PKD2-Related Autosomal Dominant Polycystic Kidney Disease: Prevalence, Clinical Presentation, Mutation Spectrum, and Prognosis.

BACKGROUND: PKD2-related autosomal dominant polycystic kidney disease (ADPKD) is widely acknowledged to be of milder severity than PKD1-related disease, but population-based studies depicting the exact burden of the disease are lacking. We aimed to revisit PKD2 prevalence, clinical presentation, mutation spectrum, and prognosis through the Genkyst cohort. STUDY DESIGN: Case series, January 2010 to March 2016. SETTINGS & PARTICIPANTS: Genkyst study participants are individuals older than 18 years from 22 nephrology centers from western France with a diagnosis of ADPKD based on Pei criteria or at least 10 bilateral kidney cysts in the absence of a familial history. Publicly available whole-exome sequencing data from the ExAC database were used to provide an estimate of the genetic prevalence of the disease. OUTCOMES: Molecular analysis of PKD1 and PKD2 genes. Renal survival, age- and sex-adjusted estimated glomerular filtration rate. RESULTS: The Genkyst cohort included 293 patients with PKD2 mutations (203 pedigrees). PKD2 patients with a nephrology follow-up corresponded to 0.63 (95% CI, 0.54-0.72)/10,000 in Brittany, while PKD2 genetic prevalence was calculated at 1.64 (95% CI, 1.10-3.51)/10,000 inhabitants in the European population. Median age at diagnosis was 42 years. Flank pain was reported in 38.9%; macroscopic hematuria, in 31.1%; and cyst infections, in 15.3% of patients. At age 60 years, the cumulative probability of end-stage renal disease (ESRD) was 9.8% (95% CI, 5.2%-14.4%), whereas the probability of hypertension was 75.2% (95% CI, 68.5%-81.9%). Although there was no sex influence on renal survival, men had lower kidney function than women. Nontruncating mutations (n=36) were associated with higher age-adjusted estimated glomerular filtration rates. Among the 18 patients with more severe outcomes (ESRD before age 60), 44% had associated conditions or nephropathies likely to account for the early progression to ESRD. LIMITATIONS: Younger patients and patients presenting with milder forms of PKD2-related disease may not be diagnosed or referred to nephrology centers. CONCLUSIONS: Patients with PKD2-related ADPKD typically present with mild disease. In case of accelerated degradation of kidney function, a concomitant nephropathy should be ruled out.

C3 nephritic factor associated with C3 glomerulopathy in children.

BACKGROUND: C3 glomerulopathy (C3G) is characterized by predominant C3 deposits in glomeruli and dysregulation of the alternative pathway of complement. Half of C3G patients have a C3 nephritic factor (C3NeF). C3G incorporated entities with a range of features on microscopy including dense deposit diseases (DDD) and C3 glomerulonephritis (C3GN). The aim of this work was to study children cases of C3G associated with C3NeF. METHODS: We reviewed 18 cases of C3G with a childhood onset associated with C3NeF without identified mutations in CFH, CFI, and MCP genes. RESULTS: Clinical histories started with recurrent hematuria for seven patients, nephrotic syndrome for four, acute post-infectious glomerulonephritis for three and acute renal failure for four. Twelve patients had a low C3 at first investigation. Kidney biopsy showed ten C3GN and eight DDD. Twenty-three percent of the patients tested presented elevated sC5b9. Seven patients relapsed 3 to 6 years after the onset. At the end of follow-up, two patients were under dialysis, 11 had a persistent proteinuria, five had none; four patients did not follow any treatment. Steroids were first used in 80 % of cases. CONCLUSIONS: C3NeF associated C3G has a heterogeneous presentation and outcome. Anti-proteinuric agents may control the disease during follow-up, even after nephrotic syndrome at the onset. The efficiency of immunosuppressive therapy remains questionable.

Mutations in complement C3 predispose to development of atypical hemolytic uremic syndrome.

Atypical hemolytic uremic syndrome (aHUS) is a disease of complement dysregulation. In approximately 50% of patients, mutations have been described in the genes encoding the complement regulators factor H, MCP, and factor I or the activator factor B. We report here mutations in the central component of the complement cascade, C3, in association with aHUS. We describe 9 novel C3 mutations in 14 aHUS patients with a persistently low serum C3 level. We have demonstrated that 5 of these mutations are gain-of-function and 2 are inactivating. This establishes C3 as a susceptibility factor for aHUS.

Mutations of NPHP2 and NPHP3 in infantile nephronophthisis.

Nephronophthisis is an autosomal recessive chronic tubulointerstitial disease that progresses to end-stage renal disease (ESRD) in about 10% of cases during infancy. Mutations in the INVS (NPHP2) gene were found in a few patients with infantile nephronophthisis. Mutations of NPHP3, known to be associated with adolescent nephronophthisis, were found in two patients with early-onset ESRD. Here we screened 43 families with infantile nephronophthisis (ESRD less than 5 years of age) for NPHP2 and NPHP3 mutations and determined genotype-phenotype correlations. In this cohort there were 16 families with NPHP2 mutations and NPHP3 mutations in seven. Three patients carried only one heterozygous mutation in NPHP3. ESRD arose during the first 2 years of life in 16 of 18 patients with mutations in NPHP2, but in only two patients with mutations in NPHP3. Renal morphology, characterized by hyper-echogenic kidneys on ultrasound and tubular lesions with interstitial fibrosis on histology, was similar in the two patient groups. The kidney sizes were highly diverse and ultrasound-visualized cysts were present in a minority of cases. Extra-renal anomalies were found in 80% of the entire cohort including hepatic involvement (50%), cardiac valve or septal defects (20%) and recurrent bronchial infections (18%). We show that NPHP3 mutations in both infantile and adolescent nephronophthisis point to a common pathophysiological mechanism despite their different clinical presentations.

[Effects of exercise training on ergocycle during hemodialysis in patients with end stage renal disease: relevance of the anaerobic threshold intensity]. / Effets d'un réentraînement à l'effort sur ergocycle pendant les séances de dialyse chez les insuffisants rénaux chroniques hémodialysés: intérêt d'un travail individualisé au premier seuil ventilatoire.

BACKGROUND: Chronic kidney failure (CRF) in addition to cardiovascular comorbidities and aging decrease physical activity capacity. An adapted rehabilitation program might be strongly recommended in this population. The aim of the study is to evaluate a 3 months exercise training program with ergocycle at the anaerobic threshold (AT) during dialysis sessions on effort tolerance, quality of life, blood pressure and lipidic disorders. METHODS: Six patients meanly aged 72 were evaluated before (t(0)) and after (t(3)) the rehabilitation program by: maximal cardiorespiratory ergotest, a 6-Minute Walk Test (6MWT) and 2 quality of life tests: Medical Outcome Survey Short Form 36-items and the Kidney Disease Quality of Life (SF 36, KDQol). RESULTS: Physical activity during dialysis is well tolerated. There was no undesirable event during rehabilitation sessions. The dyspnea and muscular weariness threshold linked to the AT increased meanly by 39% (8.83 ± 0.87 vs. 12.25 ± 1.23 mL/min per kg). Distances walked during 6 MWT increased for all patients (351.83 ± 72.17 vs. 412.80 ± 82 meters) Moreover, physical component scale improved (+4.7), mean systolic blood pressure (-7 mmHg) and mean triglycerides concentration (-19%) decreased. CONCLUSION: An exercise training program during dialysis sessions with ergocycle and working intensity based on AT seems safe and an effective alternative to improve the effort functional capacity by hemodialysis patients.

Differential impact of complement mutations on clinical characteristics in atypical hemolytic uremic syndrome.

Mutations in factor H (CFH), factor I (IF), and membrane cofactor protein (MCP) genes have been described as risk factors for atypical hemolytic uremic syndrome (aHUS). This study analyzed the impact of complement mutations on the outcome of 46 children with aHUS. A total of 52% of patients had mutations in one or two of known susceptibility factors (22, 13, and 15% of patients with CFH, IF, or MCP mutations, respectively; 2% with CFH+IF mutations). Age <3 mo at onset seems to be characteristic of CFH and IF mutation-associated aHUS. The most severe prognosis was in the CFH mutation group, 60% of whom reached ESRD or died within <1 yr. Only 30% of CFH mutations were localized in SCR20. MCP mutation-associated HUS has a relapsing course, but none of the children reached ESRD at 1 yr. Half of patients with IF mutation had a rapid evolution to ESRD, and half recovered. Plasmatherapy seemed to have a beneficial effect in one third of patients from all groups except for the MCP mutation group. Only eight (33%) of 24 kidney transplantations that were performed in 15 patients were successful. Graft failures were due to early graft thrombosis (50%) or HUS recurrence. In conclusion, outcome of HUS in patients with CFH mutation is catastrophic, and posttransplantation outcome is poor in all groups except for the MCP mutation group. New therapies are urgently needed, and further research should elucidate the unexplained HUS group.

Central neurotoxicity of cyclosporine in two children with nephrotic syndrome.

The central neurotoxicity of cyclosporin A (CsA) has been abundantly documented in pediatric and adult recipients of bone marrow or organ transplants, with variations in the rate of occurrence from 0.5% to 35%. We report two cases of central neurotoxicity ascribable to CsA in children with nephrotic syndrome due to lipoid nephrosis. The manifestations of CsA-related central neurotoxicity include confusion, aphasia, dystonias, akinetic mutism, parkinsonism, palsies, seizures, catatonia, coma, brain hemorrhage, and cortical blindness. Decreased density of the cerebral white matter is visible by computed tomography (CT) in 50% of cases, with the most commonly involved sites being the occipital cortex, the cerebellum, the periventricular substance, and the brainstem. Magnetic resonance imaging is more sensitive and more specific than CT for investigating the white matter. High-signal lesions are seen on T2-weighted sequences in the areas that are abnormal by CT. Many risk factors have been reported, including hypomagnesemia, hypocholesterolemia, high-dose glucocorticoid therapy, arterial hypertension, and infections. We present two patients with central neurotoxicity both of whom have elevated cholesterol levels.