Anne-Laure Sellier-Leclerc

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.

Rituximab in steroid-dependent idiopathic nephrotic syndrome in childhood—follow-up after CD19 recovery

Rituximab (RTX) is a new treatment strategy in high-degree steroid-dependent idiopathic nephrotic syndrome (SDNS) in childhood. Thirty patients (nine girls) with SDNS with steroid side effects and previously treated with immunosuppressive drugs, mostly calcineurin inhibitors, were treated with RTX and included in this non-controlled single-centre study. Patient age at first RTX infusion was 12.9 ± 0.7 years. Our aim was to evaluate disease outcome after a minimum CD19 depletion period of 15 months obtained by repeated RTX infusion. Minimum follow-up after initial CD19 depletion was 24 months. During the RTX treatment period, seven patients had nephrotic syndrome relapses, six among them at the time of an intermittent CD19 recovery and one patient relapsed under CD19 depletion. The risk for these patients to relapse after the RTX treatment period was higher than in those without intermittent relapses. After definitive CD19 recovery over a follow-up of 17.4 ± 1.9 months, 19 patients (63%) did not relapse and 11 (37%) relapsed 4.3 ± 1 months after defininitive CD19 recovery. Among these 11 patients, 6 already had intermittent relapses during the RTX treatment period. Steroid and immunosuppressive treatment could be discontinued in all patients during CD19 depletion and was re-introduced in two after CD19 recovery. Fourteen patients had mostly benign and transitory side effects, which did not require RTX discontinuation. In conclusion, RTX treatment with a 15-month CD19 depletion period induced long-term remission after definitive CD 19 recovery in almost two-thirds the of patients without oral immunosuppressive drugs.

Plasmatherapy in atypical hemolytic uremic syndrome.

Plasmatherapy has become empirically first-line treatment in atypical hemolytic uremic syndrome (aHUS), although no prospective controlled trials have been conducted. Patients with mutations that induce complete or partial factor H (FH) quantitative deficiency may be controlled by plasma infusions (PI), but plasma exchanges appear more efficient than PI in patients with mutations that result in a mutant dysfunctional FH in the circulation. Early treatment is crucial. Long-term prophylactic plasmatherapy appears more efficient to prevent end-stage renal disease (ESRD) than plasmatherapy only during relapses. However, the longest follow-up with preserved renal function under plasmatherapy is only 6.5 years. Plasmatherapy does not appear to influence the outcome of aHUS with membrane cofactor protein mutation, and its efficacy in patients with factor I, C3, or factor B mutations is suggested by a few reports. We hope complement blockers will offer patients a better chance to avoid ESRD and provide a better quality of life.

A Humanized Mouse Model of Idiopathic Nephrotic Syndrome Suggests a Pathogenic Role for Immature Cells

Idiopathic nephrotic syndrome is characterized by glomerular proteinuria in the absence of infiltrating cells or immunoglobulin deposits. Although it is suspected that T cells secrete a circulating factor that leads to proteinuria by altering the permeability of the glomerular filtration barrier, the precise etiology of this syndrome is unknown. Because an animal model that mimics human idiopathic nephrotic syndrome does not exist, we developed a humanized mouse model of the disease by injecting CD34(+) stem cells or CD34(-) peripheral blood mononuclear cells from afflicted patients into immunocompromised mice. Even though both CD34(+) and CD34(-) cells induced the engraftment of human CD45(+) leukocytes in mice, only the injection of CD34(+) stem cells induced albuminuria. Ultrastructural analysis of glomeruli from the resulting proteinuric mice revealed effacement of podocyte foot processes, similar to the pathology observed in the human disease. Therefore, our data suggest that the cells responsible for the pathogenesis of idiopathic nephrotic syndrome are more likely to be immature differentiating cells rather than mature peripheral T cells.

Fulminant viral myocarditis after rituximab therapy in pediatric nephrotic syndrome

BackgroundWe report a 7-year-old boy with high-degree steroid-dependent idiopathic nephrotic syndrome (SDNS) who went into remission with rituximab (RTX) maintenance therapy.Case-Diagnosis/TreatmentFour months after this patient received his first RTX infusion, there was a progressive and sustained decrease of immunoglobulin (Ig)G and IgM levels. Thirteen months after the initiation of RTX therapy he was in sustained remission without any steroid or oral immunosuppressive therapy; however, B cell depletion was still present. At this time he developed a fulminant myocarditis due to enterovirus. Despite aggressive treatment and the administration of intravenous polyvalent immunoglobulins there was no clinical improvement. He successfully underwent heart transplant surgery.ConclusionsWe conclude that B cell depletion with RTX is efficacious in the treatment of paediatric SDNS but that it may be associated with severe infectious complications. Therefore, we recommend a close monitoring of Ig levels in children who have received RTX therapy and a supplementation with intravenous Ig as soon as the Ig levels fall below the lower limit of the normal range

Acute tubulointerstitial nephritis

Acute tubulointerstitial nephritis (TIN) is a frequent cause of acute renal failure, characterised by the presence of inflammatory cell infiltrate in the interstitium of the kidney. Immuno-allergic reaction to certain medications, mainly non-steroidal anti-inflammatory drugs and antibiotics are by far the most important etiology for TIN today, but other situations such as infections, toxins, and vasculitis are known to induce TIN. Incidence of TIN is increasing, probably due to prescription habits and NSAID overuse, representing 3–7% of acute kidney injury in biopsies in children. Avoidance of the causal substance and rapid steroid therapy are hallmarks for patient care, but spontaneous initial recovery is very frequent and the general prognosis seems satisfactory. However, development of chronic TIN, without response to steroid or other immunosuppressive treatment, is possible. As the largest part of TIN is secondary to certain drugs, clear indications in particular for NSAID or antibiotics should be respected to reduce the number of TIN cases.

Eculizumab in neonatal hemolytic uremic syndrome with homozygous factor H deficiency

BackgroundNeonatal atypical hemolytic uremic syndrome (aHUS) is a rare but severe disease that is mainly due to methylmalonic aciduria or genetic complement abnormalities. Traditional management of aHUS includes plasma infusion/exchange, but in small or unstable infants, plasma exchange can be challenging because of high extracorporeal volume and difficulty to obtain an adequate venous access. The C5 complement blocker eculizumab has become a cornerstone of first-line management of aHUS due to complement deregulation in older patients. However, little data are available on its use in neonatal aHUS.Case-diagnosis/treatmentWe report on an 11-day-old neonate with severe aHUS (myocardial impairment, respiratory failure, acute kidney disease requiring hemodiafiltration) due to homozygous factor-H deficiency. She received early treatment with eculizumab as first-line therapy and completely recovered within 5 days. A second dose of eculizumab was administered 7 days after the first infusion, followed by a dose every 2 weeks for 2 months and then every 3 weeks, at the same dosage (300 mg). With more than 24 months of follow-up, renal function remains normal.ConclusionsWe report on the long-term efficacy and safety of eculizumab as first-line therapy in neonatal aHUS. However its use still requires optimization in terms of indications and administration (frequency, dosage).

Childhood onset diabetes posttransplant in a girl with TCF2 mutation

Heterozygous mutations of TCF2 (transcription factor 2) have been associated with maturity onset diabetes of the young, renal malformations, hyperuricemia, and occasionally internal genital malformations in female. We report a female patient with bilateral renal hypodysplasia and de novo heterozygous TCF2 gene mutation. At the age of 9 yr, she developed transient ketoacidosis immediately posttransplant, temporarily requiring insulin. During glucocorticoid tapering, impaired glucose tolerance persisted and overt insulin‐dependent diabetes mellitus developed 1 yr later. Pathogenic factors which might have played a role in the acceleration of diabetes were (i) switch from cyclosporine to tacrolimus, (ii) weight excess, and (iii) cytomegalovirus infection. TCF2 analysis might, therefore, be of interest in patients with congenital abnormalities of the kidney and the urinary tract in order to improve posttransplant management in terms of steroid and tacrolimus exposure.

Patterns of Clinical Response to Eculizumab in Patients With C3 Glomerulopathy

BACKGROUND Cases reports and small series of patients with C3 glomerulopathy have reported variable efficacy of eculizumab. STUDY DESIGN Case series of C3 glomerulopathy. SETTING & PARTICIPANTS Pediatric and adult patients with C3 glomerulopathy treated with eculizumab between 2010 and 2016 were identified through the C3 glomerulopathy French registry database, and a questionnaire was sent to participating French pediatric and adult nephrology centers, as well as one pediatric referral center in Québec, Canada. OUTCOMES Global or partial clinical renal response. MEASUREMENTS Evolution of serum creatinine and proteinuria values. RESULTS 26 patients (13 children/adolescents) were included. 22 (85%) patients had received steroids, plasma exchange, or immunosuppressive therapy before eculizumab, and 3 of them had rapid progression of their kidney disease despite treatment. At the initiation of eculizumab therapy, 11 (42%) patients had chronic kidney disease, 7 (27%) had rapidly progressive disease, and 3 (12%) required dialysis. After eculizumab treatment (median duration, 14 months), 6 (23%) patients had a global clinical response; 6 (23%), a partial clinical response; and 14 (54%), no response. Compared with those who had a partial clinical or no response, patients who had a global clinical response had lower estimated glomerular filtration rates, a more rapidly progressive course, and more extracapillary proliferation on kidney biopsy. Age, extent of renal fibrosis, frequency of nephrotic syndrome, low serum C3 and C3 nephritic factor and elevated soluble C5b-9 concentrations, or complement gene variants did not differ between responders and nonresponders. LIMITATIONS Retrospective design without a control group, relatively small number of cases, inclusion of pediatric and adult cases. CONCLUSIONS Eculizumab appears to be a potential treatment for patients with crescentic rapidly progressive C3 glomerulopathy. Its benefit in patients with non-rapidly progressing forms seems to be limited.

Eculizumab treatment in severe pediatric STEC-HUS: a multicenter retrospective study.

BackgroundHemolytic uremic syndrome related to Shiga-toxin-secreting Escherichia coli infection (STEC-HUS) remains a common cause of acute kidney injury in young children. No specific treatment has been validated for this severe disease. Recently, experimental studies highlight the potential role of complement in STEC-HUS pathophysiology. Eculizumab (EC), a monoclonal antibody against terminal complement complex, has been used in severe STEC-HUS patients, mostly during the 2011 German outbreak, with conflicting results.MethodsOn behalf of the French Society of Pediatric Nephrology, we retrospectively studied 33 children from 15 centers treated with EC for severe STEC-HUS. Indication for EC was neurologic involvement in 20 patients, cardiac and neurologic involvement in 8, cardiac involvement in 2, and digestive involvement in 3. Based on medical status at last follow-up, patients were divided into two groups: favorable (n = 15) and unfavorable outcomes (n = 18).ResultsAmong patients with favorable outcome, 11/14 patients (79%) displayed persistent blockade of complement activity before each EC reinjection. Conversely, in patients with unfavorable outcome, only 9/15 (53%) had persistent blockade (p = n.s.). Among 28 patients presenting neurological symptoms, 19 had favorable neurological outcome including 17 with prompt recovery following first EC injection. Only two adverse effects potentially related to EC treatment were reported.ConclusionsTaken together, these results may support EC use in severe STEC-HUS patients, especially those presenting severe neurological symptoms. The study, however, is limited by absence of a control group and use of multiple therapeutic interventions in treatment groups. Thus, prospective, controlled trials should be undertaken.