Klinefelter Bone Microarchitecture Evolution with Testosterone Replacement Therapy

Klinefelter Syndrome (KS) patients, defined by a 47 XXY karyotype, have increased risk of fragility fractures. We have assessed bone microarchitecture by high resolution peripheral quantitative CT (HR-pQCT) at the radius and tibia in young KS patients, naïve from testosterone replacement therapy (TRT). Areal bone mineral density (BMD) and body composition were assessed by dual X-ray absorptiometry (DXA). Total testosterone (tT) was measured at baseline. Bone measurements have been repeated after 30 months of TRT. We enrolled 24 KS patients and 72 age-matched controls. KS patients were (mean ± SD) 23.7 ± 7.8 year-old. KS patients had significantly lower relative appendicular lean mass index (RALM) and lower aBMD at spine and hip than controls. Ten patients (42%) had low tT level (≤ 10.4 nmol/L). At baseline, we observed at radius a marked cortical (Ct) impairment reflected by lower Ct.area, Ct.perimeter, and Ct.vBMD than controls. At tibia, in addition to cortical fragility, we also found significant alterations of trabecular (Tb) compartment with lower trabecular bone volume (BV/TV) and Tb.vBMD as compared to controls. After 30 months of TRT, 18 (75%) KS patients were reassessed. Spine aBMD and RALM significantly increased. At radius, both cortical (Ct.Pm, Ct.Ar, Ct.vBMD, Ct.Th) and trabecular (Tb.vBMD) parameters significantly improved. At tibia, the improvement was found only in the cortical compartment. Young TRT naïve KS patients have inadequate bone microarchitecture at both the radius and tibia, which can improve on TRT.

Fluconazole in hypercalciuric patients with increased 1,25(OH)2D levels: the prospective, randomized, placebo-controlled, double-blind FLUCOLITH trial

Background

Hypercalciuria is one of the most frequent metabolic disorders associated with nephrolithiasis and/or nephrocalcinosis possibly leading to chronic kidney disease (CKD) and bone complications in adults. Orphan diseases with different underlying primary pathophysiology share inappropriately increased 1,25(OH)₂D levels and hypercalciuria, e.g., hypersensitivity to vitamin D and renal phosphate wasting. Their management is challenging, typically based on hyperhydration and dietary advice.

The antifungal azoles are known to inhibit the 1α-hydroxylase and therefore decrease 1,25(OH)₂D levels; they are commonly used, with well described pharmacokinetic and tolerability data. Fluconazole has been successfully reported to reduce calciuria in patients with CYP24A1 or SLC34A3 mutations, with no safety warnings. Thus, based on these case reports, we hypothesize that fluconazole is effective to decrease and normalize calciuria in patients with hypercalciuria and increased 1,25(OH)₂D levels.

Methods

The FLUCOLITH trial is a prospective, interventional, randomized in parallel groups (1:1), placebo-controlled, double-blind trial. A total of 60 patients (10–60 years) with nephrolithiasis and/or nephrocalcinosis history, hypercalciuria (> 0.1 mmol/kg/day), increased 1,25(OH)₂D levels (> 150 pmol/L), and 25-OH-D levels >20 nmol/L will be included. Inclusions will be performed only from mid-September to the beginning of February to avoid bias due to sunlight-induced vitamin D synthesis. The primary endpoint will be the proportion of patients with normalization of 24-h calciuria between baseline and 16 weeks, or with a relative decrease of at least 30% of 24-h calciuria in patients who still display at W16 a 24-h hypercalciuria.

Discussion

The current challenge is to propose an efficient treatment to patients with hypercalciuria and increased 1,25(OH)₂D levels in order to prevent later complications and notably CKD that can ultimately lead to end-stage renal disease. Based on improvement of knowledge in phosphate/calcium metabolism, pathophysiology and genetics, the “off-label” use of fluconazole was recently reported to be useful in hypercalciuric patients with increased 1,25(OH)₂D levels. Thus, the FLUCOLITH study is a unique opportunity to develop a new indication of a well-known and not expensive drug in orphan renal diseases, the ultimate objective being the secondary prevention of CKD worsening in these patients.

Trial registration

ClinicalTrials.gov NCT04495608. Registered on July 23, 2020.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-022-06302-z.

[Cholecalciferol (vitamin D3) must not be considered as an endocrine disruptor]

A French ministerial decree planning to include cholecalciferol, i.e. vitamin D3 (VD3), in the endocrine disruptors (ED) list has generated a lot of concerns in French physicians and scientists. The aim of the present article was to discuss the scientific rationale that may support or not this decision, which seems to be due to the use of VD3 overdose as a rodenticide in some European countries. First, it is noticeable that cholecalciferol is not an “exogenous substance”, a term used in all the definitions of ED, as it is largely synthesized in the skin after UVB rays exposure. Second, we did not find any published article that may support the inclusion of VD3 in the ED list. The request “vitamin D AND endocrine disruptor” reported 33 references in the PubMed database on March, 10, 2022, most of them discussing disturbances of vitamin D metabolism by EDs. Third, a large amount of studies conclude that VD3 has or may have beneficial effects on many functions that are known to be altered by EDs. In addition, we warn that learning that VD3 could be legally considered as a PE may cause the general public to mistrust vitamin D supplementation, which is not desirable in terms of public health as it may increase the already too high prevalence of vitamin D deficient individuals. We consider the aberrant decision of including cholecalciferol in the ED list should be rapidly invalidated before being effective in France and possibly disseminated in the European Union.

Teenagers and young adults with a past of allogenic hematopoietic stem cell transplantation are at significant risk of chronic kidney disease

BACKGROUND

Allogenic hematopoietic stem cell transplantation (aHSCT) remains the treatment of choice for some malignant hemopathies in children, albeit with the risk of long-term consequences, including chronic kidney disease (CKD).

METHODS

In our single tertiary referral center, we retrospectively assessed the long-term renal outcome in a cohort of children and adolescents who had undergone aHSCT for malignant hemopathies between 2003 and 2017. We distinguished glomerular and tubular dysfunctions and assessed the accuracy of the most common formula(s) to estimate glomerular filtration rate (GFR) during standard clinical follow-up.

RESULTS

Among the 166 patients who had received aHSCT, 61 underwent kidney functional assessment 1 to 10 years post-transplantation. Twenty-seven patients (44.3%) had a CKD with glomerular impairment, including 20 patients with a GFR < 90 mL/min/1.73 m², and among these, 5 patients < 60 mL/min/1.73 m². Patients with tubular signs had a significantly higher baseline GFR: 112 mL/min/1.73 m² [100; 120] versus 102 [99.0; 112.5] for patients without kidney involvement, and 76 [61; 86] for patients with CKD (p < 0.01). Schwartz, CKiDU25, and EKFC formulas significantly overestimated mGFR, with a P30% ≤ 30%, which could lead to overlooking CKD diagnosis in this population. No patient reached kidney failure.

CONCLUSIONS

In conclusion, our study shows that CKD represents an important long-term sequela for children and adolescents who undergo aHSCT for malignant hemopathies, either with glomerular dysfunction or with the more insidious tubular dysfunction which could potentially impact growth. These patients could benefit from specialized long-term nephrology follow-up. A higher resolution version of the Graphical abstract is available as Supplementary information.

Primary hyperoxaluria type 1: novel therapies at a glance

Primary hyperoxaluria type 1 (PH1) is a rare and severe autosomal recessive disease of oxalate metabolism, resulting from a mutation in the AGXT gene that encodes the hepatic peroxisomal enzyme alanine–glyoxylate aminotransferase (AGT). Until recently, treatment of PH1 was supportive, consisting of intensive hyperhydration, use of crystallization inhibitors (citrate and neutral phosphorus), in a subset of responsive PH1 patients’ pharmacologic doses of vitamin B6 (pyridoxine), and kidney and liver transplantation when patients progressed to kidney failure. Treatment approaches have been similar for PH2 caused by mutations in hepatic glyoxylate reductase/hydroxypyruvate reductase (GR/HPR), although pyridoxine does not have any benefit in this group. PH3 is caused by mutations of mitochondrial 4-hydroxy-2-oxoglutarate aldolase (HOGA1) and was the most recently described. Kidney failure appears less common in PH3, although kidney stones occur as frequently as in PH1 and PH2. Oxalate metabolism in the liver is complex. Novel therapies based on RNA interference (RNAi) have recently emerged to modulate these pathways, designed to deplete substrate for enzymes upstream and decrease/avoid oxalate production. Two hepatic enzymes have been targeted to date in PH: glycolate oxidase (GO) with lumasiran and lactate dehydrogenase A (LDH-A) with nedosiran. Lumasiran was approved for the treatment of PH1 in 2020 by both the European Medicines Agency and the Food and Drug Administration, whilst clinical trials with nedosiran are ongoing. Results with the two RNAi therapies demonstrate a significant reduction of urinary oxalate excretion in PH1 patients, but long-term data on efficacy (preservation of kidney function, decreased stone events) and safety remain to be established. Nevertheless, the hepatically targeted RNAi approach represents a potential ‘game changer’ in the field of PH1, bringing hope to families and patients that they may be able to avoid liver and/or kidney transplantation in the future and suffer fewer stone events, perhaps with less strict therapeutic regimens. Pharmacological compounds directly inhibiting GO or LDH are also under development and could be of special interest in developing countries where RNAi therapies may not be readily available in the near future. Approaches to manipulate the intestinal microbiome with a goal to increase oxalate degradation or to stimulate secretion of oxalate into the intestine from plasma are also under development. Overall, we appear to be entering a new phase of PH treatment, with an array of promising approaches emerging that will need optimization and evaluation to establish long-term efficacy and safety.

Idiopathic nephrotic syndrome relapse following SARS-CoV-2 vaccination: a series of 25 cases

Background

Several cases of idiopathic nephrotic syndrome (INS) relapse following the administration of coronavirus disease 2019 (COVID-19) vaccines have recently been reported, raising questions about the potential relationship between the immune response to COVID-19 vaccination and INS pathogenesis.

Methods

We performed a retrospective multicentre survey describing the clinical and biological characteristics of patients presenting a relapse of INS after COVID-19 vaccination, with an assessment of outcome under treatment.

Results

We identified 25 patients (16 men and 9 women) presenting a relapse within 1 month of a COVID-19 vaccine injection. The glomerular disease was of childhood onset in half of the patients and most patients (21/25) had received at least one immunosuppressive drug in addition to steroids for frequently relapsing or steroid-dependent nephrotic syndrome (NS). All patients were in a stable condition at the time of injection and 11 had no specific treatment. In five patients, the last relapse was reported >5 years before vaccine injection. The Pfizer-BioNTech (BNT162b2) vaccine was used in 80% of the patients. In 18 cases, INS relapse occurred after the first injection, a mean of 17.5 days after vaccination. A second injection was nevertheless administered in 14 of these patients. Five relapses occurred after administration of the second dose and two relapses after the administration of the third dose. All but one of the patients received steroids as first-line treatment, with an additional immunosuppressive agent in nine cases. During follow-up, complete remission was achieved in 21 patients, within 1 month in 17 cases. Only one patient had not achieved at least partial remission after 3 months of follow-up.

Conclusions

This case series suggests that, in rare patients, COVID-19 vaccination may trigger INS relapse that is generally easy to control. These findings should encourage physicians to persuade their patients to complete the COVID-19 vaccination schedule.

Vitamin D and calcium intakes in general pediatric populations: A French expert consensus paper

OBJECTIVES

Nutritional vitamin D supplements are often used in general pediatrics. Here, the aim is to address vitamin D supplementation and calcium nutritional intakes in newborns, infants, children, and adolescents to prevent vitamin D deficiency and rickets in general populations.

STUDY DESIGN

We formulated clinical questions relating to the following categories: the Patient (or Population) to whom the recommendation will apply; the Intervention being considered; the Comparison (which may be "no action," placebo, or an alternative intervention); and the Outcomes affected by the intervention (PICO). These PICO elements were arranged into the questions to be addressed in the literature searches. Each PICO question then formed the basis for a statement. The population covered consisted of children aged between 0 and 18 years and premature babies hospitalized in neonatology. Two groups were assembled: a core working group and a voting panel from different scientific pediatric committees from the French Society of Pediatrics and national scientific societies.

RESULTS

We present here 35 clinical practice points (CPPs) for the use of native vitamin D therapy (ergocalciferol, vitamin D2 and cholecalciferol, vitamin D3) and calcium nutritional intakes in general pediatric populations.

CONCLUSION

This consensus document was developed to provide guidance to health care professionals on the use of nutritional vitamin D and dietary modalities to achieve the recommended calcium intakes in general pediatric populations. These CPPs will be revised periodically. Research recommendations to study key vitamin D outcome measures in children are also suggested.

The effect of lumasiran therapy for primary hyperoxaluria type 1 in small infants

BACKGROUND

Lumasiran, a sub-cutaneous RNA-interference therapy, has been recently approved for primary hyperoxaluria type 1 (PH1), with doses and intervals according to body weight. Little is known as to its use in infants; the aim of this study was to describe treatment outcome in 3 infants who received lumasiran therapy before 2 years of age.

CASE-DIAGNOSIS/TREATMENT

Patient 1 was diagnosed antenatally and received lumasiran from day 9. According to the product information template (PIT), he received monthly lumasiran (3 times at 6 mg/kg, then 3 mg/kg), with hyperhydration and potassium citrate. Despite decreased plasma oxalate levels, persistent normal kidney function, and good tolerance, kidney ultrasound performed after 2 months found nephrocalcinosis, without normalization of urinary oxalate (UOx). The dose was increased back to 6 mg/kg, inducing a normalization in UOx. Nephrocalcinosis started to improve at month 10. Patient 2 was diagnosed at 2.5 months (acute kidney failure); nephrocalcinosis was present from diagnosis. She received monthly lumasiran (6 mg/kg), with progressive decrease in UOx and substantial improvement in kidney function but stable nephrocalcinosis after 9 injections. Patient 3 was diagnosed fortuitously (nephrocalcinosis) at 3.5 months and received lumasiran before genetic diagnosis, leading to decreased UOx and maintenance of normal kidney function. Nephrocalcinosis improved after 5 injections.

CONCLUSIONS

This report presents the youngest children treated with lumasiran worldwide. Lumasiran seems effective without side effects in infants but does not completely prevent the onset of nephrocalcinosis in the most severe forms. Higher doses than those proposed in the PIT might be required because of hepatic immaturity.

Parathyroid hormone and phosphate homeostasis in patients with Bartter and Gitelman syndrome: an international cross-sectional study

BACKGROUND

Small cohort studies have reported high parathyroid hormone (PTH) levels in patients with Bartter syndrome and lower serum phosphate levels have anecdotally been reported in patients with Gitelman syndrome. In this cross-sectional study, we assessed PTH and phosphate homeostasis in a large cohort of patients with salt-losing tubulopathies.

METHODS

Clinical and laboratory data of 589 patients with Bartter and Gitelman syndrome were provided by members of the European Rare Kidney Diseases Reference Network (ERKNet) and the European Society for Paediatric Nephrology (ESPN).

RESULTS

A total of 285 patients with Bartter syndrome and 304 patients with Gitelman syndrome were included for analysis. Patients with Bartter syndrome type I and II had the highest median PTH level (7.5 pmol/L) and 56% had hyperparathyroidism (PTH >7.0 pmol/L). Serum calcium was slightly lower in Bartter syndrome type I and II patients with hyperparathyroidism (2.42 versus 2.49 mmol/L; P = .038) compared to those with normal PTH levels and correlated inversely with PTH (rs -0.253; P = .009). Serum phosphate and urinary phosphate excretion did not correlate with PTH. Overall, 22% of patients had low serum phosphate levels (phosphate-standard deviation score < -2), with the highest prevalence in patients with Bartter syndrome type III (32%). Serum phosphate correlated with tubular maximum reabsorption of phosphate/glomerular filtration rate (TmP/GFR) (rs 0.699; P < .001), suggesting renal phosphate wasting.

CONCLUSIONS

Hyperparathyroidism is frequent in patients with Bartter syndrome type I and II. Low serum phosphate is observed in a significant number of patients with Bartter and Gitelman syndrome and appears associated with renal phosphate wasting.

Severe neonatal hypercalcemia revealing congenital mesoblastic nephroma: A case report and management of neonatal hypercalcemia: Severe neonatal hypercalcemia revealing congenital mesoblastic nephroma

Congenital mesoblastic nephroma is a rare pediatric renal tumor and has been reported in patients presenting with palpable abdominal mass, arterial hypertension, hematuria, polyuria, or hypercalcemia. Here we present the case of a 1-month-old neonate with suspected parathyroid hormone (PTH)-related peptide (PTH-rp)-mediated severe hypercalcemia revealing congenital mesoblastic nephroma. Preoperatively, hypercalcemia was corrected with hydration, furosemide, pamidronate, and low-calcium infant formula. Unilateral nephrectomy led to the resolution of hypercalcemia, transient hyperparathyroidism, and transient vitamin D and mineral supplementation. We conclude that congenital mesoblastic nephroma can secrete PTH-rp that can cause severe hypercalcemia.

To biopsy or not to biopsy: Henoch-Schönlein nephritis in children, a 5-year follow-up study

BACKGROUND

The prognosis of Henoch-Schönlein purpura (HSP), IgA vasculitis, depends on kidney involvement. There is no consensus on the initiation of treatment for HSP nephritis (HSPN). Some centres start treatment before performing a kidney biopsy (KB) while in others, treatment is dictated by the importance of the clinical, biological and histological signs. The aim of this study was to evaluate which of these two approaches is associated with a better kidney outcome at 5-year follow-up.

METHODS

This multicentre, retrospective, nonrandomised study included children treated for HSPN between 2006 and 2010 in a French paediatric nephrology unit. One group had an early KB at diagnosis (before starting treatment or in the 15 following days). In the second group, initial treatment was decided without performing a KB.

RESULTS

Among the 107 children included, 63.5% had an early KB at diagnosis. Follow-up at 5 years was completed in 44 children (28 KB at diagnosis, 16 no KB at diagnosis). Median urine protein/creatinine at 5 years was 2.5 mg/mmol in the early biopsy diagnosis group and 12.5 mg/mmol in the non-biopsy group. An antiproteinuric treatment was given, at 5 years, to 35.7% of the early biopsy at diagnosis children and in 62.5% of the non-biopsied children.

CONCLUSIONS

Children with early KB at diagnosis seem to have a better renal outcome at 5 years compared to those without an early biopsy at diagnosis or biopsied later. However, this is a small patient cohort and data are missing. Further work is needed to build consensual guidelines on the management of HSPN in children.

An Expert Perspective on Phosphate Dysregulation With a Focus on Chronic Hypophosphatemia

Because of their rarity, diseases characterized by chronic hypophosphatemia can be underrecognized and suboptimally managed, resulting in poor clinical outcomes. Moreover, serum phosphate may not be measured routinely in primary care practice. Authors participated in several working sessions to advance the understanding of phosphate homeostasis and the causes, consequences, and clinical implications of chronic hypophosphatemia. Phosphate levels are regulated from birth to adulthood. Dysregulation of phosphate homeostasis can result in hypophosphatemia, which becomes chronic if phosphate levels cannot be normalized. Chronic hypophosphatemia may be underrecognized as serum phosphate measurement is not always part of routine analysis in the primary care setting and results might be misinterpreted, for instance, due to age-specific differences not being accounted for and circadian variations. Clinical consequences of chronic hypophosphatemia involve disordered endocrine regulation, affect multiple organ systems, and vary depending on patient age and the underlying disorder. Signs and symptoms of chronic hypophosphatemic diseases that manifest during childhood or adolescence persist into adulthood if the disease is inadequately managed, resulting in an accumulation of clinical deficits and a progressive, debilitating impact on quality of life. Early identification and diagnosis of patients with chronic hypophosphatemia is crucial, and clinical management should be started as soon as possible to maximize the likelihood of improving health outcomes. Furthermore, in the absence of a universally accepted description for "chronic hypophosphatemia," a definition is proposed here that aims to raise awareness of these diseases, facilitate diagnosis, and guide optimal phosphate management strategies by improving monitoring and assessment of patient response to treatment. © 2021 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

OUP accepted manuscript

Oxalate crystals in the kidney were first described in 1925. Since then, many major milestones have been reached in the understanding of genetic primary hyperoxaluria(s). Primary hyperoxaluria type 1 (PH1) is an autosomal recessive disease due to a mutation in the AGXT gene, which encodes the hepatic peroxisomal enzyme alanine-glyoxylate aminotransferase (AGT), inducing excess oxalate production and further kidney stones, nephrocalcinosis and chronic kidney disease (CKD). Symptoms and age at diagnosis of PH1 vary dramatically, from the most severe infantile forms leading to end-stage kidney disease (ESKD) during the first months of life to the less severe adult forms with moderate CKD and recurrent kidney stones. In 2020, the Food and Drug Administration (FDA) and European Medicines Agency (EMA) approved a therapy based on RNA interference (RNAi) that profoundly reduces endogenous oxalate synthesis and dramatically changes the treatment algorithm for patients with PH1. The aim of this supplement of Clinical Kidney Journal includes contemporary reviews of the pathophysiology and genetics, (conventional) medical therapeutic management, urological therapeutic management and novel therapies (including not only RNAi, but also other therapeutic perspectives). The specific opinions of both adult and paediatric nephrologists will be compared and the ethical issues, as well as challenges faced by physicians and patients in developing countries, will also be discussed. Despite all the accomplishments, there are still looming questions that require further investigation and discovery.

Off-label use of cinacalcet in pediatric primary hyperparathyroidism: A French multicenter experience

BACKGROUND

Cinacalcet is a calcimimetic approved in adults with primary hyperparathyroidism (PHPT). Few cases reports described its use in pediatric HPT, with challenges related to the risk of hypocalcemia, increased QT interval and drug interactions. In this study, we report the French experience in this setting.

METHODS

We retrospectively analyzed data from 18 pediatric patients from 7 tertiary centers who received cinacalcet for PHPT. The results are presented as median (interquartile range).

RESULTS

At a median age of 10.8 (2.0-14.4) years, 18 patients received cinacalcet for primary HPT (N = 13 inactive CASR mutation, N = 1 CDC73 mutation, N = 1 multiple endocrine neoplasia type 1, N=3 unknown etiology). Cinacalcet was introduced at an estimated glomerular filtration rate (eGFR) of 120 (111-130) mL/min/1.73 m², plasma calcium of 3.04 (2.96-3.14) mmol/L, plasma phosphate of 1.1 (1.0-1.3) mmol/L, age-standardized (z score) phosphate of -3.0 (-3.5;-1.9), total ALP of 212 (164-245) UI/L, 25-OHD of 37 (20-46) ng/L, age-standardized (z score) ALP of -2.4 (-3.7;-1.4), PTH of 75 (59-123) ng/L corresponding to 1.2 (1.0-2.3)-time the upper limit for normal (ULN). The starting daily dose of cinacalcet was 0.7 (0.6-1.0) mg/kg, with a maximum dose of 1.0 (0.9-1.4) mg/kg per day. With a follow-up of 2.2 (1.3-4.3) years on cinacalcet therapy, PTH and calcium significantly decreased to 37 (34-54) ng/L, corresponding to 0.8 (0.5-0.8) ULN (p = 0.01), and 2.66 (2.55-2.90) mmol/L (p = 0.002), respectively. In contrast, eGFR, 25-OHD, ALP and phosphate and urinary calcium levels remained stable. Nephrocalcinosis was not reported but one patient displayed nephrolithiasis. Cinacalcet was progressively withdrawn in three patients; no side effects were reported.

CONCLUSIONS

Cinacalcet in pediatric HPT can control hypercalcemia and PTH without significant side effects.

Local protocol helped to deliver vitamin D levels more accurately in preterm infants

AIM

This study retrospectively evaluated the effectiveness and safety of a local hospital protocol of vitamin D supplementation for preterm infants, which was modified in 2016.

METHODS

We focussed on 99 preterm infants born before 31 weeks of gestation and admitted to the neonatal intensive care unit at the Femme Mere Enfant Hospital, Bron, France, from 1 January to 31 December 2018. Calcium and urinary calcium were measured, and 25-hydroxy vitamin D (25(OH)D) levels were monitored monthly and supplementation was adjusted, with 50-120 nmol/L considered normal. The results are presented as medians and interquartile ranges.

RESULTS

The infants were enrolled at a gestational age of 28.0 [26.9-29.1] weeks and birth weight of 960 [800-1160] g. When they were discharged at 37.3 [35.2-39.8] weeks, the overall 25(OH)D level was 98 [79-140] nmol/L: 4% had low levels, 63% had normal levels and 33% had high levels. Vitamin D supplementation was withdrawn for 60% more than one month before discharge. Rickets or fractures were not reported.

CONCLUSION

The modified protocol limited underdosing and significant overdosing, but moderate hypervitaminosis D was still frequent. Urgent studies are needed to determine the optimal supplementation and clinical impact of 25(OH)D on comorbidities in preterm infants.

Nephrocalcinosis in very low birth weight infants: incidence, associated factors, and natural course

BACKGROUND

Preterm kidney is exposed to various exogenous factors that may impact its function such as nephrotoxic drugs or nephrocalcinosis. We investigated prevalence and risk factors of nephrocalcinosis (NC) in recently born very low birth weight (VLBW) infants submitted to improved biological monitoring.

METHODS

Retrospective, case-control study in very preterm infants (< 32 + 6 weeks, ≤ 1500 g) admitted to a tertiary care unit during a 6-year period. Each case (ultrasound-diagnosed NC) was matched with two controls (no NC). Data were collected at days 15 and 30 of life and 35 weeks corrected age, with follow-up at 18 months and 3 years.

RESULTS

Of 525 eligible infants, overall prevalence of NC was 17.1% at 35 weeks corrected age. Prevalence was halved between 2012 (26.1%) and 2017 (11.8%). We included 265 infants, more than half being born before 28 weeks. Cases presented with more severe morbidity than controls, but reached statistical significance only in infants born < 28 weeks (88.2% vs. 68.3%, P = 0.01). Protein, energy, calcium, phosphorus, and vitamin D intakes were similar in the two groups and did not change significantly over the study period. Weight gain was similar in the two groups. Exposure to furosemide (OR [IC95%]: 1.26 [1.02; 1.57]) and postnatal growth (1.65 [1.04; 2.67]) were independent risk factors of NC. NC resolved 12-18 months after diagnosis in 61% of infants.

CONCLUSION

Prevalence of NC is significant but can be reduced. Furosemide should be cautiously prescribed in VLBW infants, and nutritional support must be well monitored to support postnatal growth and limit risk of nephrocalcinosis.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT 04,860,583. A higher resolution version of the Graphical abstract is available as Supplementary information.

Composition of urinary stones in children: clinical and metabolic determinants in a French tertiary care center

As the epidemiology of urolithiasis is constantly evolving, analyzing the composition of stones is crucial to better understand the determinants of lithogenesis. The aim of this study was to describe the composition of stones of pediatric patients in a tertiary center. Clinical and metabolic data from all pediatric patients with at least one stone that was analyzed by Fourier transformed infrared spectroscopy (FTIR) in the Hospices Civils de Lyon between 2013 and 2017 were retrospectively collected. A total of 111 patients (sex ratio 1.4:1) were included; their median ([IQR]) age was 7.5 (3.1-10.5) years. The main component of stones was calcium oxalate (weddellite for 34 (31%) stones, whewellite 23 (21%)), calcium phosphate (carbapatite 32 (29%), brushite 6 (5%), amorphous calcium phosphate 3 (3%)), struvite 5 (5%), cystine 4 (4%), uric acid 2 (2%), and ammonium acid urate 2 (2%). A total of 20 (18%) stones were pure and 24 (22%) were infectious. Carbapatite stones were the most frequent in patients < 2 years and calcium oxalate stones in patients > 2 years old. Metabolic abnormalities (most frequently hypercalciuria) were found in 50% of tested patients and in 54% of patients with infectious stones. Congenital anomalies of the kidney and/or urinary tract (CAKUT) or neurogenic bladder were present in 9/24 (38%) patients with infectious stones and 12/16 (76%) patients with bladder stones.Conclusion: This study confirms that calcium oxalate stones are the most frequent among pediatric patients, which could reflect the nutritional habits of predisposed patients. In contrast, infectious stones are less frequent and occur mostly in association with anatomic or metabolic favoring factors.

Peripheral Blood Mononuclear Cells (PBMCs) to Dissect the Underlying Mechanisms of Bone Disease in Chronic Kidney Disease and Rare Renal Diseases

PURPOSE OF REVIEW

To describe the methods that can be used to obtain functional and mature osteoclasts from peripheral blood mononuclear cells (PBMCs) and report the data obtained with this model in two peculiar diseases, namely pediatric chronic kidney disease-associated mineral and bone disorders (CKD-MBD) and nephropathic cystinosis. To discuss future research possibilities in the field.

RECENT FINDINGS

Bone tissue undergoes continuous remodeling throughout life to maintain bone architecture; it involves two processes: bone formation and bone resorption with the coordinated activity of osteoblasts, osteoclasts, and osteocytes. Animal models fail to fully explain human bone pathophysiology during chronic kidney disease, mainly due to interspecies differences. The development of in vitro models has permitted to mimic human bone-related diseases as an alternative to in vivo models. Since 1997, osteoclasts have been generated in cell cultures, notably when culturing PBMCs with specific growth factors and cytokines (i.e., M-CSF and RANK-L), without the need for osteoblasts or stromal cells. These models may improve the global understanding of bone pathophysiology. They can be been used not only to evaluate the direct effects of cytokines, hormones, cells, or drugs on bone remodeling during CKD-MBD, but also in peculiar genetic renal diseases inducing specific bone impairment.

TmP/GFR reference values from childhood to adulthood in the era of IDMS-standardized creatinine values

BACKGROUND

The assessment of phosphate homeostasis in clinical practice relies on circulating phosphate levels but also on phosphate tubular reabsorption, ideally assessed using the Tubular maximum Phosphate Reabsorption per Glomerular Filtration Rate (TmP/GFR). TmP/GFR reference values were established before the onset of IDMS-standardized creatinine assays, and thus need to be updated. Our objective is to provide reference values for TmP/GFR from childhood to adulthood, using the gold-standard of GFR assessment and IDMS-standardized creatinine values.

METHODS

We retrospectively analyzed all the inulin and iohexol clearances (mGFR) performed in children and in adults screened for a living-donation in our unit since the beginning of IDMS-creatinine assays. TmP/GFR was calculated on a fasting sample, using the conventional formula without correction for TRP in subjects below 19 years of age.

RESULTS

A total of 2051 subjects (1711 children, 340 adults), aged from 1.9 to 73.4 years with normal GFR, normal phosphate and normal calcium levels, was included for TmP/GFR analysis. As expected, there was a progressive decrease along puberty in both genders of plasma phosphate and TmP/GFR, the decrease occurring earlier in girls. After the age of 19, there was a stabilization of plasma phosphate and TmP/GFR levels until the age of 55, phosphate levels and TmP/GFR being slightly lower in men than in women.

CONCLUSION

We present the largest cohort describing TmP/GFR reference values in the era of IDMS-standardized creatinine assays. We believe that these data will help physicians to better diagnose and manage patients with abnormal phosphate metabolism in daily clinical routine.

Long-Term Transplantation Outcomes in Patients With Primary Hyperoxaluria Type 1 Included in the European Hyperoxaluria Consortium (OxalEurope) Registry

Introduction

In primary hyperoxaluria type 1 (PH1), oxalate overproduction frequently causes kidney stones, nephrocalcinosis, and kidney failure. As PH1 is caused by a congenital liver enzyme defect, combined liver–kidney transplantation (CLKT) has been recommended in patients with kidney failure. Nevertheless, systematic analyses on long-term transplantation outcomes are scarce. The merits of a sequential over combined procedure regarding kidney graft survival remain unclear as is the place of isolated kidney transplantation (KT) for patients with vitamin B6-responsive genotypes.

Methods

We used the OxalEurope registry for retrospective analyses of patients with PH1 who underwent transplantation. Analyses of crude Kaplan–Meier survival curves and adjusted relative hazards from the Cox proportional hazards model were performed.

Results

A total of 267 patients with PH1 underwent transplantation between 1978 and 2019. Data of 244 patients (159 CLKTs, 48 isolated KTs, 37 sequential liver–KTs [SLKTs]) were eligible for comparative analyses. Comparing CLKTs with isolated KTs, adjusted mortality was similar in patients with B6-unresponsive genotypes but lower after isolated KT in patients with B6-responsive genotypes (adjusted hazard ratio 0.07, 95% CI: 0.01–0.75, P = 0.028). CLKT yielded higher adjusted event-free survival and death-censored kidney graft survival in patients with B6-unresponsive genotypes (P = 0.025, P < 0.001) but not in patients with B6-responsive genotypes (P = 0.145, P = 0.421). Outcomes for 159 combined procedures versus 37 sequential procedures were comparable. There were 12 patients who underwent pre-emptive liver transplantation (PLT) with poor outcomes.

Conclusion

The CLKT or SLKT remains the preferred transplantation modality in patients with PH1 with B6-unresponsive genotypes, but isolated KT could be an alternative approach in patients with B6-responsive genotypes.

Orthopedic and neurosurgical care of X-linked hypophosphatemia

X-linked hypophosphatemia (XLH) is due to mutations in the PHEX gene leading to unregulated production of FGF23 and uncontrollable hypophosphatemia. XLH is characterized in children by rickets, short stature, waddling gait, and leg bowing of variable morphology and severity. Phosphate supplements and oral vitamin D analogs partially or, in some cases, fully restore the limb straightness. XLH patients may also be affected by premature, complete, or partial ossification of sutures between cranial bone, which could eventually result in cranial dysmorphia, decreased intracranial volume, and secondary abnormally high intracranial pressure with a cerebral compression. Our goal is to address the criteria and the management of the skeletal complications associated with XLH, mainly orthopedic and neurosurgical care, and reflect on decision-making and follow-up complexities.

Demographic Characteristics, Risk Factors, and Presenting Features of Children with Symptomatic Nutritional Rickets: A French Series

AIM

To describe the demographic characteristics, risk factors, and presenting features of children with symptomatic nutritional rickets in France.

METHODS

This is a retrospective study of 38 children diagnosed with nutritional rickets from 1998 to 2019.

RESULTS

We observed a higher frequency of rickets in males (74 vs. 26%), in young children (median age at diagnosis: 23 months; 82% were younger than 5 years), and in children with a non-Caucasian ethnic background (89%). Most children were exclusively breastfed (78%) without adequate vitamin D supplementation (89%). The most common presentations were bowed legs (63%), hypocalcemic seizures (21%), and growth retardation (11%). Approximately half (62%) of the children were hypocalcemic. The children presenting with hypocalcemic seizures were significantly younger (0.8 vs. 2.2 years; p = 0.041) and had lower total serum calcium levels (1.44 vs. 2.17 mmol/L; p < 0.0001), higher phosphatemia (1.43 vs. 1.23 mmol/L; p = 0.020), and lower 25-hydroxy vitamin D levels (3 vs. 7 ng/mL; p = 0.020) but similar parathyroid hormone levels (357 vs. 289 ng/mL; p = 0.940) compared to rickets cases who did not experience hypocalcemic seizures. A dilated cardiomyopathy was detected in 14% of the children who had undergone echocardiography.

CONCLUSION

Nutritional rickets remains endemic in the pediatric population and its most severe forms can have life-threatening sequelae. Health practitioners need to be cognizant of these facts to raise awareness and screen high-risk populations.

Hemodiafiltration Is Associated With Reduced Inflammation and Increased Bone Formation Compared With Conventional Hemodialysis in Children: The HDF, Hearts and Heights (3H) Study

Background

Patients on dialysis have a high burden of bone-related comorbidities, including fractures. We report a post hoc analysis of the prospective cohort study HDF, Hearts and Heights (3H) to determine the prevalence and risk factors for chronic kidney disease-related bone disease in children on hemodiafiltration (HDF) and conventional hemodialysis (HD).

Methods

The baseline cross-sectional analysis included 144 children, of which 103 (61 HD, 42 HDF) completed 12-month follow-up. Circulating biomarkers of bone formation and resorption, inflammatory markers, fibroblast growth factor-23, and klotho were measured.

Results

Inflammatory markers interleukin-6, tumor necrosis factor-α, and high-sensitivity C-reactive protein were lower in HDF than in HD cohorts at baseline and at 12 months (P < .001). Concentrations of bone formation (bone-specific alkaline phosphatase) and resorption (tartrate-resistant acid phosphatase 5b) markers were comparable between cohorts at baseline, but after 12-months the bone-specific alkaline phosphatase/tartrate-resistant acid phosphatase 5b ratio increased in HDF (P = .004) and was unchanged in HD (P = .44). On adjusted analysis, the bone-specific alkaline phosphatase/tartrate-resistant acid phosphatase 5b ratio was 2.66-fold lower (95% confidence interval, −3.91 to −1.41; P < .0001) in HD compared with HDF. Fibroblast growth factor-23 was comparable between groups at baseline (P = .52) but increased in HD (P < .0001) and remained unchanged in HDF (P = .34) at 12 months. Klotho levels were similar between groups and unchanged during follow-up. The fibroblast growth factor-23/klotho ratio was 3.86-fold higher (95% confidence interval, 2.15–6.93; P < .0001) after 12 months of HD compared with HDF.

Conclusion

Children on HDF have an attenuated inflammatory profile, increased bone formation, and lower fibroblast growth factor-23/klotho ratios compared with those on HD. Long-term studies are required to determine the effects of an improved bone biomarker profile on fracture risk and cardiovascular health.

Chronic kidney disease consecutive to chemotherapy for chondroblastic osteosarcoma: A report on 6 pediatric cases

BACKGROUND

The management of osteosarcoma in children and adolescents is based on poly-chemotherapy including several nephrotoxic drugs (e.g. ifosfamide, methotrexate, and cisplatinum). Chronic renal toxicity is a frequent complication but stage 5 chronic kidney disease requiring dialysis is rare. We report here a series of six pediatric patients with osteosarcoma displaying chronic kidney disease after chemotherapy.

CASE-DIAGNOSIS/TREATMENT

We retrospectively reviewed the medical charts, mainly for clinical history, timing between chemotherapy and development of tubulopathy and CKD, type of therapies and global evolution (chronic dialysis and further renal transplantation, n=2; death, n=1). Notably, all patients suffered from chondroblastic osteosarcoma.

CONCLUSIONS

Advanced chronic kidney disease can be a complication of osteosarcoma management that could more frequently lead to dialysis and further transplantation. It would be interesting to identify specific risk factors of such renal toxicity. The chondroblastic sub-type may be associated with such susceptibility, but this needs to be confirmed.

X-linked hypophosphatemia and burosumab: Practical clinical points from the French experience

Hereditary hypophosphatemia with increased FGF23 levels are rare inherited metabolic diseases characterized by low serum phosphate because of impaired renal tubular phosphate reabsorption. The most common form is X-linked hypophosphatemia (XLH), secondary to a mutation in the PHEX gene. In children, XLH is often manifested by rickets, delayed development of gait, lower limb deformities, growth retardation, craniosynostosis, and spontaneous dental abscesses. In adults, patients present diffuse musculoskeletal pain (bone and joints), early osteoarthritis, entesopathies, pseudo-fractures, muscular weakness, and severe dental damage. Conventional medical management is based on the combined administration of oral phosphate supplementation with active vitamin D analogs. Treatment with the recently approved anti-FGF23 burosumab is an alternative, especially in severe forms. Burosumab restores phosphate reabsorption in the proximal tubule and stimulates the endogenous synthesis of calcitriol. In Europe, burosumab has been approved for the treatment of XLH with radiographic evidence of bone disease in pediatric patients from one year of age and in adults. This manuscript will discuss the specific management of burosumab in children and adolescents in daily practice.

The European Rare Kidney Disease Registry (ERKReg): objectives, design and initial results

BACKGROUND

The European Rare Kidney Disease Reference Network (ERKNet) recently established ERKReg, a Web-based registry for all patients with rare kidney diseases. The main objectives of this core registry are to generate epidemiological information, identify current patient cohort for clinical research, explore diagnostic and therapeutic management practices, and monitor treatment performance and patient's outcomes. The registry has a modular design that allows to integrate comprehensive disease-specific registries as extensions to the core database. The diagnosis (Orphacode) and diagnostic information (clinical, imaging, histopathological, biochemical, immunological and genetic) are recorded. Anthropometric, kidney function, and disease-specific management and outcome items informing a set of 61 key performance indicators (KPIs) are obtained annually. Data quality is ensured by automated plausibility checks upon data entry and regular offline database checks prompting queries. Centre KPI statistics and benchmarking are calculated automatically.

RESULTS

Within the first 24 months since its launch, 7607 patients were enrolled to the registry at 45 pediatric and 12 specialized adult nephrology units from 21 countries. A kidney disease diagnosis had been established in 97.1% of these patients at time of enrolment. While 199 individual disease entities were reported by Orphacode, 50% of the cohort could be classified with 11, 80% with 43 and 95% with 92 codes. Two kidney diagnoses were assigned in 6.5% of patients; 5.9% suffered from syndromic disease. Whereas glomerulopathies (54.8%) and ciliopathies including autosomal dominant polycystic kidney disease (ADPKD) (31.5%) were the predominant disease groups among adults, the pediatric disease spectrum encompassed congenital anomalies of the kidney and urinary tract (CAKUT) (33.7%), glomerulopathies (30.7%), ciliopathies (14.0%), tubulopathies (9.2%), thrombotic microangiopathies (5.6%), and metabolic nephropathies (4.1%). Genetically confirmed diagnoses were reported in 24% of all pediatric and 12% adult patients, whereas glomerulopathies had been confirmed by kidney biopsy in 80.4% adult versus 38.5% pediatric glomerulopathy cases.

CONCLUSIONS

ERKReg is a rapidly growing source of epidemiological information and patient cohorts for clinical research, and an innovative tool to monitor management quality and patient outcomes.

Pediatric atypical hemolytic-uremic syndrome due to auto-antibodies against factor H: is there an interest to combine eculizumab and mycophenolate mofetil?

BACKGROUND

Atypical hemolytic and uremic syndrome (aHUS), a thrombotic micro-angiopathy (TMA) caused by deregulation in the complement pathway, is sometimes due to the presence of anti-complement factor H (CFH) auto-antibodies. The "standard" treatment for such aHUS combines plasma exchange therapy and immunosuppressive drugs. Eculizumab, a monoclonal antibody that blocks the terminal pathway of the complement cascade, could be an interesting alternative in association with an immunosuppressive treatment for maintenance regimen.

CASE-DIAGNOSIS/TREATMENT

We report on two children, diagnosed with mildly severe aHUS due to anti-CFH antibodies, who were treated with the association eculizumab-mycophenolate mofetil (MMF). Neither side effects nor relapses were observed during the 3 years of follow-up; MMF was even progressively tapered and withdrawn successfully in one patient.

CONCLUSIONS

The association of eculizumab and MMF appears to be an effective and safe option in pediatric cases of aHUS due to anti-CFH antibodies of mild severity.

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.

Disseminated bartonellosis in a child with steroid-dependent nephrotic syndrome receiving mycophenolate mofetil monotherapy

Cat scratch disease, usually a benign infectious disease, may develop as multisystem disease with multiorgan involvement, particularly in immunocompromised patients. We report on a patient who developed disseminated bartonellosis while receiving mycophenolate mofetil monotherapy treating steroid-dependent nephrotic syndrome, highlighting that severe infection can be observed in those patients. Therefore, this category of patients should be cautious when having contact with kittens and receives proper prevention advice.

Calcium isotope fractionation by osteoblasts and osteoclasts, across endothelial and epithelial cell barriers, and with binding to proteins

Timely and accurate diagnosis of osteoporosis is essential for adequate therapy. Calcium isotope ratio (δ^44/42Ca) determination has been suggested as a sensitive, noninvasive, and radiation-free biomarker for the diagnosis of osteoporosis, reflecting bone calcium balance. The quantitative diagnostic is based on the calculation of the δ^44/42Ca difference between blood, urine, and bone. The underlying cellular processes, however, have not been studied systematically. We quantified calcium transport and δ^44/42Ca fractionation during in vitro bone formation and resorption by osteoblasts and osteoclasts and across renal proximal tubular epithelial cells (HK-2), human vein umbilical endothelial cells (HUVECs), and enterocytes (Caco-2) in transwell systems and determined transepithelial electrical resistance characteristics. δ^44/42Ca fractionation was furthermore quantified with calcium binding to albumin and collagen. Calcified matrix formed by osteoblasts was isotopically lighter than culture medium by -0.27 ± 0.03‰ within 5 days, while a consistent effect of activated osteoclasts on δ^44/42Ca could not be demonstrated. A transient increase in δ^44/42Ca in the apical compartment by 0.26‰ occured across HK-2 cells, while δ^44/42Ca fractionation was small across the HUVEC barrier and absent with Caco-2 enterocytes, and with binding of calcium to albumin and collagen. In conclusion, δ^44/42Ca fractionation follows similar universal principles as during inorganic mineral precipitation; osteoblast activity results in δ^44/42Ca fractionation. δ^44/42Ca fractionation also occurs across the proximal tubular cell barrier and needs to be considered for in vivo bone mineralization modeling. In contrast, the effect of calcium transport across endothelial and enterocyte barriers on blood δ^44/42Ca should be low and is absent with physiochemical binding of calcium to proteins.

[Interferent RNA treatment: Example of primary hyperoxaluria]

Primary hyperoxalurias are rare disease with autosomal recessive inheritance; they often lead to kidney failure and can lead to life-threatening conditions, especially in early onset forms. There are three types, responding to distinct enzyme deficits. Type 1 represents 85% of cases and results from an enzyme deficiency (alanine-glyoxylate aminotransferase) in the peroxisomes of the liver, causing hyperoxaluria leading to urolithiasis with or without nephrocalcinosis. As glomerular filtration decreases, a systemic overload appears and spares no organ. Treatment has hitherto been based on combined liver and kidney transplantation, with significant mortality and morbidity. The recent introduction of interfering RNA treatments opens up new perspectives. By blocking an enzymatic synthesis (glycolate oxidase or lacticodehydrogenase a) upstream of the deficit that causes the disease, oxaluria normalizes and the tolerance of the drug (administered by injection every 1 to 3 months) is good. This strategy will help prevent kidney failure in patients treated early and avoid liver transplantation in those who are diagnosed at an advanced stage of kidney failure.

A prospective case-control pilot study to evaluate bone microarchitecture in children and teenagers on long-term parenteral nutrition using HR-pQCT

Long-term parenteral nutrition (PN) may induce bone complications. Tridimensional bone imaging techniques such as high-resolution peripheral quantitative computed tomography (HR-pQCT) allow the assessment of both compartmental volumetric densities and microarchitecture. Our aim was to evaluate these parameters in children and teenagers receiving long-term PN. This cross-sectional, case–control study included children older than 9 years undergoing PN for at least 2 years. They were age-, gender- and puberty-matched with healthy controls (1:2). Evaluation included biological assessment of bone metabolism (serum calcium, phosphate, and albumin; urinary calcium and creatinine; 25-OH vitamin D, osteocalcin and PTH), dual X-ray absorptiometry (DXA) and HR-pQCT at the ultradistal tibia and radius. Results are presented as median [range]. Eleven patients (3 girls) with a median age of 16 [9–19] years were included. Bone parameters assessed by HR-pQCT at the ultradistal radius and tibia were similar in patients and controls. Parathyroid hormone (PTH) levels were higher (14 [7–115] vs 16 [12–27]) and osteocalcin levels were lower (44 [15–65] vs 65 [38–142]) in patients than in controls, although within the normal range. Conclusions: there were no differences for compartmental bone densities and microarchitecture in patients undergoing chronic PN. Further longitudinal studies are required to confirm these quite reassuring preliminary results.

A report from the European Hyperoxaluria Consortium (OxalEurope) Registry on a large cohort of patients with primary hyperoxaluria type 3

Outcome data in primary hyperoxaluria type 3 (PH3), described as a less severe form of the PH's with a low risk of chronic kidney disease, are scarce. To investigate this, we retrospectively analyzed the largest PH3 cohort reported so far. Of 95 patients, 74 were followed over a median of six years. Median age of first symptoms and diagnosis were 1.9 and 6.3 years, respectively. Urolithiasis was the major clinical feature observed in 70% of pediatric and 50% of adult patients. At most recent follow-up available for 56 of the 95 patients, 21.4% were in chronic kidney disease stages 2 or more. For better characterization, samples from 49 patients were analyzed in a single laboratory and compared to data from patients with PH1 and PH2 from the same center. Urinary oxalate excretion was not significantly different from PH1 and PH2 (median: 1.37, 1.40 and 1.16 mmol/1.73m²/24hours for PH1 not responsive to vitamin B6, PH2, and PH3, respectively) but was significantly higher than in vitamin B6 responsive patients with PH1. Urinary oxalate excretion did not correlate to stone production rate nor to estimated glomerular filtration rate. Normocitraturia was present even without alkalinisation treatment; hypercalciuria was found rarely. Median plasma oxalate was significantly different only to the vitamin B6-unresponsive PH1 group. Thus, PH3 is more comparable to PH1 and PH2 than so far inferred from smaller studies. It is the most favorable PH type, but not a benign entity as it constitutes an early onset, recurrent stone disease, and kidney function can be impaired.

Tyrosinemia type 1 in pediatric nephrology: Not always straightforward

The main clinical features of tyrosinemia type 1 usually appear in the first months of life, including fever, diarrhea, vomiting, liver involvement, growth failure, and renal proximal tubulopathy with subsequent hypophosphatemic rickets. An early diagnosis is crucial in order to provide specific management and to prevent complications. Here, we report on two cases referred primarily to pediatric nephrologists for the diagnosis of "neonatal tubulopathy" and management of "X-linked hypophosphatemia (XLH)," respectively. Our aim is to emphasize that (1) even a mixed tubulopathy can reveal tyrosinemia, and (2) tyrosinemia is a classic differential diagnosis of XLH that should not be forgotten, especially in the era of the anti-FGF23 burosumab.

Combined use of creatinine and cystatin C improves the detection of renal dysfunction in children undergoing home parenteral nutrition

BACKGROUND

Renal dysfunction can complicate home parenteral nutrition (HPN). The aims were, in the context of pediatric HPN, to assess renal function using the measured glomerular filtration rate (mGFR), determine the most accurate formula(s) to estimate GFR, and identify possible underlying mechanisms of renal impairment.

METHODS

A retrospective study was performed in 2 centers. Patients receiving HPN and aged 2-16 years without medical history of nephropathy were included. GFR was measured using iohexol clearance. Estimated GFR (eGFR) was calculated using creatinine, cystatin C-based, and combined (eGFR_cr+cyst ) Schwartz formulas.

RESULTS

A total of 36 patients (18 females) were included; they received HPN for 8 (2-16) years. The primary digestive disease was short-bowel syndrome for 16 (44%) patients, gastrointestinal motility disorder for 10 (28%), or congenital diarrhea for 10 (28%). The median (range) mGFR was 99 (33-136) ml/min/1.73 m² ; 9 (25%) patients had mildly decreased mGFR (<90 and ≥60 ml/min/1.73 m² ), and 2 (6%) had mildly to severely decreased mGFR (<60 ml/min/1.73 m² ). The eGFR_cr+cyst formula was the most accurate and precise to estimate GFR. A significant negative correlation between mGFR and PN duration was found for patients receiving PN for 6-7/7 days (P = .008). Activation of the renin-angiotensin system was identified in 15 of 36 (42%) patients.

CONCLUSION

Renal dysfunction was frequent and correlated with the duration of PN only for patients with the most severe intestinal failure. The use of eGFR_cr+cyst improves its detection in these patients. Chronic dehydration may be an underlying mechanism.

Adherence to cysteamine in nephropathic cystinosis: A unique electronic monitoring experience for a better understanding. A prospective cohort study: CrYSTobs

INTRODUCTION

In nephropathic cystinosis (NC), adherence to cysteamine remains challenging; poor adherence is worsening the disease progression with a decline of kidney function and increase of extrarenal morbidities. Our objective was to describe adherence to cysteamine in NC patients, using electronic monitoring systems.

METHODS

Patients with confirmed NC, aged > 4 years and receiving oral cysteamine (short acting or delayed release formulation as standard of care) from 3 French reference centers, were included. Adherence to treatment was primarily assessed as the percentage of days with a good adherence score, adherence score rating from 0 (poor) to 2 (good). A descriptive analysis was performed after 1-year follow-up.

RESULTS

Seventeen patients (10 girls, median age: 13.9 (5.4-33.0) years) were included. Median age at diagnosis was 17.0 (3.0-76.9) months and age at start of cysteamine was 21.0 (15.5-116.3) months. Median daily dose of cysteamine was 1.05 (0.55-1.63) g/m²/day. Over the year, the median percentage of days with a good adherence score was 80 (1-99)% decreasing to 68 (1-99)% in patients > 11 years old. The median of average number of hours covered by treatment in a day was 22.5 (6.1-23.9) versus 14.9 (9.2-20.5) hours for delayed release versus short acting cysteamine.

CONCLUSION

Our data are the first describing a rather good adherence to cysteamine, decreasing in adolescents and adults. We described a potential interest of the delayed release formulation. Our data highlight the need for a multidisciplinary approach including therapeutic education and individualized approaches in NC patients transitioning to adulthood. Graphical abstract.

Review: Neonatal dialysis is technically feasible but ethical and global issues need to be addressed

AIM

Our aim was to look at the technical, ethical and global issues related to neonatal dialysis.

METHODS

We performed a PubMed research on manuscripts published from March 2010 to March 2020 and retrospectively reviewed all neonates who received dialysis in our French paediatric and neonatal intensive care units from April 2009 to March 2019.

RESULTS

Dialysis is performed on neonates with pre-existing renal diseases, acute kidney injuries or inborn errors of metabolism. It is required in 0.5%-1% of neonates admitted to the neonatal intensive care units. Peritoneal dialysis and extracorporeal blood purification are both feasible, with more complications, but the results are close to those obtained in older infants, at least in children without multi-organ dysfunction. Novel haemodialysis machines are being evaluated. Ethical issues are a major concern. Multidisciplinary teams should consider associated comorbidities, risks of permanent end-stage renal disease and provide parents with full and neutral information. These should drive decisions about whether dialysis is in child's best interests.

CONCLUSION

Neonatal dialysis is technically feasible, but ethically challenging, and short-term and long-term data remain limited. Prospective studies and dialysis registries would improve global management and quality of life of these patients at risk of chronic kidney disease.

Bone evaluation in paediatric chronic kidney disease: clinical practice points from the European Society for Paediatric Nephrology CKD-MBD and Dialysis working groups and CKD-MBD working group of the ERA-EDTA

Mineral and bone disorder (MBD) is widely prevalent in children with chronic kidney disease (CKD) and is associated with significant morbidity. CKD may cause disturbances in bone remodelling/modelling, which are more pronounced in the growing skeleton, manifesting as short stature, bone pain and deformities, fractures, slipped epiphyses and ectopic calcifications. Although assessment of bone health is a key element in the clinical care of children with CKD, it remains a major challenge for physicians. On the one hand, bone biopsy with histomorphometry is the gold standard for assessing bone health, but it is expensive, invasive and requires expertise in the interpretation of bone histology. On the other hand, currently available non-invasive measures, including dual-energy X-ray absorptiometry and biomarkers of bone formation/resorption, are affected by growth and pubertal status and have limited sensitivity and specificity in predicting changes in bone turnover and mineralization. In the absence of high-quality evidence, there are wide variations in clinical practice in the diagnosis and management of CKD-MBD in childhood. We present clinical practice points (CPPs) on the assessment of bone disease in children with CKD Stages 2-5 and on dialysis based on the best available evidence and consensus of experts from the CKD-MBD and Dialysis working groups of the European Society for Paediatric Nephrology and the CKD-MBD working group of the European Renal Association-European Dialysis and Transplant Association. These CPPs should be carefully considered by treating physicians and adapted to individual patients' needs as appropriate. Further areas for research are suggested.

Presenting features and molecular genetics of primary hyperparathyroidism in the paediatric population

AIM

To describe the presenting features and molecular genetics of primary hyperparathyroidism (PHPT) in the paediatric population.

METHODS

Retrospective study of 63 children diagnosed with primary PHPT from 1998 to 2018.

RESULTS

Compared to older children, infants were often asymptomatic (54% vs 15%, P = 0.002) with a milder form of PHPT. When symptomatic, children and adolescents mostly presented with non-specific complaints such as asthenia, depression, weight loss, vomiting or abdominal pain. A genetic cause of PHPT was identified in about half of this cohort (52%). The infancy period was almost exclusively associated with mutation in genes involved in the calcium-sensing receptor (CaSR) signalling pathway (i.e. CaSR and AP2S1 genes, 'CaSR group'; 94% of infants with mutations) whereas childhood and adolescence were associated with mutation in genes involved in parathyroid cell proliferation (i.e. MEN1, CDC73, CDKN1B and RET genes, 'cell proliferation group'; 69% of children and adolescents with mutations). Although serum calcium levels did not differ between the two groups (P = 0.785), serum PTH levels and the urinary calcium/creatinine ratio were significantly higher in 'cell proliferation group' patients compared to those in the 'CaSR group' (P = 0.001 and 0.028, respectively).

CONCLUSION

Although far less common than in adults, PHPT can develop in children and is associated with significant morbidity. Consequently, this diagnosis should be considered in children with non-specific complaints and lead to monitoring of mineral homeostasis parameters. A genetic cause of PHPT can be identified in about half of these patients.

Intermittent Bi-Daily Sub-cutaneous Teriparatide Administration in Children With Hypoparathyroidism: A Single-Center Experience

Introduction: The use of teriparatide has been reported in children with hypoparathyroidism as an investigational physiologic replacement therapy. Methods: We aimed to retrospectively report our pediatric experience of bi-daily sub-cutaneous teriparatide. Results are presented as median (25th-75th quartile). As part of the routine follow-up of these patients with hypoparathyroidism, total calcium at H0 (i.e., just before injection) and H4 (i.e., 4 h after teriparatide injection) and other biomarker parameters were regularly assessed. Results: At a median age of 10.7 (8.1-12.6) years, an estimated glomerular filtration rate (eGFR) of 110 (95-118) mL/min/1.73 m², calcium levels of 1.87 (1.81-1.96) mmol/L and an age-standardized phosphate of 3.8 (2.5-4.9) SDS, teriparatide therapy was introduced in 10 patients at the dose of 1.1 (0.7-1.5) μg/kg/day (20 μg twice daily), with further adjustment depending on calcium levels. Six patients already displayed nephrocalcinosis. Severe side effects were reported in one child: two episodes of symptomatic hypocalcemia and one of iatrogenic hypercalcemia; one teenager displayed dysgueusia. Calcium levels at H0 did not significantly increase whilst calcium at H4 and phosphate levels significantly increased and decreased, respectively. After 12 months, eGFR, calcium and age-standardized phosphate levels were 108 (90-122) mL/min/1.73 m², 2.36 (2.23-2.48) mmol/L, 0.5 (-0.1 to 1.5), and 68 (63-74) nmol/L, respectively, with a significant decrease in phosphate levels (p = 0.01). Urinary calcium and calcium/creatinine ratio remained stable; no nephrolithiasis was observed but two moderate nephrocalcinosis appeared. Conclusion: Intermittent teriparatide therapy significantly improves calcium and phosphate control, without increasing calciuria. It appears to be safe and well-tolerated in children.

Overlapping Phenotypes Associated With CYP24A1, SLC34A1, and SLC34A3 Mutations: A Cohort Study of Patients With Hypersensitivity to Vitamin D

Mutations in CYP24A1 (vitamin D 24-hydroxylase) and SLC34A1 (renal phosphate transporter NPT2a) cause autosomal recessive Infantile Hypercalcemia type 1 and 2, illustrating links between vitamin D and phosphate metabolism. Patients may present with hypercalciuria and alternate between chronic phases with normal serum calcium but inappropriately high 1,25-(OH)₂D and appropriately low PTH, and acute phases with hypercalcemia with suppressed PTH. Mutations in SLC34A3 and SLC9A3R1 have been associated with phosphate wasting without hypercalcemia. The aims of this study were to evaluate the frequency of mutations in these genes in patients with a medical history suggestive of CYP24A1 mutation to search for a specific pattern. Using next generation sequencing, we screened for mutations in 185 patients with PTH levels < 20 pg/mL, hypercalcemia and/or hypercalciuria, and relatives. Twenty-eight (15%) patients harbored biallelic mutations in CYP24A1 (25) and SLC34A3 (3), mostly associated with renal disease (lithiasis, nephrocalcinosis) (86%). Hypophosphatemia was found in 7 patients with biallelic mutations in CYP24A1 and a normal phosphatemia was reported in 2 patients with biallelic mutations in SLC34A3. Rare variations in SLC34A1 and SLC34A3 were mostly of uncertain significance. Fifteen patients (8%) carried only one heterozygous mutation. Heterozygous relatives carrying SLC34A1 or SLC34A3 variation may present with biochemical changes in mineral metabolism. Two patients' genotype may suggest digenism (heterozygous variations in different genes). No variation was found in SLC9A3R1. As no specific pattern can be found, patients with medical history suggestive of CYP24A1 mutation should benefit from SLC34A1 and SLC34A3 analysis.

Hyperphosphatemia and Chronic Kidney Disease: A Major Daily Concern Both in Adults and in Children

Hyperphosphatemia is common in chronic kidney disease (CKD). Often seen as the "silent killer" because of its dramatic effect on vascular calcifications, hyperphosphatemia explains, at least partly, the onset of the complex mineral and bone disorders associated with CKD (CKD-MBD), together with hypocalcemia and decreased 1-25(OH)₂ vitamin D levels. The impact of CKD-MBD may be immediate with abnormalities of bone and mineral metabolism with secondary hyperparathyroidism and increased FGF23 levels, or delayed with poor growth, bone deformities, fractures, and vascular calcifications, leading to increased morbidity and mortality. The global management of CKD-MBD has been detailed in international guidelines for adults and children, however, with difficulties to obtain an agreement on the ideal PTH targets. The clinical management of hyperphosphatemia is a daily challenge for nephrologists and pediatric nephrologists, notably because of the phosphate overload in occidental diets that is mainly due to the phosphate "hidden" in food additives. The management begins with a dietary restriction of phosphate intake, and is followed by the use of calcium-based and non-calcium-based phosphate binders, and/or the intensification of dialysis. The objective of this review is to provide an overview of the pathophysiology of hyperphosphatemia in CKD, with a focus on its deleterious effects and a description of the clinical management of hyperphosphatemia in a more global setting of CKD-MBD.

Hypertension in Children and Adolescents: A Position Statement From a Panel of Multidisciplinary Experts Coordinated by the French Society of Hypertension

Hypertension is much less common in children than in adults. The group of experts decided to perform a review of the literature to draw up a position statement that could be used in everyday practice. The group rated recommendations using the GRADE approach. All children over the age of 3 years should have their blood pressure measured annually. Due to the lack of data on cardiovascular morbidity and mortality associated with blood pressure values, the definition of hypertension in children is a statistical value based on the normal distribution of blood pressure in the paediatric population, and children and adolescents are considered as having hypertension when their blood pressure is greater than or equal to the 95th percentile. Nevertheless, it is recommended to use normative blood pressure tables developed according to age, height and gender, to define hypertension. Measuring blood pressure in children can be technically challenging and several measurement methods are listed here. Regardless of the age of the child, it is recommended to carefully check for a secondary cause of hypertension as in 2/3 of cases it has a renal or cardiac origin. The care pathway and principles of the therapeutic strategy are described here.