Primary hyperoxaluria type 1: practical and ethical issues

Primary hyperoxaluria type 1 (PH1) is a rare inborn error of glyoxylate metabolism of autosomal recessive inheritance, leading to progressive systemic oxalate storage (named 'oxalosis') with a high rate of morbidity and mortality, as well as an unacceptable quality of life for most patients. The adverse outcome, however, is partly due to issues that can be overcome. First, the diagnosis of PH is often delayed due to a general lack of knowledge of the disease among physicians. This accounts specifically for patients with pyridoxine sensitive PH, a group that is paradoxically most easy to treat. Second, lack of adherence to a strict conduction of conservative treatment and optimal urological management may enhance an adverse outcome of the disease. Third, specific techniques to establish PH1 and specific therapies are currently often not available in several low-resources countries with a high prevalence of PH. The management of patients with advanced disease is extremely difficult and warrants a tailor-made approach in most cases. Comprehensive programs for education of local physicians, installation of national centers of expertise, European support of low-resources countries for the management of PH patients and intensified international collaboration on the management of current patients, as well as on conduction of clinical studies, may further improve outcome of PH.

Takayasu arteritis in children

Takayasu arteritis (TA) is a large vessel vasculitis that usually affects young female patients during the second and third decades of life, but has been reported in children as young as 24 months of age. Aim of this report was to describe four children (two girls) with TA, as well as summarizing main published studies. The mean age at presentation of our cases was 11 years (range 8-15). Three patients were Caucasians and one Asian. Arterial hypertension was the commonest mode of presentation followed by systemic symptoms. Other related symptoms were due to ischemia and consisted of abdomen, chest, and limb pain. An abdominal bruit was noted in only one patient. Inflammation markers were always abnormal. Angiography was performed in all cases; left subclavian artery and common carotid artery were more frequently involved. Renal artery stenosis was observed in two patients. One boy was diagnosed as having an associated immune deficiency (Wiskott-Aldrich syndrome). Treatment modalities included prednisone (n = 4), methotrexate (n = 3), and mycophenolate mofetil (MMF) (n = 1). Surgery was required in two patients. Follow-up ranged from 3 to 10 years since diagnosis. In three cases antihypertensive drugs and methotrexate were stopped, and prednisone was reduced to 7.5 mg/day.

Characterization of a putative founder mutation that accounts for the high incidence of cystinosis in Brittany

Cystinosis is an autosomal recessive disorder, characterized by an accumulation of intralysosomal cystine, with an incidence of 1 in 100,000 to 200,000 live births. A higher incidence of cystinosis, 1 in 26,000 live births, has been reported in the western French province of Brittany. PCR amplification and sequencing has identified a 27-bp deletion starting 3 bp before the end of exon 8 and continuing into intron 8, 898-900+24del27, which has only been detected in families from this region. Reverse transcription-PCR amplification of RNA from an affected individual has shown that this mutation is indeed a splice-site mutation and results in the production of aberrant transcripts. These transcripts are predicted to either severely truncate cystinosin or alter its topology, thus accounting for the severe phenotype of these individuals. The mutation 898-900+24del27 has been identified in 7 of 18 alleles studied. This mutation is likely to be a founder mutation and would account for the higher incidence of cystinosis in Brittany.(1)

Body composition in children with renal disease: use of dual energy X-ray absorptiometry

Dual energy X-ray absorptiometry (DEXA) is a non-invasive accurate method which estimates bone mineral content and density (BMD), as well as fat (FM) and lean (LM) body mass. This method was used in control children in order to establish normal values for BMD of lumbar spine and whole body composition ¿logistic curves, general equation E = k+K/[1+ alpha exp(- beta A)]¿. In children with chronic renal failure (CRF), LM correlated with the urinary excretion of creatinine (r = 0.97, P = 0.0001) independently from glomerular filtration rate. However, the assessment of LM by DEXA must take into account the hydration level, since there is a positive correlation between fluid loss and reduction in LM in children on hemodialysis (r = 0.98, P = 0.0001). After renal transplantation, a significant loss of BMD (median -9.2%) was observed at 6 months which returned to 95% of pretransplant values by the end of the 1st year. Maximal changes in LM and FM occurred during the first 3 months (-7.8% and +7.2%, respectively) and may be due to steroids; these should be influenced by physical activity since FM correlated inversely with maximal oxygen consumption (r = 0.69, P = 0.0001). Recombinant growth hormone treatment could also increase LM and decrease FM, as shown in 9 patients. DEXA appears therefore to be a reliable method for evaluating therapeutic interventions affecting nutritional status in children with CRF.

What about the renal function during childhood of children born from dialysed mothers?

INTRODUCTION

Pregnancy during dialysis is a high-risk condition which is becoming more and more common. The renal outcome of children born from such pregnancies needs to be investigated since renal development may be affected (i.e. exposure to uraemic toxins, therapies, intermittent haemodynamic changes during sessions, prematurity, growth retardation).

METHODS

We performed a single-centre prospective global and renal evaluation (inulin clearance or 2009 Schwartz formula in children <4 years) in 10 children from 7 mothers who underwent haemodialysis during pregnancy.

RESULTS

The median (range) age of mothers at the beginning of pregnancy was 30 (22-33) years, with maximal weekly haemodialysis duration of 18 (12-30) h. Systemic arterial hypertension was reported in 4 of 10 pregnancies, polyhydramnios in 3 and oligohydramnios in 1. The median (range) gestational age was 32 (29-39) weeks of gestation (WG). Seven children were born before 36 WG. The median (range) birth weight (BW) was 1735 (930-3430)g, and eight children had a BW <2500 g. One child had a PAX2 mutation requiring early renal transplantation and was thus excluded from further analysis. Even though glomerular filtration rate and blood pressure were normal in all other children, a significant urine albumin-to-creatinine ratio was found in three children and an increased urine beta-2-microglobulin concentration in an additional one, questioning the presence of an underlying silent reduction in nephron number.

CONCLUSIONS

Despite the small number of patients, this pilot study highlights the potential risk of renal impairment in children born from dialysed mothers. Further studies are required but until then, careful monitoring of these children is important.

Selection of transplantation procedures and perioperative management in primary hyperoxaluria type 1

This paper outlines the different options of transplant procedures in patients with primary hyperoxaluria type 1. Isolated kidney, isolated liver and combined liver-kidney grafting are discussed. Combined liver-kidney grafting appears to be the preferred treatment for patients already in end-stage renal failure. The potential value of the two other procedures is outlined. Guidelines for perioperative care are given. These involve fluid regime, pyridoxine supplementation, immunosuppression and administration of crystallization inhibitors such as phosphate and citrate. Special emphasis is put on selection of appropriate dialysis procedures and reasons why haemodialysis and continuous haemodiafiltration are the methods of choice.

Reduced elastogenesis: a clue to the arteriosclerosis and emphysematous changes in Schimke immuno-osseous dysplasia?

BACKGROUND

Arteriosclerosis and emphysema develop in individuals with Schimke immuno-osseous dysplasia (SIOD), a multisystem disorder caused by biallelic mutations in SMARCAL1 (SWI/SNF-related, matrix-associated, actin-dependent regulator of chromatin, subfamily a-like 1). However, the mechanism by which the vascular and pulmonary disease arises in SIOD remains unknown.

METHODS

We reviewed the records of 65 patients with SMARCAL1 mutations. Molecular and immunohistochemical analyses were conducted on autopsy tissue from 4 SIOD patients.

RESULTS

Thirty-two of 63 patients had signs of arteriosclerosis and 3 of 51 had signs of emphysema. The arteriosclerosis was characterized by intimal and medial hyperplasia, smooth muscle cell hyperplasia and fragmented and disorganized elastin fibers, and the pulmonary disease was characterized by panlobular enlargement of air spaces. Consistent with a cell autonomous disorder, SMARCAL1 was expressed in arterial and lung tissue, and both the aorta and lung of SIOD patients had reduced expression of elastin and alterations in the expression of regulators of elastin gene expression.

CONCLUSIONS

This first comprehensive study of the vascular and pulmonary complications of SIOD shows that these commonly cause morbidity and mortality and might arise from impaired elastogenesis. Additionally, the effect of SMARCAL1 deficiency on elastin expression provides a model for understanding other features of SIOD.

Identification of 5 novel mutations in the AGXT gene

In order to identify additional genotypes in primary hyperoxaluria type 1, we sequenced the AGXT genes of 9 patients. We report 5 new mutations. Three are splice-site mutations situated at the end of intron 4 and 8 (647-1G>A, 969-1G>C, 969-3C>G), one is a missense mutation in exon 5 (D183N), and one is a short duplication in exon 2 (349ins7). Their consequence is always a lack of enzymatic activity of the Alanine-Glyoxylate Aminotransferase (AGT); for 4 of them, we were able to deduce that they were associated to the absence of AGT protein. These mutations are rare, as they have been found on one allele in our study (except 969-3C>G present in 2 unrelated families), and have not been previously reported.

Familial infantile nephrotic syndrome with ocular abnormalities

Two siblings born from consanguineous parents experienced infantile nephrotic syndrome with ocular and neurological abnormalities; the boy also had a micropenis; both patients died before age 1 year. An initial renal biopsy followed by a two-step binephrectomy allowed good histological assessment of disease progression in one patient. The progression of the lesions was characterized by mesangial involvement, then an extensive extracapillary proliferation and tubular dilatations with a high mitotic activity of the epithelium and nuclei of unequal size. The main features involved major ultrastructural changes of the glomerular basement membrane. These two patients may represent a new disease entity or a severe form of diffuse mesangial sclerosis, with autosomal recessive inheritance.

Dental abnormalities in Schimke immuno-osseous dysplasia

Described for the first time in 1971, Schimke immuno-osseous dysplasia (SIOD) is an autosomal-recessive multisystem disorder that is caused by bi-allelic mutations of SMARCAL1, which encodes a DNA annealing helicase. To define better the dental anomalies of SIOD, we reviewed the records from SIOD patients with identified bi-allelic SMARCAL1 mutations, and we found that 66.0% had microdontia, hypodontia, or malformed deciduous and permanent molars. Immunohistochemical analyses showed expression of SMARCAL1 in all developing teeth, raising the possibility that the malformations are cell-autonomous consequences of SMARCAL1 deficiency. We also found that stimulation of cultured skin fibroblasts from SIOD patients with the tooth morphogens WNT3A, BMP4, and TGFβ1 identified altered transcriptional responses, raising the hypothesis that the dental malformations arise in part from altered responses to developmental morphogens. To the best of our knowledge, this is the first systematic study of the dental anomalies associated with SIOD.

Renal function can be impaired in children with primary hyperoxaluria type 3

BACKGROUND

Primary hyperoxaluria type 3 (PH3) is characterized by mutations in the 4-hydroxy-2-oxoglutarate aldolase (HOGA1) gene. PH3 patients are believed to present with a less severe phenotype than those with PH1 and PH2, but the clinical characteristics of PH3 patients have yet to be defined in sufficient detail. The aim of this study was to report our experience with PH3.

METHODS

Genetic analysis of HOGA1 was performed in patients with a high clinical suspicion of PH after the presence of mutations in the alanine-glyoxylate aminotransferase gene had been ruled out. Clinical, biochemical and genetic data of the seven patients identified with HOGA1 mutations were subsequently retrospectively reviewed.

RESULTS

Among the seven patients identified with HOGA1 mutations the median onset of clinical symptoms was 1.8 (range 0.4-9.8) years. Five patients initially presented with urolithiasis, and two other patients presented with urinary tract infection. All patients experienced persistent hyperoxaluria. Seven mutations were found in HOGA1, including two previously unreported ones, c.834 + 1G > T and c.3G > A. At last follow-up, two patients had impaired renal function based on estimated glomerular filtration rates (GFRs) of 77 and 83 mL/min per 1.73 m(2), respectively.

CONCLUSIONS

We found that the GFR was significantly impaired in two of our seven patients with PH3 diagnosed during childhood. This finding is in contrast to the early-impaired renal function in PH1 and PH2 and appears to refute to preliminary reassuring data on renal function in PH3.

Longitudinal growth in children following kidney transplantation: from conservative to pharmacological strategies

Impairment of longitudinal growth in children with chronic renal failure (CRF) is multifactorial. It is mainly due to disturbances in the growth hormone (GH)/insulin-like growth factor (IGF)/IGF-binding protein axis. Growth failure can be managed by optimizing nutrition and fluid/electrolyte homeostasis, and overcoming the growth-inhibiting effects of uremia by high-dose recombinant human (rh) GH treatment. A sufficient catch-up growth is one of the determining issues for the overall success of pediatric kidney transplantation (Tx). However, despite satisfactory renal function, spontaneous catch-up growth is often insufficient as glucocorticoid treatment is the main inhibiting factor for longitudinal growth after Tx. In addition, longitudinal growth may be jeopardized by low glomerular filtration rate (GFR) and African American or Hispanic background. Supraphysiological doses of GH and/or IGF-I in vitro and in vivo can partially overcome the growth-inhibiting effects of glucocorticoid treatment. GH-associated increase of leukocyte proliferation and cytotoxicity with stimulated interferon synthesis have been demonstrated. However, it is not clear whether such stimulatory effects on leukocyte function are a transitory or a constant risk factor after organ Tx. Clinical trials of GH in children after renal Tx have suggested a rather moderate or transient effect of rhGH on the immune system, and corticosteroids induce a hyporesponsiveness to the action of GH. As long as corticosteroids are believed to be essential after renal Tx, rhGH should be considered to optimize longitudinal growth in children.

Towards adulthood with a solitary kidney

Around 1/1000 people have a solitary kidney. Congenital conditions mainly include multicystic dysplastic kidney and unilateral renal aplasia/agenesis; acquired conditions are secondary to nephrectomy performed because of urologic structural abnormalities, severe parenchymal infection, renal trauma, and renal or pararenal tumors. Children born with congenital solitary kidney have a better long-term glomerular filtration rate than those with solitary kidney secondary to nephrectomy later in life. Acute and chronic adaptation processes lead to hyperfiltration followed by fibrosis in the remnant kidney, with further risk of albuminuria, arterial hypertension, and impaired renal function. Protective measures rely on non-pharmacological renoprotection (controlled protein and sodium intake, avoidance/limitation of nephrotoxic agents, keeping normal body mass index, and limitation of tobacco exposure). Lifelong monitoring should include blood pressure and albuminuria assessment, completed by glomerular filtration rate (GFR) estimation in case of abnormal values. In the absence of additional risk factors to solitary kidney, such assessment can be proposed every 5 years. There is no current consensus for indication and timing of pharmacological intervention.

[Childhood-onset systemic lupus erythematosus]

Systemic Lupus Erythematosus (SLE) remains a challenging autoimmune disease in term of etiology, pathogenesis and treatment. It is estimated that 10-17% of lupus patients present before the age of 16. SLE in children appears to have more severe organ involvement than in adults. The outcome of childhood SLE has improved during the last decade, but the morbidity remains high.

Overexpression of the antiapoptotic gene Bfl-1 in B cells from patients with familial systemic lupus erythematosus

Genetic determinants taking part in the development of systemic lupus erythematosus (SLE) are complex and not fully characterized. Dysregulated expression of genes involved in the control of apoptosis has been previously suggested. We report here a consanguineous family with SLE manifestations in three siblings associated in one of them with severe lymphoproliferative features. Laboratory studies showed no defect in CD95-mediated cell death. Screening expression of Bcl-2 family genes that regulate mitochondrial apoptosis pathway showed an overexpression of the antiapoptotic Bfl-1 gene. Real time RT-PCR analysis indicated that overexpression of Bfl-1 was restricted to B-cells, with normal expression in T-cells. Those results suggest that overexpression of Bfl-1 could result in impaired B-lymphocyte homeostasis and inappropriate immune response leading to autoimmune manifestations.

Neonatal hemolytic uremic syndrome after mother-to-child transmission of Escherichia coli O157

About 90% of cases of hemorrhagic uremic syndrome (HUS) occur in early childhood and most frequently are preceded by bloody diarrhea due to shiga-like toxin (SLT) producing Escherichia coli. We report a case of a newborn girl presenting with bloody diarrhea on her 7th day of life. Acute renal failure, severe arterial hypertension and hemolytic anemia were detected and prompt peritoneal dialysis and antihypertensive therapy were required. The girl had several episodes of seizures, necessitating intravenous phenobarbital. Transfontanel ultrasonography 48 h after disease onset was normal, whereas, MRI investigation 10 days later revealed severe ischemic lesions with beginning cystic encephalopathy. Renal function recovered and only very moderate tubular dysfunction remained. Serum analysis of factor H, von Willebrand factor protease, homocystinemia, proteins C and S, and antithrombin III were all normal. Mutation analysis of factor V Leiden, factor II, and methyltetrahydrofolate-reductase were normal. E. coli 0157:H7 and SLT 2 were detected in the stool. SLT 2 was also found in the mother's stool. This is the first report of mother-to-child transmission of SLT-producing E. coli.

Survey of the attitudes to management of acute pyelonephritis in children. GEP

Although urinary tract infections are of particular concern in young children, as they may lead to permanent health problems, there is no consensus for their acute management. We carried out a mailed survey of 455 general practitioners, 143 paediatricians (randomly selected from a list of physicians in the Rhône-Alpes region of France) and 45 paediatric nephrologists (all the members of the "Société de Néphrologie Pédiatrique") to examine their attitudes to the management of a fictitious case of a young girl with symptoms indicative of acute pyelonephritis. The responses given by the general practitioners and paediatricians were similar, whereas those given by the paediatric were similar, whereas those given by the paediatric nephrologists were often different, for example 20% of the general practitioners and 17% of the paediatricians said they would hospitalize the child, compared with 69% of the paediatric nephrologists. The majority of the general practitioners and paediatricians favoured single oral antibiotic therapy, whereas the paediatric nephrologists were split between single and combined antibiotic therapy, but preferred intravenous administration. The most frequently prescribed drug was a penicillin. The heterogeneity of the results from this survey stresses the need for the assessment of various strategies in terms of their efficacy for preventing kidney scarring and their risk-to-benefit ratios in well-designed randomised controlled trials.

Maternal isodisomy of the telomeric end of chromosome 2 is responsible for a case of primary hyperoxaluria type 1

Primary hyperoxaluria type 1 (PH1) is an autosomal recessive disorder of glyoxylate metabolism, in which excessive oxalates are formed by the liver and excreted by the kidneys, causing a wide spectrum of disease, ranging from renal failure in infancy to mere renal stones in late adulthood. This disease is caused by a deficiency of alanine:glyoxylate aminotransferase (AGT), which is encoded by a single copy gene, AGXT, located in 2q37.3. We identified an apparently homozygous, loss-of-function, mutation in a patient; the gene defect was present in the heterozygous mother but not in the patient's father. We performed a microsatellite repeat analysis using 13 specific chromosome 2 markers and non-chromosome 2 minisatellites. Six specific chromosome 2 markers showed an apparently homozygous maternal inheritance while four showed a biparental transmission consistent with paternity (confirmed by minisatellite analysis). Quantitative PCR of AGXT exons 1 and 3 on the patient's and parents genomic DNA revealed the presence of two copies of the gene. This is the first case of PH1 caused by segmental maternal isodisomy of 2q37.3.

Munchausen syndrome by proxy with massive proteinuria and gastrointestinal hemorrhage

A 5-year-old boy presented with acute abdominal pain. Massive proteinuria of 10 g/1.73 m(2) per day was detected on standard urinalysis. There was no peripheral edema. Serum concentrations of total proteins, lipids, and creatinine and immunological investigations were normal. Two kidney biopsies revealed no abnormalities. Several weeks later he was admitted for intestinal hemorrhage with significant anemia. Endoscopy of the esophagus, stomach, colon, and small bowel (via laparotomy) were normal. Electrophoresis of urine proteins revealed the unusual finding of an albumin fraction of 99.4%. During a routine check-up in the outpatient clinic fresh urine samples were obtained while the boy's mother was absent. These were all negative for protein. The mother, who was a nurse, finally confessed to adding human albumin to the urine samples.

Acute renal failure in a child after chewing of match heads

A few days after ingestion of 40 match heads, a 3-year-old boy was admitted to hospital with oliguric acute renal failure (ARF) requiring peritoneal dialysis during 9 days. A renal biopsy showed acute tubulointerstitial nephritis; the outcome was rapidly favorable and the child recovered normal GFR. It seems to be the first published case of ARF after match poisoning, probably because of the presence of potassium bichromate.

Body composition in children after renal transplantation

This study examines changes in body composition after renal transplantation (Tx) in 16 children who underwent dual-energy X-ray absorptiometry examination within 6 months preceding Tx; the examination was then repeated every 6 to 12 months after Tx. Body composition was analyzed with regard to whole-body bone mineral content (BMC), lean body mass (LBM), and fat body mass (FBM). Median BMC decreased from the initial value of +0.98 standard deviation scores (SDS) to -0.55 SDS during the first 3 months after Tx, and a further decrease was noted at the end of month 6 (M6; -1.34 SDS) and M12 after Tx (-1.32 SDS). Improvement was observed during the second year after Tx (P for global changes < 0.0001). LBM and FBM also changed significantly during the 2 years after Tx (P = 0.006 and P = 0.0001, respectively). LBM decreased during the first 3 months after Tx (median change, 0.71 SDS) and remained less than 0 SDS in all but 4 patients. Median LBM did not decrease to less than -1 SDS during the entire study period. Conversely, median FBM increased by a median of 3.73 SDS during the first 3 months and remained elevated during the first 12 months after Tx, with a subsequent decrease at 2 years after Tx. No significant correlation was found between cumulative doses of prednisone and BMC, FBM, or LBM at any interval if absolute values were considered. However, relative changes in FBM correlated significantly with relative changes in prednisone cumulative doses.