SummaryBackground and objectives This study evaluated the relevance of complement factor H (CFH)-related protein (CFHR) 1 deficiency in pediatric patients with atypical hemolytic uremic syndrome (aHUS) by evaluating both the frequency of deletions in CFHR1 and the presence of complement factor H (CFH) antibodies.Design, setting, participants, & measurements A total of 116 patients (mainly from central Europe) and 118 healthy blood donors were included from 2001 to 2012. The presence of CFHR1 gene deletions was determined in 90 pediatric patients with aHUS and 118 controls by an easy, fast, and cheap PCR assay; 100 patients with aHUS and 42 controls were tested for CFH antibodies by ELISA. Questionnaires were administered to evaluate the clinical and laboratory data.Results Homozygous deletion in CFHR1 was detected in 32% of the patients with aHUS tested, compared with 2.5% of controls (P,0.001). CFH antibodies were present in 25% of the patients and none of the controls. CFH antibodies were detected in 82% of patients with homozygous CFHR1 gene deletion and in 6% of patients without. CFH antibody-positive patients with aHUS showed a significantly lower platelet nadir at disease onset and significantly less frequent involvement of the central nervous system than did antibody-negative patients. Antibody-positive patients also received plasma therapy more often.Conclusion Homozygous deletion in CFHR1 is strongly associated with occurrence of CFH antibodies in pediatric patients with aHUS. However, despite this apparent genetic disease predisposition, it cannot be considered an exclusive cause for aHUS. Initial presentation of Shiga toxin-negative HUS with severe thrombocytopenia and no central nervous system complications in pediatric patients is especially suspicious for CFH antibody aHUS.

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Steroid-resistant focal segmental glomerulosclerosis (FSGS) often recurs after renal transplantation. In this international survey, we sought to identify genotype-phenotype correlations of recurrent FSGS. We surveyed 83 patients with childhood-onset primary FSGS who received at least one renal allograft and analyzed 53 of these patients for NPHS2 mutations. The mean age at diagnosis was 6.7 years, and the mean age at first renal transplantation was 13 years. FSGS recurred in 30 patients (36%) after a median of 13 days (range, 1.5 to 152 days). Twenty-three patients received a second kidney transplant, and FSGS recurred in 11 (48%) after a median of 16 days (range, 2.7 to 66 days). None of the 11 patients with homozygous or compound heterozygous NPHS2 mutations developed recurrent FSGS compared with 45% of patients without mutations. These data suggest that genetic testing for pathogenic mutations may be important for prognosis and treatment of FSGS both before and after transplantation.

Objective: To identify risk factors associated with mortality in critically ill children requiring continuous renal replacement therapy. Design: Retrospective observational study based on a prospective registry. Setting: Tertiary and quaternary referral 30-bed PICU. Patients: Critically ill children undergoing continuous renal replacement therapy were included in the study. Interventions: Continuous renal replacement therapy. Measurements and Main Results: Overall mortality was 36% (n = 58) among the 161 patients treated with continuous renal replacement therapy during the study period and was significantly higher in patients on extracorporeal membrane oxygenation (47.5%, 28 of 59) than in patients not requiring extracorporeal membrane oxygenation (28.4%, 29 of 102; p = 0.022). According to the admission diagnosis, we found the highest mortality in patients with onco-hematologic disease (77.8%) and the lowest in patients with renal disease (5.6%). Based on multivariate logistic regression analysis, the presence of higher severity of illness score at admission (adjusted odds ratio, 1.49; 95% CI, 1.18–1.89; p < 0.001), onco-hematologic disease (odds ratio, 17.10; 95% CI, 4.10–72.17; p < 0.001), fluid overload 10%–20% (odds ratio, 3.83; 95% CI, 1.33–11.07; p = 0.013), greater than 20% (odds ratio, 15.03; 95% CI, 4.03–56.05; p < 0.001), and timing of initiation of continuous renal replacement therapy (odds ratio, 1.01; 95% CI, 1.00–1.01; p = 0.040) were independently associated with mortality. In our population, the odds of dying increases by 1% for every hour of delay in continuous renal replacement therapy initiation from ICU admission. Conclusions: Mortality in children requiring continuous renal replacement therapy remains high and seems to be related to the underlying disease, the severity of illness, and the degree of fluid overload. In critically ill children at high risk for developing acute kidney injury and fluid overload, earlier initiation of continuous renal replacement therapy might result in decreased mortality.