Long-term renal outcome in children with OCRL mutations: retrospective analysis of a large international cohort.

Background: Lowe syndrome (LS) and Dent-2 disease (DD2) are disorders associated with mutations in the OCRL gene and characterized by progressive chronic kidney disease (CKD). Here, we aimed to investigate the long-term renal outcome and identify potential determinants of CKD and its progression in children with these tubulopathies. Methods: Retrospective analyses were conducted of clinical and genetic data in a cohort of 106 boys (LS: 88 and DD2: 18). For genotype-phenotype analysis, we grouped mutations according to their type and localization. To investigate progression of CKD we used survival analysis by Kaplan-Meier method using stage 3 CKD as the end-point. Results: Median estimated glomerular filtration rate (eGFR) was lower in the LS group compared with DD2 (58.8 versus 87.4 mL/min/1.73 m2, P < 0.01). CKD stage II-V was found in 82% of patients, of these 58% and 28% had moderate-to-severe CKD in LS and DD2, respectively. Three patients (3%), all with LS, developed stage 5 of CKD. Survival analysis showed that LS was also associated with a faster CKD progression than DD2 (P < 0.01). On multivariate analysis, eGFR was dependent only on age (b = -0.46, P < 0.001). Localization, but not type of mutations, tended to correlate with eGFR. There was also no significant association between presence of nephrocalcinosis, hypercalciuria, proteinuria and number of adverse clinical events and CKD. Conclusions: CKD is commonly found in children with OCRL mutations. CKD progression was strongly related to the underlying diagnosis but did not associate with clinical parameters, such as nephrocalcinosis or proteinuria.

Characterization of 28 novel patients expands the mutational and phenotypic spectrum of Lowe syndrome.

BACKGROUND: The oculocerebrorenal syndrome of Lowe (OCRL) is a rare X-linked multi-systemic disorder, almost always characterized by the triad of congenital cataract, cognitive and behavioral impairment and a proximal tubulopathy. METHODS: Twenty-eight novel patients with suspected Lowe syndrome were studied. RESULTS: All patients carried OCRL gene defects with mutational hot spots at CpG dinucleotides. Mutations previously unknown in Lowe syndrome were observed in ten of the 28 patients, and carriership was identified in 30.4 % of the mothers investigated. Mapping the exact breakpoints of a complete OCRL gene deletion revealed involvement of several flanking repeat elements. We noted a similar pattern of documented clinically relevant symptoms, and even though the patient cohort comprised relatively young patients, 32 % of these patients already showed advanced chronic kidney disease. Thrombocytopenia was seen in several patients, and hyperosmia and/or hyperacusis were reported recurrently. A p.Asp523Asn mutation in a Polish patient, associated with the typical cerebrorenal spectrum but with late cataract (10 year), was also evident in two milder affected Italian brothers with ocular involvement of similar progression. CONCLUSIONS: We have identified clinical features in 28 patients with suspected Lowe syndrome that had not been recognized in Lowe syndrome prior to our study. We also provide further evidence that OCRL mutations cause a phenotypic continuum with selective and/or time-dependent organ involvement. At least some of these mutants might exhibit a genotype-phenotype correlation.

Do children with end-stage renal disease live shorter? Analysis of mortality on the basis of data from the Polish Registry of Renal Replacement Therapy in Children.

PURPOSE: The mortality of patients with end-stage renal disease (ESRD) is much higher than that of the general population. To date no data has been published on the mortality of children with ESRD in Poland. The aim of this study was to compare the risk of death for pediatric patients on renal replacement therapy (RRT) with that of the general pediatric population and to identify the risk factors of death. MATERIAL/METHODS: Data of 779 children with ESRD registered in the Polish Registry of Children on RRT was analyzed. The relative risk of death was calculated as the ratio of the mortality rate in ESRD patients to the mortality rate in age-adjusted general population. RESULTS: The mortality rate of children with ESRD was 74-fold higher than that of the age- and gender-adjusted general pediatric population (4.05 vs. 0.05/100 person-years). The highest mortality rate (4.53/100 patient-years) was found in the youngest age group. Younger age and duration of dialysis therapy were identified as mortality risk factors. The major causes of death in ESRD patients were infections and cardiovascular complications, whereas deaths in general child population were mainly due to accidents or congenital defects. CONCLUSIONS: The mortality in Polish children with ESRD is 74-fold higher than that of the general pediatric population. Infections, followed by cardiovascular complications, constitute the main causes of mortality in children subjected to RRT. The risk of death is the highest among children who started RRT at a younger age and in those subjected to long-term dialysis treatment.

[Congenital and genetic related causes of end-stage renal disease--data from Polish Registry of Renal Rreplacement Therapy in Children 2000-2004]. / Genetycznie uwarunkowane i wrodzone choroby nerek prowadzace do schylkowej niewydolnosci nerek--dane z polskiego rejestru dzieci leczonych nerkozastepczo (2000-2004).

UNLABELLED: One of the objectives of Polish Registry of Renal Replacement Therapy in Children established on 31st Dec. 2000 was to collect complete data on etiology of end stage renal disease (ESRD) in polish children. MATERIAL AND METHODS: Data on 469 patients (251 boys, 218 girls) aged 0-22 years treated with renal replacement therapy (RRT) at 13 pediatric dialysis units in Poland from 2000 to 2004 were analyzed. The mean age at start of dialysis was 10 years and 3 months. Renal diseases were defined according to EDTA coding system. Data is presented for the whole group, in 5-year age groups and separately for both sexes. RESULTS: Congenital and genetic renal diseases were the cause of ESRF in 56% of the polish population of children and adolescents on RRT. 39% of causes were acquired diseases, 5% remained unidentified. Congenital and genetic causes dominated in children < 5 years of age (71%). They accounted for 49%, 61% and 45% of causes in the consecutive 5-year age groups. The most numerous group of congenital diseases leading to ESRF were uropathies 37% and 25% of causes in the consecutive age groups. In boys the most frequent uropathy was obstructive uropathy (25%), the majority caused by posterior urethral valves. In girls the most frequent uropathies were reflux nephropathy (10%) and nephropathy secondary to neurogenic bladder (9%). Uropathies were followed by renal hypo-dysplasia without urinary tract anomalies (11%) and cystic diseases (10%). CONCLUSIONS: Congenital kidney anomalies and genetic diseases are the leading cause of end-stage renal disease in children up to 15 years of age.

Does a late referral to a nephrologist constitute a problem in children starting renal replacement therapy in Poland?--a nationwide study.

BACKGROUND: It is estimated that 20-50% of adult patients start chronic dialysis therapy without prior contact with a nephrologist. The aim of this nationwide study was to assess clinical and metabolic status of children at the start of chronic dialysis in Poland with regard to the timing of the referral to a nephrologist. METHODS: We studied data of 180 children (mean age 14+/-6 years) undergoing chronic dialysis in 13 (out of 14) dialysis pediatric centres in Poland. Patients were classified as early referrals (ERs) when they entered the dialysis programme at least 1 month after the first referral to a nephrologist or late referrals (LRs) when the dialysis was introduced within 1 month from the first visit. RESULTS: Seventy-nine percent of pediatric patients were referred early (ER) to the dialysis centre and 21% were referred late (LR) and had to start dialysis within a month. When starting dialysis, LR patients had significantly higher levels of urea and phosphate as well as lower calcium and haemoglobin in comparison with ERs. Hypertension, pulmonary oedema, fluid overload, treatment in the intensive care unit (ICU) and body mass index (BMI) below 10th percentile turned out to be more frequent in the LR group. Peritoneal dialysis (PD) was used as the first method of dialysis in 59% of ERs and 46% of LRs. The majority of ER patients was treated in the predialysis period with calcitriol, phosphate binders and low protein diet (84%, 89%, 92% of all children, respectively), and 20% of them received epoetin. In the up to 3 years observation of our initial cohort, we also found that the patients who were referred late were less likely to receive kidney transplant (P = 0.02). CONCLUSION: The results of the study indicate that the LR to a pediatric nephrologist was associated with poorer clinical and metabolic status of children entering chronic dialysis programmes.