of acute glomerulonephritis in children. It may lead to inflammation and proliferation of glomerular tissue through immunologic mechanisms (Balasubramanian R, Paediatr Int Child Health 2017;37:240-247).

A rare cause of nephrotic syndrome-sphingosine-1-phosphate lyase (SGPL1) deficiency: 6 cases and a review of the literature.

BACKGROUND: Recently, recessive mutations in SGPL1 (sphingosine-1-phosphate lyase), which encodes the final enzyme of sphingolipid metabolism, have been reported to cause steroid-resistant nephrotic syndrome, adrenal insufficiency, and many other organ/system involvements. We aimed to determine the clinical and genetic characteristics, and outcomes in patients with SGPL1 mutations. METHODS: The study included 6 patients with bi-allelic SGPL1 mutation. Clinical, genetic, and laboratory characteristics, and outcomes of the patients were evaluated retrospectively. We also reviewed previously reported patients with SGPL1 mutations and compared them to the presented patients. RESULTS: The median age at kidney presentation was 5 months. Four patients (67%) were diagnosed before age 1 year. Kidney biopsy showed focal segmental glomerulosclerosis in 2 patients and diffuse mesangial sclerosis in one patient. Steroids were given to 3 patients, but they did not respond. All 6 patients progressed to chronic kidney disease; 5 required kidney replacement therapy (KRT) at a median age of 6 months. Deceased kidney transplantation was performed in one patient. All 6 patients had adrenal insufficiency, of which 5 were diagnosed at age < 6 months. Three patients had hypothyroidism, 2 had ichthyosis, 4 had immunodeficiency, 5 had neurological findings, and 2 had genitourinary system anomalies. Four patients died at a median age of 30.5 months. Two patients are being followed up with KRT. One patient had a novel mutation. CONCLUSIONS: Patients with SGPL1 mutations have a poor prognosis, and many types of extrarenal organ/system involvement beyond adrenal insufficiency can be seen. Genetic diagnosis of such patients is important for treatment, genetic counseling, and screening for comorbid conditions. A higher resolution version of the Graphical abstract is available as Supplementary information.

Electrocardiographic measurements in children with pre-dialysis chronic kidney disease and undergoing kidney replacement therapy.

Cardiovascular diseases are the main causes of morbidity in children with chronic kidney disease (CKD). Electrocardiography (ECG) can provide important information about cardiac functions and parameters associated with sudden cardiac death. This study aims to evaluate the potentially dangerous changes in CKD and kidney replacement therapies by ECG and to determine the value of ECG in predicting cardiovascular outcome compared with echocardiography. 101 patients with CKD were divided into subgroups according to treatment modalities as pre-dialysis CKD, hemodialysis (HD), peritoneal dialysis (PD) and kidney transplantation (KTx). Differences in anthropometric measurements, laboratory results, blood pressures, ECG monitoring were compared within groups as well as with 40 healthy controls. Available echocardiographic findings were noted. In the patients, HD group had highest frequency of hypertension. ECG revealed prolonged QTc as more frequent (16.8% vs 0%, p = 0.006) and higher QTcD (56.7 ± 6.5 vs 39.9 ± 5.1 ms, p = 0.001) in the patients compared to controls, especially in dialysis patients, whereas lowest values were in KTx subgroup. Left ventricular (LV) hypertrophy (LVH) was more frequent (47.1%) in HD compared to other CKD subgroups in ECG (p = 0.052). Echocardiography also showed LV mass index as highest in HD and lowest in KTx (121.4 ± 55.7 vs 63.7 ± 18.3 g/m2, p = 0.000), with numerically highest LVH in HD (58.3%, p = 0.063).  Conclusion: ECG can be used to detect cardiovascular problems in patients with CKD, especially in HD. As ECG results were in line with echocardiography, patients with ECG abnormalities suggestive of LVH should be referred for echocardiographic assessment. What is Known: • Cardiovascular diseases such as coronary artery disease, congestive heart failure, arrhythmias and sudden cardiac death are major causes of morbidity and mortality in chronic kidney disease. • Electrocardiography has significant advantages in demonstrating cardiac functions in children because it is readily available, non-invasive and often non-experts can interpret the results. What is New: • The heart rate is higher, QTc is longer and QTcD is higher in dialysis patients and the prolonged QTc is more frequent in patients with underlying glomerular diseases. • Left ventricular hypertrophy is more common in HD patients and those with hypertension, hypercalcemia, anemia or glomerular etiology. The cardiovascular risky conditions are less frequent in the patients with kidney transplantation.

Efficacy and safety of anti-interleukin-1 in children with colchicine-resistant familial Mediterranean fever.

BACKGROUND: The aim of this study was to evaluate the efficacy and safety of anti-interleukin-1 (IL-1) therapies in colchicine-resistant pediatric patients with familial Mediterranean fever (FMF). METHODS: In this study, we retrospectively evaluated 656 children with FMF and 27 patients who had been treated with anti-IL-1 therapies (anakinra/canakinumab) . Clinical and laboratory features, MEFV gene mutations, treatment responses were investigated. RESULTS: Twenty of the patients were treated with anakinra (the treatment of 6 patients who initially used anakinra was switched to canakinumab in the follow-up period), and 13 patients were treated with canakinumab. Clinical symptom and severity scores decreased in all patients A decrease in acute phase reactants was also observed in patients. A total of 18 (66%) patients had a M694V homozygous mutation, while 24 (89%) patients had a M694V mutation, at least in one allele. CONCLUSIONS: FMF patients with colchicine resistance may progress to amyloidosis. IL-1 antagonist treatment could be used safely with a favorable outcome in pediatric patients with FMF resistance to colchicine therapy and/or who have renal amyloidosis.

Does Age at Onset Affect the Clinical Presentation of Familial Mediterranean Fever in Children?

BACKGROUND/OBJECTIVE: The aim of this study was to compare the clinical and demographic features and evaluate the phenotypic and genotypic differences of pediatric familial Mediterranean fever (FMF) patients according to their age at disease onset. METHODS: Records of 854 patients who were diagnosed with FMF between 2006 and 2017 were evaluated. Patients were divided into 2 subgroups according to their age at disease onset. Group 1 comprised FMF patients who had experienced their first attack at 2 years or younger (younger onset), and group 2 comprised FMF patients who had experienced their first attack at older than 2 years. RESULTS: There were 155 patients in group 1 and 699 patients in group 2. Delay in diagnosis, attack frequency, duration of attacks, fever, chest pain, erysipelas-like erythema, incidence of family history, anti-interleukin 1 therapy use, and M694V homozygous and M680I homozygous mutations were significantly higher in group 1, whereas arthralgia and abdominal pain were significantly higher in group 2. There were no significant differences in arthritis, amyloidosis, and protracted febrile myalgia between the groups. The colchicine dose at last visit and Pras activity score were higher in group 1. CONCLUSIONS: It seems that FMF patients with a younger onset has a more severe disease course. They needed higher doses of colchicine to control the attacks. M694V and M680I homozygous mutations presented more frequently in younger-onset FMF patients. Increased awareness of physicians of the early presentation of FMF may prevent delays in FMF diagnosis.

Predictors of persistent inflammation in children with familial Mediterranean fever.

OBJECTIVES: Persistent inflammation is an insidious feature of familial Mediterranean fever (FMF) that may cause chronic complications. This study aimed to investigate the predictors of persistent inflammation in children with FMF. METHODS: The medical charts of 1077 paediatric FMF patients were retrospectively collected. The patients were divided into two groups: with and without subclinical inflammation. RESULTS: A total of 133 (12%) patients had persistent inflammation. M694V homozygosity, colchicine resistance, positive family history for FMF, erysipelas-like erythema, leg pain, arthritis, chest pain, inflammatory comorbidities, early disease onset, high PRAS score, and long attack duration were established as independent predictors of persistent inflammation (P < .001, P < .001, P < .001, P < .001, P = 0.006, P < .001, P < .001, P = .014, P < .001, P < .001, and P < .001, respectively). However, gender, abdominal pain, fever, and attack frequency were not found to be independent risk factors for predicting persistent inflammation (P = .412, P = .531, P = .451, and P = .693, respectively). CONCLUSIONS: M694V homozygosity, colchicine resistance, positive family history, erysipelas-like erythema, leg pain, arthritis, chest pain, inflammatory comorbidities, early disease onset, high activity score, and long attack duration may be predictors of persistent inflammation in FMF. These predictors may help clinicians suspect the occurrence of subclinical inflammation and should aid in better disease management in FMF.

Active vitamin D is cardioprotective in experimental uraemia but not in children with CKD Stages 3-5.

BACKGROUND: Uraemic cardiac remodelling is associated with vitamin D and Klotho deficiency, elevated fibroblast growth factor 23 (FGF23) and activation of the renin-angiotensin system (RAS). The cardioprotective properties of active vitamin D analogues in this setting are unclear. METHODS: In rats with 5/6 nephrectomy (5/6Nx) treated with calcitriol, the cardiac phenotype and local RAS activation were investigated compared with controls. A nested case-control study was performed within the Cardiovascular Comorbidity in Children with Chronic Kidney Disease (4C) study, including children with chronic kidney disease (CKD) Stages 3-5 [estimated glomerular filtration rate (eGFR) 25 mL/min/1.73 m2] treated with and without active vitamin D. Echocardiograms, plasma FGF23 and soluble Klotho (sKlotho) were assessed at baseline and after 9 months. RESULTS: In rats with 5/6Nx, left ventricular (LV) hypertrophy, LV fibrosis and upregulated cardiac RAS were dose-dependently attenuated by calcitriol. Calcitriol further stimulated FGF23 synthesis in bone but not in the heart, and normalized suppressed renal Klotho expression. In the 4C study cohort, treatment over a mean period of 9 months with active vitamin D was associated with increased FGF23 and phosphate and decreased sKlotho and eGFR compared with vitamin D naïve controls, whereas LV mass index did not differ between groups. CONCLUSIONS: Active vitamin D ameliorates cardiac remodelling and normalizes renal Klotho expression in 5/6Nx rats but does not improve the cardiac phenotype in children with CKD Stages 3-5. This discrepancy may be due to further enhancement of circulating FGF23 and faster progression of CKD associated with reduced sKlotho and higher serum phosphate in vitamin D-treated patients.

Transplantation in pediatric aHUS within the era of eculizumab therapy.

aHUS is caused by the over-activation and dysregulation of the alternative complement pathway. Data regarding outcomes of pediatric aHUS patients after kidney transplantation are still very scarce. Accordingly, the aim of this study was to describe the clinical findings and outcomes of pediatric aHUS patients after renal transplantation. This is a retrospective, multicenter study including 12 patients from the national registry system. Among the 12 patients, eight had received prophylactic eculizumab and none of those patients (except one) had experienced aHUS recurrence during a median follow-up period of 58.5 (min-max, 4-94) months. Although eculizumab had been started on the day before transplantation in one of them, aHUS recurrence occurred during the transplantation procedure. Eculizumab had been stopped in only one patient who had no complement gene mutation after 35 months of therapy, and recurrence had not been observed during the 19 months of follow-up. In three patients, maintenance doses had been spaced out without any recurrence. One additional patient with anti-CFH antibody received only two doses of eculizumab for transplantation and had been followed for 46 months without aHUS recurrence. The remaining three patients had not received anti-C5 therapy and none of those patients experienced aHUS recurrence during a median follow-up period of 21 (min-max, 9-42) months. Prophylactic eculizumab is a safe and effective treatment for the prevention of aHUS recurrence. Eculizumab interval prolongation, discontinuation, and transplantation without eculizumab prophylaxis can be tried in selected patients with close follow-up.

Erysipelas-like erythema in children with familial Mediterranean fever.

OBJECTIVES: Erysipelas-like erythema (ELE) is a well-known pathognomonic skin lesion associated with familial Mediterranean fever (FMF). The aim of this study was to describe the clinical and demographic features and phenotypic differences between paediatric FMF patients with and without ELE. METHODS: We retrospectively collected the medical charts of paediatric patients who had been diagnosed with FMF and followed by the Paediatric Rheumatology Department of Gazi University, Turkey, from 2006 to 2016. RESULTS: Among 782 FMF patients, 59 (33 males and 26 females; median age, 11.1±5.1) were found to have ELE. More patients had arthritis in the ELE group than in the other group (p=0.011). Arthritis occurred in the ankle (77.4%), knee (19.3%) and hip (3.2%) joints. The coexistence of arthritis and ELE was seen in 12 (20.3%) patients. All ELE plaques were located on the lower legs and dorsum of the feet. Eleven patients (18.6%) presented with ELE as the initial symptom and were diagnosed with FMF, and 48 (81.4%) patients experienced ELE attacks while receiving colchicine therapy. The median dose of colchicine at last visit, PRAS activity score and M694V homozygous mutation status were significantly higher in the ELE group than in the other group (p=0.041, p=0.001 and p=0.023, respectively). CONCLUSIONS: ELE is an uncommon but important feature of FMF. In patients with ELE, arthritis is more frequently encountered, and M694V homozygous mutation is more frequently found. FMF patients with ELE have more severe disease activity, and they use higher doses of colchicine in relation to this severe disease course.

COL4A3 mutation is an independent risk factor for poor prognosis in children with Alport syndrome.

BACKGROUND: Alport syndrome (AS) is an inherited glomerular disease caused by mutations in COL4A3, COL4A4, or COL4A5. Associations between clinical manifestations and genotype are not yet well defined. Our study aimed to define clinical and genetic characteristics, establish genotype-phenotype correlations, and determine prognosis of AS in children. METHODS: A total of 87 children with AS from 10 pediatric nephrology centers, whom had genetic analyses performed at the Hacettepe University Nephrogenetics Laboratory between February 2017 and February 2019, were included. Data regarding demographics, family history, clinical and laboratory characteristics, histopathological and genetic test results, treatments, and yearly follow-up results were retrospectively analyzed. RESULTS: Of 87 patients, 16% presented with nephrotic syndrome. In patients with nephrotic syndrome, kidney biopsy findings showed focal segmental glomerulosclerosis (FSGS) in 79%, and COL4A3 mutations were the leading genetic abnormality (50%). Twenty-four percent of all patients progressed to chronic kidney disease (CKD). The rate of progression to CKD and the decline in the glomerular filtration rate of the patients with COL4A3 mutation were higher than other mutation groups (p < 0.001 and p = 0.04, respectively). In kidney survival analysis, nephrotic syndrome presentation, histopathology of FSGS, COL4A3 mutations, and autosomal recessive inheritance were found as independent risk factors for earlier progression to CKD. Cyclosporin A treatment did not improve kidney survival. CONCLUSIONS: We emphasize that genetic testing is important for patients suspected as having AS. Furthermore, COL4A mutations should be considered in patients with FSGS and steroid-resistant nephrotic syndrome. This approach will shed light on the prognosis of patients and help with definitive diagnosis, preventing unnecessary and potentially harmful medications. Graphical abstract.

Renal Biopsy Prognostic Findings in Children With Atypical Hemolytic Uremic Syndrome.

BACKGROUND: The aim of this study was to investigate the histopathological findings in kidney biopsies in children with atypical hemolytic uremic syndrome (aHUS) and to determine whether specific pathological findings in aHUS have a prognostic value. METHODS: Renal biopsy specimens of 29 patients who were recorded in the national Turkish aHUS registry database were available for review. Histopathological findings were compared with the clinical and laboratory features at the presentation and the final outcome. RESULTS: The mean age at presentation and follow-up period was 4.9 ± 3.9 and 3.9 ± 3.0 years, respectively. The median time interval from the first symptom to biopsy was 10 days. Vascular thrombosis and interstitial fibrosis were significantly related to chronic kidney disease (CKD) requiring dialysis or kidney transplantation during follow-up (5.6-fold, for both). Glomerular necrosis, cortical necrosis, and glomerular sclerosis were markedly associated with CKD without dialysis (6.2-fold, 13.3-fold, and 8.8-fold, respectively). However, presence of endothelial swelling, subendothelial widening, and fragmented erythrocytes was found to be correlated with a favorable final outcome. CONCLUSIONS: Presence of vascular thrombosis, cortical necrosis, and glomerular sclerosis in histopathological evaluation correlated with developing CKD. Chronic changes in the interstitial compartment were also related to poor prognosis, a finding that has been shown for the first time in pediatric aHUS cases.

Indoxyl sulfate associates with cardiovascular phenotype in children with chronic kidney disease.

BACKGROUND: Cardiovascular disease is the leading cause of death in children with chronic kidney disease (CKD). Serum levels of gut-derived uremic toxins increase with deterioration of kidney function and are associated with cardiac comorbidities in adult CKD patients. METHODS: Indoxyl sulfate (IS) and p-cresyl sulfate (pCS) were measured by high-performance liquid chromatography in serum of children participating in the Cardiovascular Comorbidity in Children with CKD (4C) Study. Results were correlated with measurements of the carotid intima-media thickness (cIMT), central pulse wave velocity (PWV), and left ventricular mass index (LVMI) in children aged 6-17 years with initial eGFR of 10-60 ml/min per 1.73 m2. RESULTS: The median serum levels of total IS and of pCS, measured in 609 patients, were 5.3 µmol/l (8.7) and 17.0 µmol/l (21.6), respectively. In a multivariable regression model, IS and pCS showed significant positive associations with urea and negative associations with eGFR and uric acid. Furthermore, positive associations of pCS with age, serum albumin, and non-Mediterranean residency and a negative association with glomerular disease were observed. By multivariable regression analysis, only IS was significantly associated with a higher cIMT SDS at baseline and progression of PWV SDS within 12 months, independent of other risk factors. CONCLUSIONS: Serum levels of gut-derived uremic toxins IS and pCS correlated inversely with eGFR in children. Only IS was significantly associated with surrogate markers of cardiovascular disease in this large pediatric CKD cohort.

Correction to: Diagnostic utility of a targeted next-generation sequencing gene panel in the clinical suspicion of systemic autoinflammatory diseases: a multi-center study.

The second affiliation of the corresponding author Eda Tahir Turanli was incorrectly published as Istanbul Medeniyet University instead of Istanbul Technical University.

Diagnostic utility of a targeted next-generation sequencing gene panel in the clinical suspicion of systemic autoinflammatory diseases: a multi-center study.

Systemic autoinflammatory diseases (sAIDs) are a heterogeneous group of disorders, having monogenic inherited forms with overlapping clinical manifestations. More than half of patients do not carry any pathogenic variant in formerly associated disease genes. Here, we report a cross-sectional study on targeted Next-Generation Sequencing (NGS) screening in patients with suspected sAIDs to determine the diagnostic utility of genetic screening. Fifteen autoinflammation/immune-related genes (ADA2-CARD14-IL10RA-LPIN2-MEFV-MVK-NLRC4-NLRP12-NLRP3-NOD2-PLCG2-PSTPIP1-SLC29A3-TMEM173-TNFRSF1A) were used to screen 196 subjects from adult/pediatric clinics, each with an initial clinical suspicion of one or more sAID diagnosis with the exclusion of typical familial Mediterranean fever (FMF) patients. Following the genetic screening, 140 patients (71.4%) were clinically followed-up and re-evaluated. Fifty rare variants in 41 patients (20.9%) were classified as pathogenic or likely pathogenic and 32 of those variants were located on the MEFV gene. We detected pathogenic or likely pathogenic variants compatible with the final diagnoses and inheritance patterns in 14/140 (10%) of patients for the following sAIDs: familial Mediterranean fever (n = 7), deficiency of adenosine deaminase 2 (n = 2), mevalonate kinase deficiency (n = 2), Muckle-Wells syndrome (n = 1), Majeed syndrome (n = 1), and STING-associated vasculopathy with onset in infancy (n = 1). Targeted NGS panels have impact on diagnosing rare monogenic sAIDs for a group of patients. We suggest that MEFV gene screening should be first-tier genetic testing especially in regions with high carrier rates. Clinical utility of multi-gene testing in sAIDs was as low as expected, but extensive genome-wide familial analyses in combination with exome screening would enlighten additional genetic factors causing disease.

Effects of nutritional vitamin D supplementation on markers of bone and mineral metabolism in children with chronic kidney disease.

Background: We investigated the effects of nutritional vitamin D supplementation on markers of bone and mineral metabolism, i.e. serum levels of fibroblast growth factor 23 (FGF23), Klotho, bone alkaline phosphatase (BAP) and sclerostin, in two cohorts with chronic kidney disease (CKD). Methods: In all, 80 vitamin D-deficient children were selected: 40 with mild to moderate CKD from the ERGO study, a randomized trial of ergocalciferol supplementation [estimated glomerular filtration rate (eGFR) 55 mL/min/1.73 m2], and 40 with advanced CKD from the observational Cardiovascular Comorbidity in Children with Chronic Kidney Disease (4C) study (eGFR 24 mL/min/1.73 m2). In each study, vitamin D supplementation was started in 20 children and 20 matched children not receiving vitamin D served as controls. Measures were taken at baseline and after a median period of 8 months. Age- and gender-related standard deviation scores (SDSs) were calculated. Results: Before vitamin D supplementation, children in the ERGO study had normal FGF23 (median 0.31 SDS) and BAP (-0.10 SDS) but decreased Klotho and sclerostin (-0.77 and -1.04 SDS, respectively), whereas 4C patients had increased FGF23 (3.87 SDS), BAP (0.78 SDS) and sclerostin (0.76 SDS) but normal Klotho (-0.27 SDS) levels. Vitamin D supplementation further increased FGF23 in 4C but not in ERGO patients. Serum Klotho and sclerostin normalized with vitamin D supplementation in ERGO but remained unchanged in 4C patients. BAP levels were unchanged in all patients. In the total cohort, significant effects of vitamin D supplementation were noted for Klotho at eGFR 40-70 mL/min/1.73 m2. Conclusions: Vitamin D supplementation normalized Klotho and sclerostin in children with mild to moderate CKD but further increased FGF23 in advanced CKD.