Effect of cyclosporin A on glomerular filtration rate in children with minimal change nephrotic syndrome

Role of cathepsin L in idiopathic nephrotic syndrome in children

Nephrotic syndrome (NS) is one of the most common glomerular diseases in children. Glomerular podocyte dysfunction can result in proteinuria, the presence of a large amount of protein in the urine. Podocytes are unique epithelial cells that divide into 3 separate structural and functional segments: a cell body, major processes, and foot processes. Since synaptopodin, dynamin, and actin are crucial components of the podocyte cytoskeleton, degradation of these proteins is associated with cytoskeleton instability, resulting in the development of proteinuria. Cathepsin L (CatL), a cysteine proteinase, plays a crucial role in various renal diseases. CatL expression is elevated in rats with puromycin aminonucleoside-induced nephropathy, which is used as a model of minimal change NS. In CatL-deficient mice, which do not develop proteinuria, dynamin is retained through the escape of CatL-mediated decomposition, resulting in no changes in the filtration barrier of podocytes. However, there is limited information on the roles of CatL in NS. Based on these data, CatL might play an important role in the development of proteinuria. Furthermore, identifying the functions of CatL may contribute to a better understanding of the pathogenesis of childhood-onset NS. We hypothesize that high levels of CatL can lead to cytoskeletal instability of podocytes, resulting in proteinuria in childhood-onset NS.

Infrequent tacrolimus-induced nephrotoxicity in French patients with steroid-dependent nephrotic syndrome

BACKGROUND

Chronic nephrotoxicity with potentially irreversible lesions is a major concern regarding calcineurin inhibitor (CNI) treatment in children with severe forms of idiopathic nephrotic syndrome (INS).

CASE-DIAGNOSIS/TREATMENT

We retrospectively included all children on CNI for steroid-dependent INS with a duration of CNI treatment of more than 1 year. Only patients in whom CNI could not be replaced by mycophenolate mofetil were included. All included patients underwent a kidney biopsy. All results were expressed as median and range. Twenty-one children (6 girls) were included. Age at disease onset was 49 (29-66) months and treatment duration on CNI was 30 (20-45) months. Age at kidney biopsy was 108 (78-170) months. Number of relapses was 7 (3-9) since disease onset. Serum creatinine level was transiently and moderately increased in two patients. Kidney biopsy revealed minimal change disease in 20/21 patients and focal segmental glomerulosclerosis in 1/21. Evidence for chronic CNI nephrotoxicity was found in one patient revealed by arteriolar hyalinosis and fibrosis in 50% of glomeruli.

CONCLUSIONS

CNI-induced chronic nephrotoxicity was infrequent. In patients who require long-term and/or high-dose CNI treatment, kidney biopsies might be useful to exclude chronic CNI-induced lesions.

Pathogenesis and Management of Acute Kidney Injury in Patients with Nephrotic Syndrome Due to Primary Glomerulopathies

Acute kidney injury in the context of nephrotic syndrome is a serious and alarming clinical problem. Largely, acute kidney injury is a relatively frequent complication among patients with comorbidities while it has been independently associated with an increased risk of adverse outcomes, including death and chronic kidney disease. Nephrotic syndrome, without hematuria or with minimal hematuria, includes a list of certain glomerulopathies; minimal change disease, focal segmental glomerulosclerosis and membranous nephropathy. In the light of primary nephrotic syndrome, pathophysiology of acute kidney injury is differentiated by the nature of the primary disease and the severity of the nephrotic state. This review aims to explore the clinical circumstances and pathogenetic mechanisms of acute kidney injury in patients with nephrotic syndrome due to primary glomerulopathies, focusing on newer perceptions regarding the pathogenesis and management of this complicated condition, for the prompt recognition and timely initiation of appropriate treatment in order to restore renal function to its baseline level. Prompt recognition of the precise cause of acute kidney injury is crucial for renal recovery. Clinical characteristics, laboratory and serological findings along with histopathological findings, if required, will reveal the implicated pathway leading to individualized approach and management.

Calcineurin inhibitor induced nephrotoxicity in steroid resistant nephrotic syndrome

Prolonged therapy with calcineurin inhibitors (CNI) is effective in patients with difficult nephrotic syndrome. However, information on prevalence and risk factors for nephrotoxicity in children with steroid-resistant nephrotic syndrome is limited. This retrospective observational study was conducted on 40 patients with steroid-resistant nephrotic syndrome treated with cyclosporine (CyA) (n = 28) or tacrolimus (n = 12) for more than 2 years. Nephrotoxicity was defined by the presence of striped fibrosis involving ≥10% of the interstitium or nodular hyalinosis in more than one arteriole. Ten additional parameters were graded semi-quantitatively. Continuous data are presented as median and interquartile range (IQR). The median (IQR) age at onset of nephrotic syndrome and CNI therapy were 30 (21-45) and 49.5 (40-102.5) months. A second renal biopsy, following 30 (26-35) months of CNI therapy, showed histological toxicity in 10 (25%) patients. Toxicity was seen in 7 and 3 patients receiving CyA and tacrolimus, respectively, and 5 patients each with minimal change and focal segmental glomerulosclerosis. Therapy with CNI was associated with significant increases in scores for global glomerulosclerosis, tubular atrophy, interstitial fibrosis, nonnodular arteriolar hyalinosis (P < –0.001 for all), arteriolar smooth-muscle vacuolization (P = –0.02), juxtaglomerular hyperplasia (P = –0.002), and tubular microcalcinosis (P = –0.06). Risk factors for nephrotoxicity were initial resistance (OR 9; 95% CI 1.0-80.1; P = –0.049); dose of CyA (OR 9.2; 95% CI 1.1-74.6; P = –0.037); duration of heavy proteinuria (OR 1.2; 95% CI 1.0-1.4; P = –0.023); and hypertension during therapy (OR 6; 95% CI 1.3-28.3; P = –0.023). Following prolonged CNI therapy, one in four biopsies show features of toxicity. Prolonged duration of heavy proteinuria, hypertension, initial steroid resistance and high CyA dose predict the occurrence of nephrotoxicity.

Second-line options for refractory steroid-sensitive and -resistant nephrotic syndrome

Although initially, many children with idiopathic nephrotic syndrome respond to steroid therapy, a repeated course for patients with relapses often causes significant steroid toxicity. Patients with frequent relapses or steroid dependency thus require alternative treatment, and so far, cyclophosphamide or levamisole have been regarded as first-choice options, although the latter is no longer available in many countries. Data are accumulating that mycophenolic acid may be an alternative for these patients. Calcineurin inhibitors (cyclosporine A or tacrolimus) are usually effective and are often used after cytotoxic treatment, but long-term treatment is necessary, raising concerns regarding the accumulation of side effects. Still, some patients show a tendency to relapse even on this maintenance regimen and some even have a refractory course that creates a medical dilemma. For this situation, recent data have demonstrated an effect of monoclonal antibodies directed to B cells - rituximab, a drug that may also prove to be a therapeutic option in less complicated cases. Patients that do not respond to initial steroid treatment need genetic testing and a renal biopsy, since focal segmental glomerulosclerosis may be present. Treatment options include pulse methylprednisolone, often in addition to calcineurin inhibitors (mainly cyclosporine but also, recently, tacrolimus). Cyctotoxic treatment, especially intravenous cyclophosphamide, has been found to be effective in steroid-resistant nephrotic syndrome by some studies but is inferior to calcineurin inhibitors. In addition, mycophenolic acid and rituximab have been used in children with primary focal segmental glomerulosclerosis; however, response seems to be inferior in comparison with patients with steroid-sensitive nephrotic syndrome. Taken together, idiopathic nephrotic syndrome, including steroid-sensitive as well as steroid-resistant patients, is a potentially serious disorder. Although much progress has been made in recent years and a wide arsenal of immunological interventions is available, some patients have a treatment refractory course. Prospective studies or at least standardization of treatment for complicated cases is urgently needed.

Management patterns of childhood-onset nephrotic syndrome

As an initial effort to identify opportunities to improve the management of children with nephrotic syndrome, the goal of this study was to assess the present-day management of children with primary nephrotic syndrome. A web-based survey was designed to assess the current management styles of all pediatric nephrology faculties at ten participating institutions. Ninety-one percent completed the initial survey. The duration of initial glucocorticoid therapy ranged from 4 to 24 weeks. Physicians reported that the recommendation for kidney biopsy was dependent on the response to initial corticosteroid therapy, with the minority always recommending a biopsy for frequently relapsing or steroid-dependent cases. All responding physicians recommended a kidney biopsy in steroid-resistant cases. Treatment strategies were reported to vary based upon the steroid response pattern and, where available, kidney histopathology. Striking variations in therapeutic preferences were described when alternatives to glucocorticoids were considered. The variability of management practices among pediatric nephrologists in the USA combined with the changing characteristics of our pediatric population raise concerns about our future strategies for improving healthcare for children coping with nephrotic syndrome. This variability is not unique to children's healthcare or to nephrology. However, a systematic approach to patient care and improvement in health outcomes has been shown to substantially improve morbidity and mortality outcomes in children with chronic health conditions.

Management of childhood onset nephrotic syndrome

The therapeutic approach to childhood nephrotic syndrome is based on a series of studies that began with an international collaborative effort sponsored by the International Study of Kidney Disease in Children in 1967. The characteristics of children presenting with nephrotic syndrome have changed over recent decades with greater frequency of the challenging condition focal segmental glomerulosclerosis and a greater prevalence of obesity and diabetes mellitus, which may be resistant to glucocorticoids in the former and exacerbated by long-term glucocorticoid therapy in the latter 2 conditions. The Children's Nephrotic Syndrome Consensus Conference was formed to systematically review the published literature and generate a children's primary nephrotic syndrome guideline for use in educational, therapeutic, and research venues.

Experience with tacrolimus in children with steroid-resistant nephrotic syndrome

Children with steroid-resistant nephrotic syndrome (SRNS) are at risk of developing renal failure. We report here the results of a single-center retrospective observational study of the remission rate in pediatric patients with SNRS receiving tacrolimus. Serial renal biopsies from children on tacrolimus therapy were evaluated for tubulointerstitial fibrosis and transforming growth factor-beta immunostaining. Of the 16 children with SRNS, 15 went into complete remission after a median of 120 days of therapy. Nine children were able to stop steroids, while the others were on tapering doses. Forty-seven percent had relapses, most of which were steroid-responsive. Serial renal biopsies were obtained from seven children after a median treatment duration of 24 months; two of these children had increased tubulointerstitial fibrosis and four showed increased transforming growth factor-beta tissue staining. Children with worsening histological findings were younger. There was no significant association between tacrolimus exposure and biopsy changes, although the average trough level was higher in those children with worsening histological findings. In conclusion, tacrolimus may be a safe and effective alternative agent for inducing remission in children with SRNS. However, caution needs to be taken when prescribing this agent due to its narrow therapeutic index. Serial renal biopsies are necessary to check for subclinical nephrotoxicity, especially in younger children and those with higher trough levels.

Mycophenolate mofetil versus cyclosporine for remission maintenance in nephrotic syndrome

We performed a multi-centre randomized controlled trial to compare the efficacy of mycophenolate mofetil (MMF) to that of cyclosporine A (CsA) in treating children with frequently relapsing nephrotic syndrome and biopsy-proven minimal change disease. Of the 31 randomized initially selected patients, seven were excluded. The remaining 24 children received either MMF 1200 mg/m(2) per day (n = 12) or CsA 4-5 mg/kg per day (n = 12) during a 12-month period. Of the 12 patients in the MMF group, two discontinued the study medication. Evaluation of the changes from the baseline glomerular filtration rate showed an overall significant difference in favour of MMF over the treatment period (p = 0.03). Seven of the 12 patients in the MMF group and 11 of the 12 patients in the CsA group remained in complete remission during the entire study period. Relapse rate in the MMF group was 0.83/year compared to 0.08/year in the CsA group (p = 0.08). None of the patients reported diarrhea. Pharmacokinetic profiles of mycophenolic acid were performed in seven patients. The patient with the lowest area under the curve had three relapses within 6 months. In children with frequently relapsing minimal change nephrotic syndrome, MMF has a favourable side effect profile compared to CsA; however, there is a tendency towards a higher relapse risk in patients treated with MMF.

Cyclosporine-A-induced nephrotoxicity in children with minimal-change nephrotic syndrome: long-term treatment up to 10 years

The impact of cyclosporine A (CsA) therapy in patients with steroid-dependent nephrotic-syndrome (SDNS) on long-term renal function is controversial. Data beyond 5 years are rare. Long-term renal function was evaluated in children with SDNS with and without CsA therapy, especially beyond 5 years. Twenty children were treated with CsA (study group) for a mean of 5.4 +/- 2.2 years (ten patients for 5-11 years). Glomerular filtration rate (GFR) was calculated before and after 3 and 12 months and at latest follow-up of therapy. Fifteen children with cyclophosphamide-treated SDNS without CsA served as controls. In the study group, GFR decreased within 12 months from 136 +/- 19 to 120 +/- 31, to 114 +/- 14 ml/min per 1.73 m(2) at latest follow-up (p < 0.0001). Patients with CsA > 5 years had a GFR of 111 +/- 14 ml/min per 1.73 m(2) at latest follow-up without a GFR below 90 ml/min per 1.73 m(2). No CsA toxicity was found in biopsies. In the control group, GFR dropped within 3 months, from 137 +/- 27 to 130 +/- 24, to 126 +/- 19 ml/min per 1.73 m(2) at latest follow-up (p = 0.1). Patients with and without nephrotoxic CsA therapy showed a drop in GFR. In CsA-treated patients, GFR was about 12% lower at latest follow-up compared with patients without nephrotoxic therapy but always remained within normal range. CsA seems to be safe, even in long-term treatment for more than 5 years.

Initial treatment of idiopathic nephrotic syndrome in children: prednisone versus prednisone plus cyclosporine A: a prospective, randomized trial

Previous studies of the Arbeitsgemeinschaft für Pädiatrische Nephrologie in children with steroid-sensitive nephrotic syndrome have shown that the length of initial prednisone therapy has an impact on the subsequent relapse rate. The aim of this randomized, prospective, multicenter study was to reduce the number of relapses further by increasing the initial immunosuppression: Patients with an initial attack of nephrotic syndrome were randomly allocated to treatment with 6 wk of 60 mg/m(2) per d prednisone followed by 6 wk of 40 mg/m(2) per 48 h (Pred group) or to the same prednisone treatment plus 8 wk of cyclosporine (Pred+CsA group). The primary end point was first relapse; follow-up was truncated at 2 yr. In the Pred+CsA group (n = 49 patients), the first relapse occurred later compared with the Pred group (n = 55 patients) (median 22.8 versus 12.5 mo). After 6 mo, 10.4% of patients in the Pred+CsA group experienced a first relapse versus 31.5% in the Pred group (P = 0.01); after 1 yr, 36.5 versus 51% (P = 0.15); and after 2 yr, 51 versus 50%. The mean relapse rate per patient was 0.12 versus 0.57 after 6 mo (P = 0.01), 0.63 versus 1.03 after 1 yr (P = 0.02), and 1.03 versus 2.06 after 2 yr (not significant). The significant benefit for adding CsA was lost after 9 to 12 mo. GFR remained unchanged. The subsequent treatment rate with cyclophosphamide was lower in the CsA group (five versus 12 patients) after 2 yr. With the use of logistic regression statistics, children who were younger than 7 yr show a significantly better sustained remission rate with initial CsA treatment for the 2-yr observation time (P = 0.03). It remains questionable, however, whether the intensified initial treatment with CsA could be recommended generally.

Management of the difficult nephrotic patient

Most children with nephrotic syndrome do well, usually with multiple relapses and remissions. Some children require high doses of oral steroids to sustain a remission and develop significant steroid toxicity. These patients frequently can be managed with oral alkylating agents or with cyclosporine. A few nephrotic children to not respond to oral prednisone. The most common biopsy finding in steroid-resistant patients is focal segmental glomerulosclerosis. Many patients with this condition progress to chronic renal failure. Evidence suggests that the outcome is improved with either cyclosporine or with a protocol using pulse intravenous methylprednisolone and oral alkylating agents.

Alternative treatment to corticosteroids in steroid sensitive idiopathic nephrotic syndrome

A review was undertaken of the use of alternative immunosuppressive treatment in addition to corticosteroids in a cohort of 429 children with steroid sensitive nephrotic syndrome (SSNS) treated between 1980 and 1994. Two hundred and twenty two children (52%) received at least one course of alternative treatment, 98 (23%) two, and 43 (10%) three. Cyclophosphamide was administered to 196 children (46%); in 181 it was the first course of alternative treatment and in 104 (57%) of those it was also the last ('final course'). Levamisole was given to 56 children (13%) and cyclosporin to 53 (12%). Fifteen children in whom cyclosporin failed were treated with chlorambucil. A few patients received azathioprine or vincristine. Ten children developed secondary steroid resistance, of whom five progressed to chronic renal failure. Acute complications included reversible renal failure, septicaemia, peritonitis, convulsions, and cerebral thrombosis. There were three deaths. It is concluded that half of the referred children with SSNS were deemed to require at least one course of alternative immunosuppressive treatment, and that side effects of the treatment and complications of SSNS are infrequent but occasionally fatal.

Long-term cyclosporin A treatment of minimal-change nephrotic syndrome of childhood

We evaluated the efficacy of long-term cyclosporin A (CyA) treatment in the maintenance of remission in 40 children with steroid-dependent minimal-change nephrotic syndrome (MCNS). CyA was given in an initial dose of 5 mg/kg per day, adjusted to maintain a trough whole blood level of 50-150 ng/ml. All the 40 children received CyA for 1 year. In 18 patients, CyA was continued for a further period of at least a year without interruption; 9 patients had a second course of CyA therapy after an interval of at least 1 month. Of the 40 children 29 (72%) had one or more relapses during treatment with CyA, with 16 (40%) relapsing during the 1st year. During the second period of CyA, 10 (56%) of the 18 children treated continuously relapsed, whereas all the 9 children who had an interrupted course of therapy relapsed. CyA was discontinued at one time in 27 patients, all of whom subsequently relapsed, with a median time to relapse of 26 days. Long-term prednisolone in addition to CyA was required to maintain remission in 16 (40%) of the whole group. The results suggest that the long-term use of CyA is able to maintain remission of MCNS, although 40% of the patients also required low-dose alternate-day steroids; patients appeared to fare worse if the CyA course was interrupted; no patient experienced a long-term remission after CyA was stopped.