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.

Amount and selectivity of proteinuria may predict the treatment response in post-transplant recurrence of focal segmental glomerulosclerosis: a single-center retrospective study.

BACKGROUND: Primary focal segmental glomerulosclerosis (FSGS) frequently recurs after kidney transplantation and is associated with poor graft survival. To date, few studies have investigated predictive factors for treatment responses in recurrent FSGS. METHODS: We retrospectively analyzed 16 patients who were < 16 years at the age of onset and had post-transplant recurrence of FSGS from 1993 to 2018. Patients who achieved complete remission or partial remission after initiating therapy for recurrent FSGS were defined as responders. We compared several clinical characteristics between responders and non-responders. Time to remission was also analyzed. RESULTS: Ten patients were responders, and six patients were non-responders. Univariate analysis showed that responders had a significantly lower amount of maximum proteinuria at the time of recurrence (P = 0.015) and more highly selective proteinuria (P = 0.013) than non-responders. The time to remission from initiation of therapy was 2 months (interquartile range 0.2-4.4). In all responders, except for one patient, remission was achieved within 6 months. CONCLUSIONS: Therapeutic responses may be predicted by examining the amount and selectivity of proteinuria at the time of recurrence. Further studies with larger numbers of patients are clearly required to validate these findings.

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.

Individualized concept for the treatment of autosomal recessive polycystic kidney disease with end-stage renal disease.

Management of children with autosomal recessive polycystic kidney disease (ARPKD) who develop end-stage renal disease (ESRD) remains challenging because of concomitant liver disease. Patients with recurrent cholangitis are candidates for liver-kidney transplantation, while the treatment for patients with splenomegaly and pancytopenia due to portal hypertension is controversial. Herein, we report 7 children who were treated using an individualized treatment strategy stratified by liver disease. Two patients with recurrent cholangitis underwent sequential liver-kidney transplantation, while 4 patients with splenomegaly and pancytopenia but without recurrent cholangitis underwent splenectomy followed by isolated kidney transplantation. The remaining patient, who did not have cholangitis and pancytopenia, underwent isolated kidney transplantation. Blood cell counts were normalized after splenectomy was performed at the median age of 8.7 (range, 7.4-11.7) years. Kidney transplantation was performed at the median age of 8.8 (range, 1.9-14.7) years in all patients. Overwhelming post-splenectomy infections and cholangitis did not occur during the median follow-up period of 6.3 (range, 1.0-13.2) years. The estimated glomerular filtration rate at the last follow-up was 53 (range, 35-107) mL/min/1.73 m2 . No graft loss occurred. Our individualized treatment strategy stratified by recurrent cholangitis and pancytopenia can be a feasible strategy for children with ARPKD who develop ESRD and warrants further evaluation.

New-onset diabetes after renal transplantation in a patient with a novel HNF1B mutation.

CAKUT are the most frequent causes of ESRD in children. Mutations in the gene encoding HNF1B, a transcription factor involved in organ development and maintenance, cause a multisystem disorder that includes CAKUT, diabetes, and liver dysfunction. Here, we describe the case of a patient with renal hypodysplasia who developed NODAT presenting with liver dysfunction. The NODAT was initially thought to be steroid and FK related. However, based on the patient's clinical features, including renal hypodysplasia and recurrent elevations of transaminase, screening for an HNF1B mutation was performed. Direct sequencing identified a novel splicing mutation of HNF1B, designated c.344 + 2T>C. Because CAKUT is the leading cause of ESRD in children and HNF1B mutations can cause both renal hypodysplasia and diabetes, HNF1B mutations may account for a portion of the cases of NODAT in pediatric patients who have undergone kidney transplantation. NODAT is a serious and major complication of solid organ transplantation and is associated with reduced graft survival. Therefore, for the appropriate management of kidney transplantation, screening for HNF1B mutations should be considered in pediatric patients with transplants caused by CAKUT who develop NODAT and show extra-renal symptoms.

Decreased glomerular filtration as the primary factor of elevated circulating suPAR levels in focal segmental glomerulosclerosis.

BACKGROUND: Circulating factor(s) has been thought to be the underlying cause of focal segmental glomerulosclerosis (FSGS), and recent studies foster this idea by demonstrating increased soluble urokinase receptor (suPAR) levels in the serum of FSGS patients. METHODS: To explore the possible contribution of suPAR in FSGS pathogenesis, we analyzed serum suPAR levels in 17 patients with FSGS and compared them with those in patients with steroid-sensitive nephrotic syndrome, chronic glomerulonephritis, or non-glomerular kidney diseases. RESULTS: Serum suPAR levels in patients with FSGS were higher than those in patients with steroid-sensitive nephrotic syndrome or chronic glomerulonephritis, but not higher than those in patients with non-glomerular kidney diseases. suPAR levels negatively correlate with estimated glomerular filtration rate and were decreased after renal transplantation in patients with FSGS as well as in those with non-glomerular kidney diseases. Furthermore, 6 FSGS patients with post-transplant recurrence demonstrated that suPAR levels were not high during the recurrence. CONCLUSIONS: Based on our results, elevated suPAR levels in FSGS patients were attributed mainly to decreased glomerular filtration. These data warrant further analysis for involvement of possible circulating factor(s) in FSGS pathogenesis.

Final adult height in kidney recipients who underwent highly successful transplantation as children: a single-center experience.

BACKGROUND: Achieving a normal final adult height (FH) remains a challenge in the field of pediatric kidney transplantation (KTx). To examine the optimal approach to assuring normal FH following KTx, we retrospectively examined the post-transplant growth and FH of pediatric KTx recipients. METHODS: Since the relevant factors affecting the FH of children following KTx are multifactorial and notably complex, KTx recipients with persistent good graft function and successful steroid minimization until FH attainment were selected for this study. RESULTS: Thirteen patients were enrolled in this study. The mean estimated glomerular filtration rate was 72.1 ± 15.3 ml/min/1.73 m(2), and the mean corticosteroid dose was 0.05 ± 0.05 mg/kg on alternate days at the time of FH attainment. Despite highly successful KTx, four (30.8 %) patients (one who underwent KTx before puberty and three during puberty) showed a decrease in the height standard deviation score (hSDS) from the time of KTx until FH attainment. Moreover, of these, two male patients had an FH with an SD <-2. CONCLUSION: FH remained suboptimal despite highly successful KTx. Not only highly successful KTx but also further treatment such as steroid avoidance, early steroid withdrawal or using rhGH might be necessary to assure a normal FH in some pubertal patients.

Plasma homocysteine and folate levels and dietary folate intake in adolescents and young adults who underwent kidney transplantation during childhood.

BACKGROUND: Hyperhomocysteinemia (hyper-Hcy) is an important and reversible cardiovascular disease risk factor. We examined the prevalence of hyper-Hcy, plasma folate levels, and dietary folate intake in adolescents and young adults who had undergone kidney transplantation during childhood to assess the necessity for managing dietary folate. METHODS: This cross-sectional study was performed in 89 kidney transplant recipients (age at kidney transplantation: 12.6 ± 4.1 years; age during study: 21.2 ± 5.5 years). Hyper-Hcy and plasma folate deficiency were defined as plasma homocysteine (Hcy) >15 nmol/ml and plasma folate <3.0 ng/ml, respectively. RESULTS: Of the patients, 60 (67.4 %) had hyper-Hcy and 14 (15.7 %) had plasma folate deficiency. Plasma homocysteine levels correlated negatively with estimated glomerular filtration rate (eGFR; r = -0.565, p < 0.01) and plasma folate levels (r = -0.434, p < 0.01). For determinants of plasma homocysteine levels, a priori selected variables included kind of calcineurin inhibitor, age at kidney transplantation, pretransplant duration of dialysis, time since transplantation, age at examination, eGFR, and plasma folate. Stepwise multiple linear regression analysis revealed eGFR and plasma folate levels as significant independent variables influencing plasma homocysteine levels. Dietary folate intake in 11 of 16 patients (66.8 %) with eGFR ≥ 60 ml/min/1.73 m(2) was below the recommended dietary allowance for Japanese. CONCLUSIONS: The prevalence of hyper-Hcy and plasma folate deficiency, as well as the low dietary folate intake, suggest that dietary management of folate is necessary for adolescents and young adults who have undergone kidney transplantation during childhood.

Podocyte expression of nonmuscle myosin heavy chain-IIA decreases in idiopathic nephrotic syndrome, especially in focal segmental glomerulosclerosis.

BACKGROUND: Previous studies have identified significant associations between the development of idiopathic focal segmental glomerulosclerosis (FSGS) and MYH9 encoding nonmuscle myosin heavy chain-IIA (NMMHC-IIA). However, these studies focused only on the linkage of MYH9 polymorphisms and development of FSGS. There have been no reports on pathological changes of NMMHC-IIA in human glomerular diseases. Here we report on the precise localization of NMMHC-IIA in podocytes and changes in NMMHC-IIA expression in pathological states in rats and humans. METHODS: Immunocytochemical (immunofluorescence and immunoelectron microscopy) studies were performed to determine the precise localization of NMMHC-IIA. Expression levels of NMMHC-IIA were investigated in puromycin aminonucleoside (PAN)-treated rats; and expression levels of NMMHC-IIA and other podocyte-related proteins were investigated in glomeruli of patients with idiopathic FSGS and other heavy proteinuric glomerular diseases. RESULTS: NMMHC-IIA was located primarily at the cell body and primary processes of podocytes; this localization is distinct from other podocyte-related molecules causing hereditary FSGS. In PAN-treated rat kidneys, expression levels of NMMHC-IIA in podocytes decreased. Immunohistochemical analysis revealed that expression levels of NMMHC-IIA markedly decreased in idiopathic nephrotic syndrome, especially FSGS, whereas it did not change in other chronic glomerulonephritis showing apparent proteinuria. Changes in NMMHC-IIA expression were observed in glomeruli where expression of nephrin and synaptopodin was maintained. CONCLUSIONS: Considering previous genome-wide association studies and development of FSGS in patients with MYH9 mutations, the characteristic localization of NMMHC-IIA and the specific decrease in NMMHC-IIA expression in idiopathic nephrotic syndrome, especially FSGS, suggest the important role of NMMHC-IIA in the development of FSGS.

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.

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.

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.