Renal function and histology in children after small bowel transplantation.

CKD is a frequent long-term complication after SBTx. CNIs are a well-known factor, but probably not the only cause. We assessed the incidence, risk factors, and severity of CKD in 27 children with SBTx (15 combined liver/SBTx) and prednisone/TAC-based maintenance immunosuppression. Median follow-up was seven yr (3-21). A renal biopsy was performed in 14 patients, 1-18 yr post-SBTx. A reduced GFR was observed in 17 children (63%) during the follow-up with none requiring dialysis. CNI toxicity was observed in 11/14 biopsies, as early as two yr post-transplant, and could occur with a normal mGFR. The dose of TAC was reduced by 50% in 13 patients with CKD and/or significant kidney histological lesions, and six were also given MMF. This led to a significant improvement in renal function: mGFR normalized in eight patients and improved or stabilized in five. No rejection occurred. At last follow-up, 37% had CKD stage 2 and 15% had CKD stage 3. In conclusion, CKD is frequent in children after SBTx and probably multifactorial. Less nephrotoxic immunosuppressive protocols may improve mGFR and should be further considered. The kidney histology helps in designing personalized immunosuppression strategies for patients.

Band 3 Courcouronnes (Ser667Phe): a trafficking mutant differentially rescued by wild-type band 3 and glycophorin A.

We describe a mutation in human erythrocyte band 3 (anion exchanger 1; SLC4A1) causing both hereditary spherocytosis and distal renal tubular acidosis. The proband developed a transfusion-dependent, hemolytic anemia following birth. Immunoblotting showed band 3 was reduced to approximately 35% of wildtype; other proteins of the band 3/Rh macrocomplex were also reduced. DNA sequence analysis revealed a novel homozygous mutation, c.2000C>T, leading to the amino acid substitution Ser667Phe. The parents were heterozygous for the same mutation. Sulfate influx in the patient's erythrocytes was approximately 40% wild type. The mutant band 3 produced very little chloride influx when expressed in Xenopus oocytes. Influx was partially rescued by coexpression of glycophorin A and also rescued by coexpression of wild-type band 3. At 2 years of age, an ammonium chloride challenge showed the child has incomplete distal renal tubular acidosis (dRTA). Stable expression of mutant kidney band 3 in both nonpolarized and polarized Madin-Darby canine kidney cells showed that most of the mutant protein was retained in the endoplasmic reticulum. Overall our results suggest that the Ser667Phe does not affect the anion transport function of band 3, but causes a trafficking defect in both erythrocytes and kidney cells.

Clinical variability of familial tumoral calcinosis caused by novel GALNT3 mutations.

The GALNT3 gene encodes GalNAc-T3, which prevents degradation of the phosphaturic hormone, fibroblast growth factor 23 (FGF23). Biallelic mutations in either GALNT3 or FGF23 result in hyperphosphatemic familial tumoral calcinosis or its variant, hyperostosis-hyperphosphatemia syndrome. Tumoral calcinosis is characterized by the presence of ectopic calcifications around major joints, whereas hyperostosis-hyperphosphatemia syndrome is characterized by recurrent long bone lesions with hyperostosis. Here we investigated four patients with hyperphosphatemia and clinical manifestations including tumoral calcinosis and/or hyperostosis-hyperphosphatemia syndrome to determine underlying genetic cause and delineate phenotypic heterogeneity of these disorders. Mutational analysis of FGF23 and GALNT3 in these patients revealed novel homozygous mutations in GALNT3. Although the presence of massive calcifications, cortical hyperostosis, or dental anomalies was not shared by all patients, all had persistent hyperphosphatemia. Three of the patients also had inappropriately normal 1,25-dihyroxyvitamin D [1,25(OH)(2)D] and confirmed low circulating intact FGF23 concentrations. The four novel GALNT3 mutations invariably resulted in hyperphosphatemia as a result of low intact FGF23, but other clinical manifestations were variable. Therefore, tumoral calcinosis and hyperostosis-hyperphosphatemia syndrome represent a continuous spectrum of the same disease caused by increased phosphate levels, rather than two distinct disorders.

Vitamin D receptor genotype in hypophosphatemic rickets as a predictor of growth and response to treatment.

CONTEXT: Treatment of X-linked hypophosphatemic rickets improves bone mineralization and bone deformities, but its effect on skeletal growth is highly variable. OBJECTIVE: Genetic variants in the promoter region of the vitamin D receptor (VDR) gene may explain the response to treatment because this receptor mediates vitamin D action. DESIGN: We studied the VDR promoter haplotype structure in a large cohort of 91 patients with hypophosphatemic rickets including 62 patients receiving 1alpha-hydroxyvitamin D3 derivatives and phosphates from early childhood on. RESULTS: Treatment improved bone deformities and final height, but 39% of treated patients still had short stature at the end of growth (-2 sd score or below). Height was closely associated with VDR promoter Hap1 genotype. Hap1(-) patients (35% of the cohort) had severe growth defects. This disadvantageous association of Hap1(-) status with height was visible before treatment, under treatment, and on to adulthood. Gender and age at initiation of treatment could not account for the Hap1 effect. No association with growth was found with a polymorphism of the PTH receptor gene otherwise found to be associated with adult height. Compared with Hap1(+) patients, those who were Hap1(-) had a higher urinary calcium response to 1alpha-hydroxyvitamin D3 and had significantly lower circulating FGF23 levels (C-terminal assay), taking into account their phosphate and 1alpha-hydroxyvitamin D3 intakes. CONCLUSIONS: The present work identifies the VDR promoter genotype as a key predictor of growth under treatment with 1alpha-hydroxyvitamin D3 derivatives in patients with hypophosphatemic rickets, including those with established PHEX alterations. The VDR promoter genotype appears to provide valuable information for adjusting treatment and for deciding upon the utility of early GH therapy.

Increased beta-2 microglobulinuria in human immunodeficiency virus-1-infected children and adolescents treated with tenofovir.

A single-center cross sectional evaluation of beta-2 micro-globinuria as a marker of proximal renal tubule damage in 92 HIV-infected children showed that tenofovir treatment was significantly associated with very high abnormal values. In view of the very long duration of treatments for HIV infection, their possible consequences for the child's growing body should be carefully evaluated.

Dietary salt restriction accelerates atherosclerosis in apolipoprotein E-deficient mice.

BACKGROUND: Whether a general reduction in salt intake reduces or actually enhances cardiovascular mortality in man remains an issue of controversy. Low sodium diets may lead to adverse side effects by stimulating the renin-angiotensin and sympathetic nervous systems. The present study was designed to investigate the effects of low dietary salt on atherosclerotic lesion progression in apolipoprotein E deficient (apoE(-/-)) mice. METHODS AND RESULTS: We fed 7-week-old apoE(-/-) mice on low (0.036% NaCl; n=28) or regular (0.64% NaCl; n=26) salt diets for 16 weeks. At the age of 23 weeks, the cross-section surface area of atherosclerotic plaques was measured in aortic root and thoracic aorta. Serum total cholesterol, triglycerides, plasma angiotensin levels and urinary protein/creatinine concentrations were assessed. Exposure to low salt caused significant increases in atherosclerotic lesion surface area in thoracic aorta, but did not alter lesion area in aortic root. Low-salt mice also had higher serum total cholesterol and higher plasma angiotensin II (ANG-II) concentrations. Atherosclerotic lesion area was correlated with ANG-II levels in low-salt but not in regular-salt animals, and with total cholesterol concentration in all mice. Mean arterial pressure was comparable in both groups. CONCLUSIONS: Dietary salt restriction accelerated atherosclerotic lesion formation in apoE(-/-) mice through a mechanism that is probably related to ANG-II formation. Whether these findings are relevant to human cardiovascular disease remains to be evaluated.

Improvement of renal function in pediatric heart transplant recipients treated with low-dose calcineurin inhibitor and mycophenolate mofetil.

BACKGROUND: Renal dysfunction is a major complication in heart transplant recipients treated with calcineurin inhibitors. The goal of the study was to investigate the effect of a reduction of calcineurin inhibitor dosage with the concomitant introduction of mycophenolate mofetil on both renal function and cardiac allograft function. METHODS: Fourteen of 52 consecutive pediatric cardiac allograft recipients experienced a progressive decrease of renal function. A renal biopsy was performed before the dose of calcineurin inhibitors was reduced by 50% and azathioprine was replaced by mycophenolate mofetil. Renal function was evaluated by inulin clearance and maximal urinary osmolality before and yearly after the therapeutic changes. Acute rejection was monitored clinically, by echocardiography and endomyocardial biopsies. RESULTS: Inulin clearance in the fourteen children decreased from 84.2 mL/min/1.73 m at one year posttransplantation to 46.5+/-9.6 mL/min/1.73 m at the time of the change in immunosuppressive therapy. Significant renal lesions were observed in the renal biopsies performed before the change. At 1 year, inulin clearance had increased by 67%. In six patients who had a second determination 2 years after the switch, inulin clearance was not significantly different from the value at 1 year. There were three reversible acute rejection episodes in three patients. The incidence of rejection episodes was not different from a control group of patients whose treatment was not changed. CONCLUSION: The reduction of calcineurin inhibitor dosage and replacement of azathioprine by mycophenolate mofetil is a safe way to improve renal function in children with heart transplants and calcineurin inhibitor induced nephrotoxicity.

Basic protocol for transepithelial nasal potential difference measurements.

Transepithelial nasal potential difference (NPD) measurements assess ion conductance in the upper respiratory epithelium. NPD is useful in assisting in the diagnosis of classical and atypical cystic fibrosis (CF) and of cystic fibrosis transmembrane regulator (CFTR)-related disorders, as well as for monitoring the effect of pharmacological agents and gene transfer approaches to correct the abnormalities of ion transport in CF. The article summarizes the objectives and the principle of NPD measurements, describes a hands-on protocol of the procedure and provides quality control measures, practical hints and troubleshooting.

Transient hyper-17-hydroxyprogesteronemia: a clinical subgroup of patients diagnosed at neonatal screening for congenital adrenal hyperplasia.

OBJECTIVE: Neonatal screening for congenital adrenal hyperplasia (CAH) is characterized by a high false-positive rate, mainly among preterm and low birth weight infants. The aims of this study were to describe a subgroup of infants with transient serum hyper-17-hydroxyprogesteronemia (hyper-17-OHPemia) and to compare them with false positive and affected by 21-hydroxylase deficiency newborns. METHODS: We retrospectively analyzed the clinical data of all newborns positive at CAH neonatal screening, who were referred to our hospital to confirm the diagnosis from 2002 to 2006. They were submitted to clinical investigations and blood tests to evaluate 17-hydroxyprogesterone (17-OHP), renin, and electrolyte levels. CAH-unaffected newborns with increased serum 17-OHP were submitted to strict follow-up monitoring, which included an ACTH-stimulating test and genetic analysis of the 21-hydroxylase gene, until serum 17-OHP decreased. RESULTS: Thirty-seven newborns with gestational ages ranging from 33 to 40 weeks were studied. Eight infants (three male and five female) were affected by CAH (serum 17-OHP: 277.5 (210-921) nmol/l), 14 (ten male and four female) were false positives (17-OHP: 3.75 (0.3-8.4) nmol/l), and 15 (ten male and five female) showed a serum hyper-17-OHPemia (17-OHP: 15.9 (9.9-33) nmol/l). No mutations of the 21-hydroxylase gene were found in infants with hyper-17-OHPemia and their serum 17-OHP levels were normalized by the third month of life. CONCLUSION: We identified a population of infants with transient serum hyper-17-OHPemia, and no clinical signs of disease or 21-hydroxylase gene mutations. No further investigations are necessary after birth in these newborns if 17-OHP levels decrease, other confirmatory tests such as ACTH-stimulation test or genotyping analysis are necessary only if symptoms appear.

Cyclosporin therapy in patients with Alport syndrome.

Alport syndrome (AS) is a hereditary disorder of type IV collagen characterized by the association of progressive hematuric nephritis and sensorineural hearing loss. An increase in proteinuria is linked with progressive renal failure. Preliminary data have shown that cyclosporin therapy reduces proteinuria, thereby suggesting that it may also slow the progression of AS nephropathy. We treated nine AS patients manifesting proteinuria >1 g/m(2)/day and a glomerular filtration rate (GFR) >50 ml/min/1.73 m(2) with cyclosporin for at least 6 months. At the end of this 6-month period, mean proteinuria had decreased from 2+/-1.06 to 0.65+/-0.73 g/day, and mean albuminemia had increased from 29+/-5.2 to 35+/-6.5 g/l. Mean inulin clearance had decreased from 102+/-29 to 74+/-16.3 ml/min/1.73 m(2). Cyclosporin treatment was stopped in four patients because of inefficacy or adverse effects and continued in the remaining five patients for an additional 14-42 months. At the end of this second treatment period, control renal biopsies revealed significant lesions of cyclosporin nephrotoxicity in three patients. Based on these results we conclude that while cyclosporin therapy can decrease proteinuria in most patients with AS, it may be associated with nephrotoxicity, thereby precluding its long-term use.

Congenital disorders of glycosylation type I: a rare but new cause of hyperechoic kidneys in infants and children due to early microcystic changes.

BACKGROUND: There are numerous causes of bilateral hyperechoic kidneys. Congenital disorders of glycosylation (CDGs) are a rapidly growing family of inherited disorders due to defects in the synthesis of the glycans of glycoproteins or other glycoconjugates. OBJECTIVE: To describe renal sonographic abnormalities in CDG type I in infants and children. MATERIAL AND METHODS: A retrospective study of renal US in 12 infants and children: 8 CDG-Ia (6 multivisceral forms, 2 neurological forms), 2 CDG-Ib, and 2 CDG-Ix, with detailed functional renal tests in 6. Histology of the kidneys of one 35-week fetus with CDG-Ia was available. RESULTS: Renal US was normal in the two children with the neurological form of CDG-Ia. All patients with the multivisceral form of CDG-Ia or with CDG-Ib showed increased cortical echogenicity, and/or abnormal pyramids (small +/- hyperechoic). The two patients with CDG-Ix showed predominant involvement of the medulla, with inverted corticomedullary differentiation in one. Kidney size was normal in all but two patients. The fetal kidneys exhibited diffuse microcysts arising from the distal tubules. CONCLUSIONS: Hyperechoic kidneys are common in CDG-I patients, contrasting with grossly preserved renal function. The US pattern seems to differ slightly according to the type of CDG-I, and is consistent with microcystic changes of the renal parenchyma, which occur prenatally, and may be due to ciliary dysfunction secondary to altered glycosylation of tubular glycoproteins. CDG-I, which remains largely underdiagnosed at present, should be added to the causes of hyperechoic kidneys in children, especially in cases of multivisceral involvement, after ruling out other more frequent causes.

Genetic investigation of autosomal recessive distal renal tubular acidosis: evidence for early sensorineural hearing loss associated with mutations in the ATP6V0A4 gene.

Mutations in the ATP6V1B1 and ATP6V0A4 genes, encoding subunits B1 and 4 of apical H(+) ATPase, cause recessive forms of distal renal tubular acidosis (dRTA). ATP6V1B mutations have been associated with early sensorineural hearing loss (SNHL), whereas ATP6V0A4 mutations are classically associated with either late-onset SNHL or normal hearing. The phenotype and genotype of 39 new kindreds with recessive dRTA, 18 of whom were consanguineous, were assessed. Novel and known loss-of-function mutations were identified in 31 kindreds. Fourteen new and five recurrent mutations of the ATP6V0A4 gene were identified in 21 families. For the ATP6V1B1 gene, two new and two previously described mutations were identified in 10 families. Surprisingly, seven probands with ATP6V0A4 gene mutations developed severe early SNHL between the ages of 2 mo and 10 yr. No mutation was detected in eight families. These data extend the spectrum of disease-causing mutations and provide evidence for genetic heterogeneity in SNHL. The data also demonstrate that mutations in either of these genes may cause early deafness, and they highlight the importance of genetic screening for recessive forms of dRTA independent of hearing status.

Chloride transport in nasal ciliated cells of cystic fibrosis heterozygotes.

Studying subjects heterozygous for mutations of the cystic fibrosis (CF) gene may help clarify the impact on disease onset of CF transmembrane conductance regulator protein (CFTR-)-dependent chloride secretion. CFTR-mediated chloride transport was evaluated in 52 heterozygous subjects, 32 healthy control subjects, and 77 patients with CF with class I or II mutations. We measured the change in nasal potential difference in response to chloride-free isoproterenol solution for each subject and used a video-imaging fluorescent dye assay to assess the percentage of nasal ciliated cells with cAMP-dependent anion conductance. Our findings did not confirm the standard assumption that heterozygosity implies 50% of normal CFTR function. Half the heterozygous subjects had CFTR-mediated chloride transport levels below 50% of the normal range, and one-third had levels similar to those of the patients with CF. This reduced CFTR function was not associated with an elevated prevalence of CF-like symptoms in heterozygous subjects but was highly related to respiratory status in the patients with CF. These data suggest that CFTR-dependent chloride conductance does not directly modulate disease severity but may be part of a more global defect in patients with CF involving other CFTR functions or currently unknown modulatory factors.

Sildenafil inhibits altitude-induced hypoxemia and pulmonary hypertension.

Exposure to high altitude induces pulmonary hypertension that may lead to life-threatening conditions. In a randomized, double-blind, placebo-controlled study, the effects of oral sildenafil on altitude-induced pulmonary hypertension and gas exchange in normal subjects were examined. Twelve subjects (sildenafil [SIL] n = 6; placebo [PLA] n = 6) were exposed for 6 days at 4,350 m. Treatment (3 x 40 mg/day) was started 6 to 8 hours after arrival from sea level to high altitude and maintained for 6 days. Systolic pulmonary artery pressure (echocardiography) increased at high altitude before treatment (+29% versus sea level, p < 0.01), then normalized in SIL (-6% versus sea level, NS) and remained elevated in PLA (+21% versus sea level, p < 0.05). Pulmonary acceleration time decreased by 27% in PLA versus 6% in SIL (p < 0.01). Cardiac output and systemic blood pressures increased at high altitude then decreased similarly in both groups. Pa(O(2)) was higher and alveolar-arterial difference in O(2) lower in SIL than in PLA at rest and exercise (p < 0.05). The altitude-induced decrease in maximal O(2) consumption was smaller in SIL than in PLA (p < 0.05). Sildenafil protects against the development of altitude-induced pulmonary hypertension and improves gas exchange, limiting the altitude-induced hypoxemia and decrease in exercise performance.

Recovery of plasma volume after 1 week of exposure at 4,350 m.

Plasma volume (PV) decreases at high altitude, but is rapidly restored upon return to sea-level (RSL). The aim of this study was (1) to describe PV recovery upon RSL with concomitant changes in major fluid regulating hormones, and (2) to test the hypothesis that PV recovery is promoted by the administration of a plasma expander. Ten male subjects were evaluated at rest and during submaximal exercise at sea-level (SL), after 7 days at 4,350 m (H7), and on RSL, on day 1 (RSL1, rest only) and day 2 (RSL2). PV (measured by carbon monoxide rebreathing), plasma renin (Ren), aldosterone (Aldo), atrial natriuretic factor (ANF) and arginine vasopressin (AVP) were measured at rest and during exercise. The subjects were divided into two groups 1 h before RSL, one group receiving PV expansion (475+/-219 ml) to ensure normovolemia (PVX, n=6), the others serving as controls (Control, n=4). PV decreased by 13.6% in H7 ( n=10), but was restored in RSL2, regardless of PVX. Ren, Aldo and AVP, which were similar in both groups, were reduced in H7, but were higher in RSL2 (rest or exercise). ANF was modified neither by hypoxia nor by PVX. Total water intake was reduced in H7, but remained normal in RSL in both groups, whereas water output dropped in RSL. PVX increased urine flow rate in RSL1 compared with subjects not given PVX. The present results suggest that PV recovery during early RSL is mainly due to a decreased diuresis, promoted at least in part by changes in fluid regulating hormones. However, neither PV recovery, nor hormonal responses were altered with PVX-induced normovolemia upon RSL.

Functional characterization of a calcium-sensing receptor mutation in severe autosomal dominant hypocalcemia with a Bartter-like syndrome.

The extracellular Ca(2+)-sensing receptor (CaSR) plays an essential role in extracellular Ca(2+) homeostasis by regulating the rate of parathyroid hormone (PTH) secretion and the rate of calcium reabsorption by the kidney. Activation of the renal CaSR is thought to inhibit paracellular divalent cation reabsorption in the cortical ascending limb (cTAL) both directly and indirectly via a decrease in NaCl transport. However, in patients with autosomal dominant hypocalcemia (ADH), caused by CaSR gain-of-function mutations, a defect in tubular NaCl reabsorption with renal loss of NaCl has not been described so far. This article describes a patient with ADH due to a gain-of-function mutation in the CaSR, L125P, associated with a Bartter-like syndrome that is characterized by a decrease in distal tubular fractional chloride reabsorption rate and negative NaCl balance with secondary hyperaldosteronism and hypokalemia. The kinetics of activation of the L125P mutant receptor expressed in HEK-293 cells, assessed by measuring CaSR-stimulated changes in intracellular Ca(2+) and ERK activity, showed a dramatic reduction in the EC(50) for extracellular Ca(2+) compared with the wild-type and a loss-of-function mutant CaSR (I40F). This study describes the first case of ADH associated with a Bartter-like syndrome. It is herein proposed that the L125P mutation of the CaSR, which represents the most potent gain-of-function mutation reported so far, may reduce NaCl reabsorption in the cTAL sufficiently to result in renal loss of NaCl with secondary hyperaldosteronism and hypokalemia.