Mutant chromatin remodeling protein SMARCAL1 causes Schimke immuno-osseous dysplasia.

Schimke immuno-osseous dysplasia (SIOD, MIM 242900) is an autosomal-recessive pleiotropic disorder with the diagnostic features of spondyloepiphyseal dysplasia, renal dysfunction and T-cell immunodeficiency. Using genome-wide linkage mapping and a positional candidate approach, we determined that mutations in SMARCAL1 (SWI/SNF2-related, matrix-associated, actin-dependent regulator of chromatin, subfamily a-like 1), are responsible for SIOD. Through analysis of data from persons with SIOD in 26 unrelated families, we observed that affected individuals from 13 of 23 families with severe disease had two alleles with nonsense, frameshift or splicing mutations, whereas affected individuals from 3 of 3 families with milder disease had a missense mutation on each allele. These observations indicate that some missense mutations allow retention of partial SMARCAL1 function and thus cause milder disease.

Idiopathic midaortic syndrome: normalization of blood pressure on medication.

Midaortic syndrome (MAS) is a rare, idiopathic condition in children usually presenting with severe hypertension. We report a case of a 13-year-old girl who presented with severe hypertension (200/110 mmHg) associated with renal artery stenosis and normal renal function (creatinine clearance 110 ml/min/1.73m(2)). Percutaneous angioplasty (PTA) was first performed, but early recurrence of hypertension occurred. Subsequent imaging evaluation demonstrated association of aortic narrowing, proximal stenosis of the left renal artery, and wall thickening of superior mesenteric artery and right common carotid artery. Although previous large-vessel arteritis cannot be absolutely excluded, a diagnosis of idiopathic MAS was made, given the absence of any other clinical signs of inflammation (C-reactive protein <0.5 mg/dl; erythrocyte sedimentation rate 5 mm/h). Medical treatment was undertaken without repeat PTA or surgery. Blood pressure control was good, and antihypertensive therapy was stopped 4 years later. At age 22, the patient was still normotensive and receiving no antihypertensive therapy; normalization of Doppler velocities in the proximal left renal artery was confirmed. In the absence of renal dysfunction or target-organ damage, medical management of hypertension in MAS is feasible without intervention if blood pressure is well controlled on two antihypertensive agents.

Mycophenolate mofetil for steroid-dependent nephrotic syndrome: a phase II Bayesian trial.

Mycophenolate mofetil (MMF) has emerged as a new therapeutic option in steroid-dependent nephrotic syndrome (SDNS). We conducted a phase II Bayesian trial of MMF in children with SDNS. Phase II trials, usually single-arm studies, investigate the effect of new treatments. Standard Fleming's procedure relies on observed results (relapse rate during the trial), whereas Bayesian approach combines observed results with prior information (expected relapse rate according to prior studies and clinical experience). All patients were required to have received prior alkylating-agent treatment. Sixty-seven percent of them had also received levamisole. Patients received MMF (1,200 mg/m(2)/day) and prednisone according to a defined schedule [reduction of alternate-day (e.o.d) dose to 50% of pre-MMF dose at 3 months, 25% at 6 months]. Twenty-four children (median age 6.0 years, 2.8-14.4) entered the study and 23 completed it. Bayesian analysis showed that adding four patients would not change significance of results, allowing stopping inclusions. Four patients relapsed during the first 6 months (estimated probability 17.6%, 95% credibility interval: 5.4-35.0%) and two at months 8 and 11.5. In the 19 patients free of relapse during the first 6 months, median (Q1-Q3) prednisone maintenance dose decreased from 25 (10-44) to 9 (7.5-11.2) mg/m(2) e.o.d (p < 0.001) and cumulative dose from 459 (382-689) to 264 (196-306) mg/m(2)/month (p < 0.001) before and on MMF respectively. Pre-MMF patient characteristics and MMF pharmacokinetics did not differ between patients with or without relapse. MMF reduces relapse rate and steroid dose in children with SDNS and should be proposed before cyclosporine and cyclophosphamide.

Clinical features of anti-factor H autoantibody-associated hemolytic uremic syndrome.

Atypical hemolytic uremic syndrome (aHUS) is a rare form of thrombotic microangiopathy that associates, in 70% of cases, with genetic or acquired disorders leading to dysregulation of the alternative pathway of complement. Autoantibody directed against Factor H causes at least 6% to 10% of aHUS cases, but only a few clinical reports are available. Here, we describe the clinical, biologic, genetic features, treatment, and outcome of 45 patients who presented with aHUS associated with anti-FH autoantibody. We found that this form of aHUS primarily affects children between 9 and 13 years old but it also affects adults. It presents with a high frequency of gastrointestinal symptoms and with extrarenal complications and has a relapsing course. Activation of the alternative pathway of complement at the onset of disease portends a poor prognosis. Early specific treatment may lead to favorable outcomes. These data should improve the recognition and diagnosis of this form of aHUS and help identify patients at high risk of a poor outcome.

Population pharmacokinetics and Bayesian estimator of mycophenolic acid in children with idiopathic nephrotic syndrome.

AIMS: To develop a population pharmacokinetic model for mycophenolic acid (MPA) in children with idiopathic nephrotic syndrome (INS) treated with mycophenolate mofetil (MMF), identify covariates that explain variability and determine the Bayesian estimator of the area under the concentration-time curve over 12 h (AUC(0-12)). METHODS: The pharmacokinetic model of MMF was described from 23 patients aged 7.4 +/- 3.9 years (range 2.9-14.9) using nonlinear mixed-effects modelling (NONMEM) software. A two-compartment model with lag-time and first-order absorption and elimination was developed. The final model was validated using visual predictive check. Bayesian estimator was validated using circular permutation method. RESULTS: The population pharmacokinetic parameters were apparent oral clearance 9.7 l h(-1), apparent central volume of distribution 22.3 l, apparent peripheral volume of distribution 250 l, inter-compartment clearance 18.8 l h(-1), absorption rate constant 5.16 h(-1), lag time 0.215 h. The covariate analysis identified body weight and serum albumin as individual factors influencing the apparent oral clearance. Accurate Bayesian estimation of AUC(0-12) was obtained using the combination of three MPA concentrations measured just before (T(0)), 1 and 4 h (T(1) and T(4)) after drug intake with a small error of 0.298 microg h(-1) ml(-1) between estimated and reference AUC(0-12). CONCLUSIONS: The population pharmacokinetic model of MPA was developed in children with INS. A three-point (T(0), T(1) and T(4)h) Bayesian estimator of AUC(0-12) was developed and might be used to investigate the relation between MPA pharmacokinetic and pharmacodynamics in children with INS and determine if there is any indication to monitor MPA exposure in order to improve patient outcome based on individual AUC-controlled MMF dosing.

Schimke immunoosseous dysplasia: defining skeletal features.

Schimke immunoosseous dysplasia (SIOD) is an autosomal recessive multisystem disorder characterized by prominent spondyloepiphyseal dysplasia, T cell deficiency, and focal segmental glomerulosclerosis. Biallelic mutations in swi/snf-related, matrix-associated, actin-dependent regulator of chromatin, subfamily a-like 1 (SMARCAL1) are the only identified cause of SIOD, but approximately half of patients referred for molecular studies do not have detectable mutations in SMARCAL1. We hypothesized that skeletal features distinguish between those with or without SMARCAL1 mutations. Therefore, we analyzed the skeletal radiographs of 22 patients with and 11 without detectable SMARCAL1 mutations. We found that patients with SMARCAL1 mutations have a spondyloepiphyseal dysplasia (SED) essentially limited to the spine, pelvis, capital femoral epiphyses, and possibly the sella turcica, whereas the hands and other long bones are basically normal. Additionally, we found that several of the adolescent and young adult patients developed osteoporosis and coxarthrosis. Of the 11 patients without detectable SMARCAL1 mutations, seven had a SED indistinguishable from patients with SMARCAL1 mutations. We conclude therefore that SED is a feature of patients with SMARCAL1 mutations and that skeletal features do not distinguish who of those with SED have SMARCAL1 mutations.

Schimke immunoosseous dysplasia: suggestions of genetic diversity.

Schimke immunoosseous dysplasia (SIOD), which is characterized by prominent spondyloepiphyseal dysplasia, T-cell deficiency, and focal segmental glomerulosclerosis, is a panethnic autosomal recessive multisystem disorder with variable expressivity. Biallelic mutations in switch/sucrose nonfermenting (swi/snf) related, matrix-associated, actin-dependent regulator of chromatin, subfamily a-like 1 (SMARCAL1) are the only identified cause of SIOD. However, among 72 patients from different families, we identified only 38 patients with biallelic mutations in the coding exons and splice junctions of the SMARCAL1 gene. This observation, the variable expressivity, and poor genotype-phenotype correlation led us to test several hypotheses including modifying haplotypes, oligogenic inheritance, or locus heterogeneity in SIOD. Haplotypes associated with the two more common mutations, R820H and E848X, did not correlate with phenotype. Also, contrary to monoallelic SMARCAL1 coding mutations indicating oligogenic inheritance, we found that all these patients did not express RNA and/or protein from the other allele and thus have biallelic SMARCAL1 mutations. We hypothesize therefore that the variable expressivity among patients with biallelic SMARCAL1 mutations arises from environmental, genetic, or epigenetic modifiers. Among patients without detectable SMARCAL1 coding mutations, our analyses of cell lines from four of these patients showed that they expressed normal levels of SMARCAL1 mRNA and protein. This is the first evidence for nonallelic heterogeneity in SIOD. From analysis of the postmortem histopathology from two patients and the clinical data from most patients, we propose the existence of endophenotypes of SIOD.

Sudden blindness caused by anterior ischemic optic neuropathy in 5 children on continuous peritoneal dialysis.

The authors report the occurrence of sudden blindness in 5 children (mean age, 32 months; range, 11 to 60) during continuous peritoneal dialysis regimen. All children presented with loss of light perception, visual fixation and ocular pursuit, and bilateral mydriasis unreactive to bright light. Fundoscopic examination found signs of anterior ischemic optic neuropathy with disc swelling, edema, and hemorrhages. Whereas 1 patient was dehydrated, the 4 other patients appeared well and not dehydrated. Nevertheless, blood pressure was below the normal range in all of them. Therefore, hypovolemia is highly suspected to have been the cause of ischemic optic neuropathy in all cases. Treatment consisted of steroids (4 patients), anticoagulation or antiagregation drugs (3 patients), plasma or macromolecules infusions (2 patients), vasodilatators (2 patients), and transient dialysis interruption (1 patient). One child with hepatic cirrhosis died 4 days later of acute liver insufficiency owing to ischemic hepatic necrosis. The other children had only partial improvement of vision during the following months. Because the prognosis of ischemic optic neuropathy is very poor, diagnosis and treatment of chronic hypovolemia in children on continuous peritoneal dialysis is essential to prevent such a devastating complication.

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.

Population pharmacokinetics and pharmacogenetics of mycophenolic acid following administration of mycophenolate mofetil in de novo pediatric renal-transplant patients.

The objective was to develop a population pharmacokinetic-pharmacogenetic model of mycophenolic acid following administration of mycophenolate mofetil (MMF) in de novo pediatric renal-transplant patients and identify factors that explain variability. The pharmacokinetic samples were collected from 89 de novo pediatric renal-transplant patients treated with MMF and studied during the first 60 postoperative days. All patients were genotyped for UGT1A8-A9, UGT2B7, and ABCC2. Population pharmacokinetic analysis was performed with the NONMEM and was validated using bootstrap visual predictive check. The pharmacokinetic data were best described by a 2-compartment model with Erlang distribution to describe the absorption phase. The covariate analysis identified body weight as an individual factor influencing central volume of distribution and concomitant immunosuppressive medication and identified body weight and UGT2B7 802C>T genotype as individual factors influencing apparent oral clearance (CL/F) of MMF. CL/F in cyclosporine-MMF-treated patients was 33% higher than in tacrolimus-MMF-treated patients. The CL/F was significantly lower in patients with UGT2B7 802 C/C genotype compared with patients with UGT2B7 802 C/T and 802T/T genotypes, and this effect was independent of concomitant immunosuppressive medication or body weight. The population pharmacokinetic-pharmacogenetic model of mycophenolic acid was validated. Body weight, concomitant medication, and UGT2B7 genotype contribute significantly to the interindividual variability of MMF disposition in pediatric renal-transplant patients.

Long-term results of rhGH treatment in children with renal failure: experience of the French Society of Pediatric Nephrology.

Few publications have described the long-term effects of recombinant human growth hormone (rhGH) in uremic patients. This study reports the results of rhGH therapy at the end of treatment and at adult age in 178 French patients. At enrollment, 63 patients were under conservative treatment (CT), 40 under hemodialysis (HD), and 75 had a functioning renal transplant (RT). Under rhGH treatment, height velocities (HV) significantly increased in all patients, but the effect was significantly better in the CT group. The HV gain (HV under rhGH-HV before treatment) was similar in all three groups. Increases in HV allowed height standard deviation scores (SDS) catch up, and this effect persisted over a 5-year period. SDS height at the completion of treatment was significantly related to group (best in CT) and response to treatment during the first year. Data on adult height was available for 102 patients. Mean adult height was 162.2 cm in men and 152.9 cm in women, and 46% were > -2 SDS for height. Adult height SDS was correlated with height SDS and spontaneous HV before treatment and effect of treatment. Analysis of adult height in the 49 patients who entered the protocol with a height SDS between -2 and -3 (the current recommendation for rhGH use) revealed that 65% had an adult-height SDS >-2. These adult heights were significantly better if compared with historical cohorts of patients not treated by rhGH; rhGH significantly improves the adult-height prognosis of uremic patients suffering from growth retardation. Early rhGH administration during CT gives better height SDS at both the end of rhGH therapy and in adulthood.

Darbepoetin, effective treatment of anaemia in paediatric patients with chronic renal failure.

Darbepoetin alpha (DA) is a unique long-acting treatment for anaemia in patients with chronic renal failure (CRF). This study assessed the mean dose of DA to achieve and maintain haemoglobin (Hb) levels between 11 g/dl and 13 g/dl in CRF children aged 11 years to 18 years. This observational, prospective study was conducted in 39 patients treated with DA. Twenty-nine patients were switched from recombinant human erythropoietin (r-HuEPO), and ten patients were naive to r-HuEPO. Naive patients received initial doses of 0.45 microg/kg of DA. Switched patients received a dose adjusted to the prior dose of r-HuEPO (200 IU r-HuEPO:1 microg DA). Among the switched patients, 79.3% received dialysis. No naive patients underwent dialysis. Overall, 74% of patients showed increased Hb level, with a mean value of 11.6 +/- 1.6 g/dl, using a mean DA dose of 0.63 +/- 0.48 microg/kg per week, and 66.7% patients reached the target Hb level. Hb increased in naive patients from 9.5 (95% CI: 7.7, 11.4) to 11.7 (95% CI: 10.9, 12.6) g/dl and in switched patients from 11.1 (95% CI: 10.6, 11.5) to 11.5 (95% CI: 10.8, 12.2) g/dl). Higher doses of DA were needed in the "switched" than in the "naive" patients to maintain Hb levels over 11 g/dl, respectively 0.73 (95% CI: 0.54, 0.92) and 0.34 (95% CI: 0.16, 0.52) microg/kg per week. Our results indicate the doses of DA necessary to treat CRF patients aged 11 years to 18 years. DA was an effective treatment to stabilise CRF patients at extended dosing intervals.

Recurrence of nephrotic syndrome after renal transplantation: influence of increased immunosuppression.

Recurrence of nephrotic syndrome after renal transplantation leads to graft loss within 1 year in 50-80% of patients who do not receive any specific treatment. Several treatment protocols have been proposed leading to long-term remission in 50-80% of patients. The aim of our study was to evaluate the efficiency of intensified immunosuppression, simultaneously including methylprednisolone pulses, cyclophosphamide, high-dose cyclosporine and plasma exchanges. Fourteen patients with early recurrence were treated with a protracted high-dose prednisone or IV methylprednisolone, oral cyclophosphamide, high-dose oral or IV cyclosporine, and plasma exchanges. By the end of cyclophosphamide therapy and plasma-exchange program, six out of 14 patients had no proteinuria; five had residual proteinuria without nephrotic syndrome and three experienced ongoing gross proteinuria with nephrotic syndrome. By the end of follow-up, four out of the 14 patients had lost their graft: one out of six with complete remission, one out of five with residual proteinuria and two out of three with persistent nephrotic syndrome. We conclude that multiple reinforcement of immunosuppression in patients with recurrent nephrotic syndrome following renal transplantation as performed in our patients is not more efficient than the single use of cyclophosphamide or plasma exchange or high-dose cyclosporine as reported in the literature.

Long-term follow-up of Epstein-Barr virus viremia in pediatric recipients of renal transplants.

The common observation of Epstein-Barr virus (EBV) viremia in pediatric recipients of renal transplants and the occurrence of an EBV-related pulmonary leiomyoma prompted us to intensify the follow-up of EBV infections from 1995 to October 2000. Follow-up included serology and detection of viral DNA in blood using a semi-quantitative nested polymerase chain reaction (PCR) and later a real-time PCR with higher sensitivity. The aim of this study was the early detection of primary infections or reactivations. We obtained 250 samples from 32 patients. EBV DNA detection was consistently negative in 14 patients. There were 5 patients that were considered at risk for post-transplant lymphoproliferative disease, as they were EBV seronegative and were given a kidney from a positive donor. Of these, 4 had at least one episode of high-level EBV viremia. During these episodes, an absence of noticeable symptoms that could be related to EBV was noted for all but 1 patient. This child presented with severe neutropenia 1 month after grafting and, 28 months later, several nodules of pulmonary leiomyoma, which were found to be EBV related. Four episodes of high-level viremia were observed before the discovery of the leiomyoma. Viral DNA detection is important for the follow-up of such patients that are especially at risk of serious complications of EBV infections.

Association of migraine-like headaches with Schimke immuno-osseous dysplasia.

Schimke immuno-osseous dysplasia (SIOD) is characterized by spondyloepiphyseal dysplasia, nephropathy, and T-cell deficiency. SIOD is caused by mutations in the putative chromatin remodeling protein SMARCAL1. We report an 8-year-old boy with SIOD and recurrent, severe, refractory migraine-like headaches. Through a retrospective questionnaire-based study, we found that refractory and severely disabling migraine-like headaches occur in nearly half of SIOD patients. We have also found that the vasodilator minoxidil provided symptomatic relief for one patient. We hypothesize that these headaches may arise from an intrinsic vascular, neuroimmune, or neurovascular defect resulting from loss of SMARCAL1 function.

Final height in children with chronic renal failure who have not received growth hormone.

Final height (FH), growth velocity after 16 and 18 years of age, and factors predictive for FH were assessed in 60 patients (21-36 years old), whose chronic renal failure (CRF) started before the age of 16 years (28 girls and 32 boys). At 16 years of age, 22 had conservative treatment (CT, group A) and 38 end-stage renal failure [ESRF, group B, which includes 19 receiving hemodialysis (HD) and 19 with a functional renal transplant (RTx)]. None received recombinant human growth hormone (rhGH) treatment. FH was lower than in a normal population: 161.6+/-8 cm for males [-2.06+/-1.3 standard deviation score (SDS)] and 154.3+/-8.1 cm for females (-1.4+/-1.4 SDS). FH in group A (-1.15+/-1.4 SDS) was significantly higher than in group B (-2.1+/-1.3 SDS); 45% of all patients (56% of males and 23% of females) had a final height below -2 SDS (41% in group A and 47% in group B). FH was reached at 20.2+/-1.8 years in males and 18.8+/-2 years in females. A continuation of growth after 18 years of age was observed in 23 males (71.8%): +5.2 cm (+0.87 SDS) and in 14 females (50%): +1.75 cm (+0.3 SDS). However, this partial recovery concerned mainly patients with an important growth deficiency. A higher height at enrolment or at ESRF was significantly associated with a higher FH, whereas a longer period of ESRF had a significantly negative effect. In conclusion, all efforts should be made to diagnose CRF as early as possible and to try to improve growth before ESRF and RTx. Early institution of rhGH therapy should improve FH and improve the chance of achieving near-normal adult height in most patients.

Transient hyperphosphatasemia after organ transplantation in children.

Transient, isolated hyperphosphatasemia is a rare, benign condition of childhood. Few cases have been described in transplant patients. We report six cases: three after liver transplantation and three after kidney transplantation. Such a phenomenon was found to be as benign after organ transplantation as it is in healthy children. Hence, an isolated increase in the serum alkaline phosphatase level following transplantation should not be of concern in this population of patients.