Precise clinicopathologic findings for application of genetic testing in pediatric kidney transplant recipients with focal segmental glomerulosclerosis/steroid-resistant nephrotic syndrome.

BACKGROUND: Establishing a molecular genetic diagnosis of focal segmental glomerulosclerosis (FSGS)/steroid-resistant nephrotic syndrome (SRNS) can be useful for predicting post-transplant recurrence. Monogenic causes are reportedly present in approximately 20-30% of patients with FSGS/SRNS. However, the characteristics of patients who are likely to have a monogenic cause remain to be determined. METHODS: Pediatric recipients with SRNS and/or biopsy-proven FSGS who underwent their first kidney transplantation at our center between 1999 and 2019 were analyzed. Patients with secondary FSGS/SRNS were excluded. The recipients were divided into three groups: familial/syndromic, presumed primary, and undetermined FSGS/SRNS. Patients who met all of the following criteria were categorized as having presumed primary FSGS/SRNS: (i) nephrotic syndrome, (ii) complete or partial remission with initial steroid therapy and/or additional immunosuppressive therapies, and (iii) diffuse foot process effacement on electron microscopy in the native kidney biopsy. All patients underwent genetic testing using next-generation sequencing. RESULTS: Twenty-four patients from 23 families were analyzed in this study. Pathogenic or likely pathogenic variants in FSGS/SRNS-related genes were identified in four of four families, zero of eight families, and 10 of 11 families with familial/syndromic, presumed primary, and undetermined FSGS/SRNS, respectively. Post-transplant recurrence only occurred in patients with presumed primary FSGS/SRNS. CONCLUSIONS: Our systematic approach based on precise clinicopathological findings including nephrotic syndrome, treatment responses, and diffuse foot process effacement might be useful to differentiate pediatric kidney transplant recipients with FSGS/SRNS who are likely to have a monogenic cause from patients who are not, and to predict post-transplant recurrence. A higher resolution version of the Graphical abstract is available as Supplementary information.

Cancer After Pediatric Kidney Transplantation: A Long-term Single-center Experience in Japan.

BACKGROUND: The cancer incidence, types, and risk factors after pediatric kidney transplantation (KT) have been reported in the United States, Canada, Europe, Australia, and New Zealand. However, no information is available about cancer in pediatric KT recipients in Asian countries. METHODS: Children aged <20 y who underwent initial KT from 1983 to 2016 were analyzed. We compared the cancer incidence with that in the general Japanese population using standardized incidence ratio and examined posttransplant cancer risk using Cox proportional hazards models. RESULTS: A total of 356 children (median age, 11.7 y; interquartile range, 5.0-17.6) received KT with a follow-up period of 4466 person-years. The median age of cancer onset was 18.5 y (interquartile range, 8.0-32.3), and 13 cancers occurred in 12 patients (3.4%). Two patients died from cancer. The most common cancers were posttransplant lymphoproliferative disorders (PTLDs) (38.5%). The median time to PTLD and non-PTLD diagnosis after KT was 0.6 and 16.4 y, respectively. There was no occurrence of skin cancer. The posttransplant cancer incidence was 9.9 times higher than that in the general age-matched population (standardized incidence ratio = 9.9; 95% confidence interval, 4.80-18.39). The cumulative cancer incidence was 5.3% in 20 y after KT, which is lower than that reported in previous studies. We could not identify any risk factors for all cancer after KT in all patients, whereas subgroup analysis in 264 patients with available data of recipient Epstein-Barr virus serological status showed that recipient Epstein-Barr virus-negative serology was an independent risk factor for cancer development. CONCLUSIONS: The incidence of cancer is higher in Japanese pediatric KT recipients than in the general population. The cumulative incidence of cancer after KT was lower in our population than that previously reported. This may be because there was no skin cancer observed in the Japanese pediatric KT recipients in our study.

[Pathological Findings of Chronic Effects Observed in the Kidneys Exposed to Antineoplastic Agents in Two Adolescent Patients].

Cisplatin and ifosfamide are well-known nephrotoxic agents that can cause acute and chronic glomerular and/or tubular toxicity. We examined 2 adolescent patients who were receiving cisplatin and ifosfamide treatments. Pathological findings of patient 1 showed acute tubular necrosis-like patchy injury. Tubulointerstitial nephrosis and glomerular sclerosing were revealed in patient 2. These findings were consistent with the known damages induced by cisplatin and ifosfamide. Proteinuria and mild decline of eGFR were noticed after more than 10 months after the completion of the treatment. It is important to monitor such consequences in long-term follow up. Adult based medical services are required for childhood and adolescent cancer survivors.

Renal hypoplasia can be the cause of membranous nephropathy-like lesions.

BACKGROUND: Renal hypoplasia (RH) is the most common cause of chronic kidney disease in children. In cases of RH, proteinuria is often induced by glomerular hypertrophy and hyperfiltration that is commonly associated with focal segmental glomerulosclerosis. This study reports the first case series of a possible association between RH and membranous nephropathy (MN). METHODS: Of the 168 children with RH who visited our department between 1999 and 2017, five with overt proteinuria (≥ 1 g/gCr) underwent renal biopsy. We retrospectively reviewed the medical charts and analyzed biopsy specimens using light microscopy (LM), immunofluorescence (IF), and electron microscopy. RESULTS: The five children (four boys and one girl) had a median age of 5.5 years at the time of renal biopsy. The median proteinuria was 4.23 g/gCr (range 1.46-14.25), median serum albumin, 2.9 g/dL (range 2.3-3.7), and median estimated glomerular filtration rate, 59.7 mL/min/1.73 m2 (range 36.7-103.6). LM showed segmental spike formation and mesangial hypercellularity and IF study showed segmental granular immunoglobulin G (IgG) staining (IgG1 and IgG3 dominant) along the capillary loops in all five patients. Electron-dense deposits were observed in the subepithelial and mesangial areas. Thus, the pathological studies showed MN-like lesions in all patients. CONCLUSION: Our study suggests that RH can be the cause of MN-like lesions.

Long-term outcome of renal transplantation in childhood-onset anti-neutrophil cytoplasmic antibody-associated vasculitis.

BACKGROUND: There have been a few reports of RTx for AAV in children; however, post-transplant recurrence rate and long-term prognosis remain unclear. Here, we describe the long-term outcomes of RTx in childhood-onset AAV. METHODS: We conducted a retrospective study of children who underwent RTx for AAV between 1999 and 2017 and had a follow-up period of >2 years. RESULTS: Seven patients consisting of three children with MPA and four with RLV were analyzed. Age at Dx was 5.9 (median; range, 4.1-14.5) years. PD was instituted in all patients, and median time on dialysis was 26 (range, 14-63) months. Age at RTx was 12.8 (median; range, 8.7-16.3) years. There were no recurrences of AAV noted during the median follow-up period of 7.0 (range, 2.7-18.8) years after RTx. Graft loss occurred in one patient due to non-adherence. Estimated glomerular filtration rate of the remaining patients at the last follow-up was 73.0 (median; range, 50.7-93.9) mL/min/1.73 m2 . No malignancies and deaths occurred during the observational period. CONCLUSIONS: Our study suggests that RTx for AAV with ESRD is a potentially safe and effective treatment choice for children with AAV.

A grading system that predicts the risk of dialysis induction in IgA nephropathy patients based on the combination of the clinical and histological severity.

Histological classification is essential in the clinical management of immunoglobulin A nephropathy (IgAN). However, there are limitations in predicting the prognosis of IgAN based on histological information alone, which suggests the need for better prognostic models. Therefore, we defined a prognostic model by combining the grade of clinical severity with the histological grading system by the following processes. We included 270 patients and explored the clinical variables associated with progression to end-stage renal disease (ESRD). Then, we created a predictive clinical grading system and defined the risk grades for dialysis induction by a combination of the clinical grade (CG) and the histological grade (HG). A logistic regression analysis revealed that the 24-h urinary protein excretion (UPE) and the estimated glomerular filtration rate (eGFR) were significant independent variables. We selected UPE of 0.5 g/day and eGFR of 60 ml/min/1.73 m2 as the threshold values for the classification of CG. The risk of progression to ESRD of patients with CG II and III was significantly higher than that of patients with CG I. The patients were then re-classified into nine compartments based on the combination of CG and HG. Furthermore, the nine compartments were grouped into four risk groups. The risk of ESRD in the moderate, high, and super-high-risk groups was significantly higher than that in the low-risk group. Herein, we are giving a detailed description of our grading system for IgA nephropathy that predicted the risk of dialysis based on the combination of CG and HG.

Predominant but silent C1q deposits in mesangium on transplanted kidneys - long-term observational study.

BACKGROUND: C1q nephropathy (C1qN) was first described as glomerular disease characterized by predominant meangial C1q deposits in patients with proteinuria and no evidence of systemic lupus erythematosus. Several studies, however, revealed the clinical heterogeneity of C1qN, showing some cases with normal urinalysis. To confirm the existence of cases with predominant mesangial C1q deposits and negative or mild proteinuria and/or hematuria, we investigated renal graft biopsy specimens showing negative to mild proteinuria (less than or equal to 1+ by dip stick test) and/or hematuria. METHODS: Eligible participants were kidney transplant cases who corresponded to the criteria for C1qN and were followed more than 10 years. Their medical records were reviewed to determine the age at detection of predominant mesangial C1q deposits, gender, original renal disease and reason for renal graft biopsy, blood pressure, degree of proteinuria and hematuria, and serum creatinine levels. RESULTS: From 414 cases in adults and children, five pediatric patients (the male to female ratio, 1:1.5) were eligible. At the time when predominant mesangial C1q deposits were detected, 2 cases presented with mild proteinuria without hematuria, but the other 3 cases showed normal urinalysis. Light microscopy revealed minor glomerular abnormality in all the cases. Immunofluorescent study showed predominant mesangial C1q deposits with IgG, IgM and C3 in all cases. All selected specimens presented electron dense-depos in the mesangium. Ten years later from the detection, 2 cases continued to be normal urinalysis and 3 cases had mild proteinuria without hematuria. During this follow-up period, no cases presented with persistent proteinuria and/or hematuria greater than or equal to 2+ by dip stick test. And no cases developed systemic lupus erythematosus. Follow-up renal graft biopsies were performed once in 2 cases 8 years later from the detection. They showed minor glomerular abnormalities. C1q deposit disappeared in one case. In another case, immunofluorescent study was not examined. CONCLUSIONS: This long-term observational study on transplanted kidneys confirms the existence of cases with predominant but silent C1q deposits in the mesangium who have negative or mild proteinuria.

Gonadal tumor in Frasier syndrome: a review and classification.

Frasier syndrome is a rare inherited disease characterized by steroid-resistant nephrotic syndrome, gonadal tumor, and male pseudohermaphroditism (female external genitalia with sex chromosomes XY), which is based on a splice site mutation of Wilms tumor-suppressor gene 1 (WT1). Several unusual Frasier syndrome cases have been reported in which male pseudohermaphroditism was absent. We reviewed 88 Frasier syndrome cases in the literature and classified them into three types (type 1-3) according to external genitalia and sex chromosomes, and described their clinical phenotypes. Type 1 Frasier syndrome is characterized by female external genitalia with 46,XY (n = 72); type 2 by male external genitalia with 46,XY (n = 8); and type 3 by female external genitalia with 46,XX (n = 8). Clinical course differs markedly among the types. Although type 1 is noticed at the mean age of 16 due to mainly primary amenorrhea, type 2 and 3 do not present delayed secondary sex characteristics, making diagnosis difficult. The prevalence of gonadal tumor is high in type 1 (67%) and also found in 3 of the 8 type 2 cases, but not in any type 3 cases, which emphasize that preventive gonadectomy is unnecessary in type 3. On the basis of our findings, we propose a new diagnostic algorithm for Frasier syndrome.

Reference glomerular filtration rate levels in Japanese children: using the creatinine and cystatin C based estimated glomerular filtration rate.

BACKGROUND: The present study was performed to determine the reference values of glomerular filtration rate (GFR) in children by age using the new eGFR equations derived from serum creatinine (Cr) and cystatine C (cysC). METHODS: A total of 1137 children (509 males and 628 females) between the ages of 3 months and 16 years presenting at our facilities between 2008 and 2009 without diseases affecting the renal function were included in this study as in our previous reports for reference values of serum Cr and cysC. We calculated eGFR with the Cr based equation in children aged 2-16 years, and with the cysC based equation in those aged 3-23 months, and determined the reference values of GFR in Japanese children by each age group. RESULTS: We reviewed the median, 2.5 and 97.5 percentile of GFR reference value in each age group. The medians of reference GFRs are 91.7, 98.5, 106.3, and 113.1 mL/min/1.73 m(2) in children aged 3-5, 6-11, 12-17, and 18 months-16 years, respectively. CONCLUSION: We determined the normal reference values of GFR in children. It is important for pediatricians who examine pediatric chronic kidney disease patients to know the values of normal renal function.

Cystatin C-based equation for estimating glomerular filtration rate in Japanese children and adolescents.

BACKGROUND: Renal inulin clearance is the gold standard for evaluation of kidney function, but is compromised by problems of collecting urine samples in children, especially those <6 years or with a bladder dysfunction. Therefore, we should utilize the serum cystatin C (cysC)-based estimated glomerular filtration rate (eGFR) for measuring serum cysC. The purpose of the present study is to determine the applicability of the new serum cysC-based eGFR in Japanese children and adolescents, including infants with chronic kidney disease (CKD), for evaluation of renal function. METHODS: Inulin clearance and standardized serum cysC level determined by the colloidal gold immunoassay were measured in 135 pediatric CKD patients between the ages of 1 month and 18 years with no underlying disease that affects renal function except CKD, to determine serum cysC-based eGFR in Japanese children and adolescents. RESULTS: We showed the inulin clearance by expression of 1/serum cysC in pediatric CKD patients, which resulted in the equation: inulin GFR (mL/min/1.73 m(2)) = 104.1 × 1/serum cysC (mg/L) - 7.80. We also validated the cysC-based eGFR formula for Japanese adults. eGFR values obtained with the adult formula significantly underestimated GFR by approximately 8 % in children with CKD. CONCLUSION: We determined the new cysC-based eGFR formula is useful for clinical screening of renal function in Japanese children and adolescents, including infants.

Overestimation of the risk of progression to end-stage renal disease in the poor prognosis' group according to the 2002 Japanese histological classification for immunoglobulin A nephropathy.

BACKGROUND: The current (2012) histological classification of immunoglobulin A nephropathy was established using a case-control study of 287 patients. However, the risk of progression to end-stage renal disease (ESRD) has not been validated for the previous (2002) classification. This study aimed to determine whether the previous classification could identify the risk of long-term renal outcome through re-analysis of the 2012 cohort. METHODS: On the basis of the 2002 classification, namely 'good prognosis', 'relatively good prognosis', 'relatively poor prognosis', and 'poor prognosis', we examined the clinical data at the time of biopsy, the correlation between the 2002 classification and long-term renal outcomes, and a patient-by-patient correlation between the 2002 and 2012 classification systems. This was performed by analyzing samples from the 287 patients used to establish the 2012 classification. RESULTS: The rate of decline of estimated glomerular filtration rate was greater and the odds ratio of progression to ESRD was higher in the 'poor prognosis' group. In contrast, the odds ratio for renal death was comparable between the groups described as 'relatively poor prognosis' and 'relatively good prognosis' in the 2002 classification. Many patients in the 2002 classification were classified with a lower histological grade in the current classification, but none were classified with a higher grade. CONCLUSIONS: The 2002 classification could also identify the risk of progression to ESRD. However, it was overestimated for patients in the 'poor prognosis' group in the 2002 classification, as that group included patients with milder histological damage.

Successful living-related kidney transplantation in a boy with inherited dysfibrinogenemia.

In kidney transplantation, it is essential to avoid acute vascular complications, such as hemorrhage and renal vascular thrombosis, which may often lead to allograft loss. Inherited dysfibrinogenemia is a rare coagulation disorder with a wide spectrum of clinical manifestations, such as excessive bleeding and thrombosis. A 12-yr-old boy, previously diagnosed with renal hypodysplasia, was found to have reduced fibrinogen concentrations. Coagulation tests assessing surgical risk during kidney transplantation showed a discrepancy between functional and immunologic fibrinogen concentrations. Gene analysis confirmed inherited dysfibrinogenemia, with a heterozygous mutation in FGA (Aα Arg16His) in the patient and his mother. Based on the molecular and functional properties of the mutation, and a familial phenotype, in which his aunt had experienced a previous bleeding episode, the patient was considered at greater risk of bleeding than of thrombosis. The patient was administered fibrinogen concentrate before surgery, and kidney transplantation was performed with his father as the organ donor. The patient received additional prophylactic infusions of fibrinogen concentrate postoperatively, and his postoperative course was uneventful. Accurate diagnosis of dysfibrinogenemia, including gene analysis, is important for correctly managing patients with this coagulation disorder who are undergoing kidney transplantation.

Immunohistological study of a pediatric patient with plasma cell-rich acute rejection.

We report here the case of a girl who developed plasma cell-rich acute rejection (PCAR), a condition characterized by the presence of mature plasma cells infiltrating a renal allograft. The patient's creatinine level increased sharply to 4.3 mg/dL from 0.9 mg/dL at 19 months post-renal transplantation. She showed no response to methylprednisolone pulse therapy at a dose of 500 mg for three d but did show an immediate clinical and histopathological response to muromonab-CD3 (OKT3) administration. She had two episodes of PCAR recurrence and subsequently lost her graft. She had no evidences of antibody-mediated rejection including C4d deposition in peritubular capillaries and donor-specific antibodies during the entire follow-up period. To elucidate the pathogenesis of PCAR, immunohistological examination of infiltrating cells was performed. CD3-positive cells infiltration seemed to be associated with the CD138-positive cells infiltration, and the number of CD3-positive cells was increased preceding PCAR recurrence. Additionally, a rapid decrease in the number of CD138-positive cells and CD3-positive cells following the OKT3 administration was observed. This case suggests that T-cell mediated immune mechanisms might play a role in the development of PCAR.

Pretransplantation combined therapy with plasmapheresis and rituximab in a second living-related kidney transplant pediatric recipient with a very high risk for focal segmental glomerulosclerosis recurrence.

Prophylactic PP can provide some protection against post-transplantation recurrences of FSGS, but it cannot prevent recurrences in all cases. Therefore, new preventive therapies are needed. We report on a 7.9-yr-old girl treated with pretransplantation prophylactic combined therapy consisting of four sessions of PP and one dose of rituximab before a second living-related KTX. The patient had a very high risk of post-transplantation FSGS recurrence because this had occurred after the first KTX. During the 36 months since the second transplantation, she has had no evidence of proteinuria or significant infectious complications. Although our experience is too preliminary to draw any generalizable conclusions, pretransplantation combined therapy with PP and rituximab might be a possible option for the prevention of FSGS recurrence in very high-risk recipients undergoing living-donor KTXs.

Asymptomatic high Epstein-Barr viral load carriage in pediatric renal transplant recipients.

High viral load carriage of EBV is one of the risks for PTLD in transplant recipients. We reviewed retrospectively in pediatric renal transplant recipients with EBV seronegative. EBV loads in peripheral blood and EBV-CTLs were measured every 1-3 months in 13 patients after grafting. Immunosuppressants were reduced when the patients were considered to have persistent high EBV loads (>1000 copies/µgDNA for over six months). All showed primary EBV infection: six with asymptomatic persistent high EBV loads (group A) and seven with neither EBV-associated symptoms nor persistent high EBV loads (group B). No patient developed PTLD in either group. Chronic rejection occurred in one patient in group A after immunosuppressants' reduction. There was no difference in renal dysfunction rates between the two groups. The maximum and increase rates in EBV loads were significantly higher in group A. The CTLs' percentage was significantly lower in group A when EBV loads first rose above 100 copies/µg DNA. This study suggests the possibility that EBV loads and CTLs' monitoring may be useful for avoidance of PTLD, as patients with asymptomatic persistent high EBV loads had higher EBV loads and lower percentages of CTLs.

Medullary ray injury in renal allografts.

Non-immune injury leading to interstitial fibrosis and tubular atrophy (IF/TA) in renal allografts has various etiologies, but pathological means of verification have yet to be developed. Medullary ray injury (MRI) is a pathological feature of many non-immune injuries inducing IF/TA and pathological determination of calcineurin inhibitor (CNI) toxicity proceeding to striped fibrosis. We investigated the contribution of CNI toxicity to MRI and other non-immune etiologies related to IF/TA. In this study MRI is defined as fibrosis and inflammation localized exclusively to the medullary ray. Thirty-six protocol biopsies showing MRI were analyzed and classified histopathologically as following: MRI related to CNI toxicity; chronic obstruction or reflux nephropathy; and acute or chronic pyelonephritis. The etiology of MRI was CNI toxicity (n= 16, 44.4%), chronic obstruction (n= 13, 36.1%), acute or chronic pyelonephritis (n= 2, 5.6%), and other (n= 5, 13.9%). We performed cystography in seven cases of MRI related to chronic obstruction or reflux nephropathy and six cases showing vesicoureteral reflux. The ci+ct score showed significant progression after one year in 30 of the 36 cases (1.53 ± 1.04 vs. 3.03 ± 1.13, P < 0.01). MRI has various etiologies and may also predict changes in urological complications. The classification of MRI may be useful to determine the non-immune etiology leading to IF/TA.

Beneficial effect of chlorambucil in steroid-dependent and cyclophosphamide-resistant minimal change nephrotic syndrome.

BACKGROUND: Little information is available on the effect of second cytotoxic therapy in steroid-dependent children with minimal change nephrotic syndrome (MCNS). METHODS: Response to second cytotoxic therapy and side effects were reviewed in 33 steroid-dependent and cyclophosphamide-resistant children with MCNS who received chlorambucil (n=11, group 1) or cyclophosphamide (n=22, group 2). RESULTS: Age at onset of nephrosis, beginning of first and second therapy, sex ratio, duration of nephrosis before first cytotoxic therapy, interval between first and second cytotoxic therapy, number of relapses, cumulative doses of steroids and length of remission off steroids before second therapy were similar between groups. Four patients (36.4%, p<0.05) in group 1 remained in remission for a median 34.0 months, whereas only 1 patient (4.5%) in group 2 did for 53.0 months. Two patients in group 1 and 1 patient in group 2 became infrequent relapsers. Total number of nonrelapsers and infrequent relapsers was higher in group 1 (54.5%, p<0.05) than in group 2 (9.1%). Number of relapses and cumulative doses of steroids were reduced and length of remission off steroids was longer in group 1 than in group 2 (p<0.05). There was no difference between groups in frequency of side effects, and none had serious toxicity. However, the short period of follow-up in our study does not exclude the risk of azoospermia. CONCLUSIONS: Our data suggest a superior effect of chlorambucil over cyclophosphamide in steroid-dependent and cyclophosphamide-resistant children with MCNS. A future randomized controlled clinical trial is required to confirm our findings.

Screening of vesicoureteral reflux in pediatric patients with kidney transplantation showing non-specific interstitial fibrosis and tubular atrophy with interstitial Tamm-Horsfall protein deposits in protocol allograft biopsy.

Interstitial fibrosis and tubular atrophy (IF/TA) in kidney allografts are induced by multiple factors, and although much effort has been devoted on the classification of IF/TA, clarification of the causes of non-specific IF/TA is equally important for appropriate therapy. Tamm-Horsfall protein (THP) in renal tissue can be a useful marker for the histological expression of urine backflow and suspected vesicoureteral reflux (VUR). Here, we examined the presence of VUR in pediatric recipients with interstitial THP deposits in kidney allografts to clarify the cause of non-specific IF/TA. Ten pediatric patients showing interstitial THP deposits with non-specific IF/TA were enrolled and voiding cystourethrography was performed. Major histological findings of these patients were interstitial mononuclear cell infiltration and fibrosis associated with interstitial THP deposits. The semiquantitative grading scores of IF/TA were as follows: (i) mild IF/TA (n = 3); (ii) moderate IF/TA (n = 3); and (iii) severe IF/TA (n = 4). In the severe grade, diffuse interstitial mononuclear cell infiltrates were prominent with the appearance of thyroidization classically observed in chronic pyelonephritis. Eight of ten patients (80%) had VUR into the graft. Although symptomatic pyelonephritis was not observed in any of the patients, asymptomatic bacteriuria was detected in 40.0% of the patients. There was no significant correlation between VUR grade and IF/TA histological score. The patients without VUR also showed mild or severe IF/TA. Therefore, VUR and urinary flow stasis accompanied by asymptomatic urinary tract infection appear to be the causes of interstitial mononuclear cell infiltration and fibrosis associated with interstitial THP deposits in kidney allografts.

Clinical features and mutational survey of NPHS2 (podocin) in Japanese children with focal segmental glomerulosclerosis who underwent renal transplantation.

Recurrent FSGS is a major challenge in the field of nephrology. To clarify the role of NPHS2 defects in the pathogenesis of FSGS recurrence, we sequenced all eight exons of NPHS2 in 11 Japanese pediatric FSGS patients with or without post-transplant recurrence. All patients had biopsy-proven primary FSGS, had no family history of renal diseases or consanguinity, were steroid-resistant, and received living-related renal transplantation. The mean age at onset was 5.0 +/- 3.1 yr and mean age at renal transplantation was 10.4 +/- 4.1 yr. Mutational analysis of NPHS2 was performed using polymerase chain reaction and direct sequencing. We found a synonymous T/C polymorphism at alanine 318 (GCC to GCT) in seven of 11 patients but no other causative NPHS2 mutations. FSGS recurred immediately after transplant in seven patients, while the remaining four patients had no recurrence for 3.2-5.8 yr. There were no differences between recurrent and non-recurrent patients in the onset age and the interval from onset to ESRD. In conclusion, we detected no causative NPHS2 mutations in Japanese pediatric FSGS patients with or without post-transplant recurrence. Further studies on the involvement of other genes are required to better understand recurrent FSGS.

Monitoring of Epstein-Barr virus load and antibody in pediatric renal transplant patients.

BACKGROUND: Epstein-Barr virus (EBV) infection can lead to life-threatening post-transplant lymphoproliferative disorder (PTLD). The aim of the present study was to establish EBV monitoring methods to prevent PTLD. METHODS: EBV-DNA load was investigated, using real-time polymerase chain reaction (PCR) and anti-EBV antibody titers, in peripheral blood mononuclear cells of 21 renal transplant patients (seven recipients who were EBV-seronegative, R[-]; 14 who were EBV-seropositive, R[+]) before grafting. The mean age at entry and the mean follow-up period was 7.8 years of age (range, 3.3-12.0 years) and 1.8 years (range, 0.4-4.0 years), respectively, in the R(-) group, and 12.5 years of age (range, 3.9-17.7 years) and 3.8 years (range, 0.8-8.2 years) in the R(+) group, respectively. RESULTS: The mean maximum load of the EBV genome was 1071 copies/microg DNA (range, 106-20700 copies/microg DNA) in the R(-) group, and 61 copies/microg DNA (range, <50-552 copies/microg DNA) in the R(+) group. During follow up no patient in the R(+) group had any noticeable symptoms that could be related to EBV, but three recipients in the R(-) group developed EBV-related symptoms including adenoid hypertrophy, cervical lymphadenopathy, and PTLD (B cell lymphoma), in one patient each. In the R(-) group the first leukocyte-associated viremia was detected at 30-180 days, and seroconversion at 43-266 days after transplantation. CONCLUSIONS: Viral DNA detection using PCR is a useful tool for EBV surveillance, but the maximum EBV load was not markedly elevated (2474 copies/microg DNA) in a patient with PTLD. Therefore, EBV surveillance using only monitoring of EBV load in peripheral leukocyte may be insufficient. Histology may therefore be necessary to accurately diagnose PTLD.