Nephronophthisis 13 caused by WDR19 variants with pancytopenia: case report.

We present a case of nephronophthisis 13 that resulted from WDR19 variants. The patient, a nine-year-old Japanese boy, had detection of mild proteinuria during a school urine screening. Urinalysis revealed mild proteinuria without hematuria. Blood tests indicated pancytopenia, mild elevation of liver enzymes, and kidney dysfunction. Ultrasound examination disclosed hepatosplenomegaly. Abdominal computed tomography and bone marrow assessments ruled out malignant tumors. Subsequent kidney and liver biopsies suggested nephronophthisis and congenital hepatic fibrosis. Furthermore, comprehensive genetic analysis through next-generation sequencing revealed compound heterozygous variants in WDR19 (NM_025132.4), including the previously reported c.3533G > A, p.(Arg1178Gln), and c.3703G > A, p.(Glu1235Lys) variants, confirming the diagnosis of nephronophthisis 13. There is potential need for liver and kidney transplantation in patients with nephronophthisis and hepatic fibrosis. Early diagnosis is therefore crucial to mitigate delays in treating complications associated with kidney and hepatic insufficiency and to facilitate preparation of transplantation. To achieve early diagnosis of nephronophthisis, it is imperative to consider it as a differential diagnosis when extrarenal symptoms and kidney dysfunction coexist, particularly when mild proteinuria is observed through opportunistic urinalysis. Genetic testing is important because nephronophthisis manifests as diverse symptoms, necessitating an accurate diagnosis. Next-generation sequencing was shown to be invaluable for the genetic diagnosis of nephronophthisis, given the numerous identified causative genes.

Clinical characteristics and outcomes of immune-complex membranoproliferative glomerulonephritis and C3 glomerulopathy in Japanese children.

BACKGROUND: Membranoproliferative glomerulonephritis (MPGN) can be divided into immune-complex MPGN (IC-MPGN) and C3 glomerulopathy (C3G), which includes dense deposit disease (DDD) and C3 glomerulonephritis (C3GN). These conditions result from abnormalities in different complement pathways and may lead to different prognoses. However, there are limited studies describing the respective clinical courses. METHODS: In this study, Japanese pediatric patients diagnosed with MPGN based on kidney biopsies conducted between February 2002 and December 2022 were reclassified as having IC-MPGN or C3G (DDD or C3GN). We retrospectively analyzed the clinical characteristics and outcomes of these patients. RESULTS: Out of 25 patients with MPGN, three (12.0%) were diagnosed with DDD, 20 (80.0%) with C3GN, and two (8.0%) with IC-MPGN. There were 13 (65.0%) patients and one (33.3%) patient in remission after treatment for C3GN and DDD, respectively, and no patients with IC-MPGN achieved remission. The median follow-up period was 5.3 (2.5-8.9) years, and none of the patients in either group progressed to an estimated glomerular filtration rate < 15 ml/min/1.73 m2. Patients with C3GN presenting mild to moderate proteinuria (n = 8) received a renin-angiotensin system inhibitor (RAS-I) alone, and these patients exhibited a significant decrease in the urinary protein creatinine ratio and a notable increase in serum C3 levels at the last follow-up. CONCLUSIONS: Most patients with MPGN were diagnosed with C3GN. The remission rate for C3GN was high, and no patients developed kidney failure during the approximately 5-year follow-up. Additionally, patients with C3GN with mild to moderate proteinuria had good outcomes with RAS-I alone, but continued vigilance is necessary to determine long-term prognosis.

Immunohistological analysis reveals IgG1-dominant immunophenotype of tubulointerstitial nephritis unassociated with IgG4-related diseases.

PURPOSE: Tubulointerstitial nephritis (TIN) has various etiologies, including IgG4-related disease (IgG4-RD), autoimmune diseases, antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV), and others. IgG4-positive plasma cell infiltration can occasionally be found in TIN unrelated to IgG4-RD. Therefore, there may be problems with usage of IgG4 immunostaining to differentiate between TIN with and TIN without IgG4-RD. This study aimed to compare the proportion of plasma cells that are positive for each IgG subclass and to clarify the predominant IgG subclass trends and clinical characteristics associated with IgG4-RD and non-IgG4-related interstitial nephritis. METHODS: The study enrolled 44 cases of TIN: 6 of IgG4-RD, 8 of autoimmune disease, 9 of AAV, and 21 of unknown disease group. In addition to clinical characteristics, IgG subclass composition of interstitial plasma cells was evaluated among 4 groups by immunohistochemistry. RESULTS: IgG1 was the predominant IgG subclass in TIN unrelated to IgG4-RD. In the IgG4-RD group, the IgG subclass rate was high in both IgG1 and IgG4. The rate of average IgG4-positive cells was significantly lower in the autoimmune disease group and unknown disease group compared with the IgG4-RD group. CONCLUSION: The present study revealed IgG1-dominant immune profiles of TIN unrelated to IgG4-RD. Further investigation is required to elucidate the clinicopathological differences between IgG1-dominant and IgG4-dominant groups in IgG4-RD.

Histologic and Clinical Factors Associated with Kidney Outcomes in IgA Vasculitis Nephritis.

BACKGROUND: Nephritis is a common manifestation of IgA vasculitis and is morphologically indistinguishable from IgA nephropathy. While MEST-C scores are predictive of kidney outcomes in IgA nephropathy, their value in IgA vasculitis nephritis has not been investigated in large multiethnic cohorts. METHODS: Biopsies from 262 children and 99 adults with IgA vasculitis nephritis ( N =361) from 23 centers in North America, Europe, and Asia were independently scored by three pathologists. MEST-C scores were assessed for correlation with eGFR/proteinuria at biopsy. Because most patients ( N =309, 86%) received immunosuppression, risk factors for outcomes were evaluated in this group using latent class mixed models to identify classes of eGFR trajectories over a median follow-up of 2.7 years (interquartile range, 1.2-5.1). Clinical and histologic parameters associated with each class were determined using logistic regression. RESULTS: M, E, T, and C scores were correlated with either eGFR or proteinuria at biopsy. Two classes were identified by latent class mixed model, one with initial improvement in eGFR followed by a late decline (class 1, N =91) and another with stable eGFR (class 2, N =218). Class 1 was associated with a higher risk of an established kidney outcome (time to ≥30% decline in eGFR or kidney failure; hazard ratio, 5.84; 95% confidence interval, 2.37 to 14.4). Among MEST-C scores, only E1 was associated with class 1 by multivariable analysis. Other factors associated with class 1 were age 18 years and younger, male sex, lower eGFR at biopsy, and extrarenal noncutaneous disease. Fibrous crescents without active changes were associated with class 2. CONCLUSIONS: Kidney outcome in patients with biopsied IgA vasculitis nephritis treated with immunosuppression was determined by clinical risk factors and endocapillary hypercellularity (E1) and fibrous crescents, which are features that are not part of the International Study of Diseases of Children classification.

IgA nephropathy in a boy with frequently relapsing nephrotic syndrome.

A Japanese boy developed nephrotic syndrome (NS) and had microscopic hematuria at 8 years old. Renal biopsy was performed. Light microscopy study revealed mesangial proliferation and all immunofluorescent stains (including IgA) were negative, so he was diagnosed with non-IgA diffuse mesangial proliferation (DMP). Complete remission was achieved at 13 days after the initiation of oral prednisolone, and hematuria also disappeared 3 days later, but the patient developed frequently relapsing nephrotic syndrome. Cyclosporine A (CyA) was introduced at 10 years old, and there were no relapses between then and when it was discontinued at 12 years old. A second renal biopsy revealed minimal change without CyA nephrotoxicity. However, there was repeated relapse of NS after discontinuation, so CyA was reintroduced 8 months later, and NS remained in remission thereafter. Microscopic hematuria appeared at 13 years old, however, with gross hematuria appearing at the time of infection. A third renal biopsy revealed mesangial proliferation with IgA-dominant deposition, so the patient was diagnosed with IgA nephropathy. Currently (14 years old), CyA treatment has been discontinued and the patient is undergoing lisinopril therapy for IgA nephropathy, but there are still relapses of NS. To the best of our knowledge, there have been no previous reports of a patient with non-IgA DMP at the onset of NS who had later development of IgA nephropathy. The patient showed non-IgA DMP at the onset, suggesting that NS with non-IgA DMP and IgA nephropathy has some common pathophysiology. Treatment for NS, such as PSL and/or CyA treatment, may suppress the clinical manifestation of late IgA nephropathy.

Factors related to recurrence of proteinuria in childhood IgA nephropathy.

BACKGROUND: Proteinuria remission is the most significant predictive factor for kidney outcome in childhood IgA nephropathy (c-IgAN). Even if proteinuria remission can be obtained, some patients have recurrence of proteinuria in the long-term. METHODS: This is a retrospective analysis of 312 cases of proteinuria remission among 538 consecutive children with biopsy-proven IgAN from 1976 to 2013. To elucidate the incidence and factors related to recurrence of proteinuria in c-IgAN, we compare clinical and pathological findings between patients with and without recurrence of proteinuria. RESULTS: Among 312 patients with remission of proteinuria, 91 (29.2%) had recurrence of proteinuria within the observation period (median 8 years). Using a multivariate Cox regression analysis, significant factors associated with recurrence of proteinuria were onset age (HR 1.13 [95%CI: 1.05-1.22], P = 0.002) and presence of hematuria after proteinuria remission (HR 2.11 [95%CI: 1.30-3.45], P = 0.003). The Kaplan-Meier analysis showed significant differences in CKD G3a-G5-free survival between the patients with no-recurrence of proteinuria, recurrence of proteinuria and non-proteinuria remission (P < 0.0001, log-rank test). Kidney survival was 100% in no-recurrence of proteinuria, 92.2% in recurrence of proteinuria, and 65.6% in non-proteinuria remission at 15 years. Cox analyses adjusted by proteinuria remission showed that recurrence of proteinuria (HR 03.10e9 [95%CI: NA], P = 0.003) was a significant factor associated with progression to CKD G3a-G5 in all patients with c-IgAN. CONCLUSIONS: Approximately 30% of patients with proteinuria remission had recurrence of proteinuria regardless of treatment. Both remission and recurrence of proteinuria are significant prognostic factors for kidney outcome. A higher resolution version of the Graphical abstract is available as Supplementary information.

Long-term outcome of combination therapy with corticosteroids, mizoribine and RAS inhibitors as initial therapy for severe childhood IgA vasculitis with nephritis.

BACKGROUND: Patients with severe IgA vasculitis with nephritis (IgAVN) typically receive aggressive therapy as an initial approach. We have consistently performed combination therapy including corticosteroids and immunosuppressants as initial therapy for severe IgAVN over a 20-year-plus period, with only minor changes to the treatment protocol. This study seeks to reveal the efficacy of combination therapy for severe IgAVN. METHODS: We retrospectively studied 50 Japanese children diagnosed between 1996 and 2019 with clinicopathologically severe IgAVN who were defined as ISKDC classification grade IIIb-V and/or serum albumin < 2.5 g/dL. RESULTS: The median age at the onset of IgAVN was 8.0 years (IQR: 6.0-10.0). At biopsy, 44% of patients had nephrotic syndrome and 14% had kidney dysfunction. All patients were treated with combination therapy after biopsy. Abnormal proteinuria resolved after initial therapy in all 50 patients. However, eight patients (16%) had recurrence of proteinuria. Abnormal proteinuria was again resolved in three of these patients with additional treatment. At the last follow-up (median 59.5 months; IQR, 26.2-84.2), the median urine protein-to-creatine ratio was 0.08 g/gCr (IQR, 0.05-0.15), and only one patient had kidney dysfunction. CONCLUSIONS: Combination therapy provided good kidney outcomes for Japanese children with severe IgAVN. Even including recurrent cases, the degree of proteinuria was slight, and kidney function was good at the last follow-up. A higher resolution version of the Graphical abstract is available as Supplementary information.

Clinical and pathological investigation of oligomeganephronia.

BACKGROUND: Oligomeganephronia (OMN) is a rare congenital anomaly involving the kidney and urinary tract, characterized by decreased number and compensatory hypertrophy of the nephron. It is caused by abnormal kidney development during the embryonic period, especially in patients with low birth weight; however, the actual etiology and clinical features remain unknown. We aim to reveal the clinical and pathological characteristics, treatment, and outcome. METHODS: Ten patients diagnosed with OMN between 2013 and 2020 were retrospectively investigated. The data were presented as the median ± interquartile range, and statistical significance was set at p < 0.05. RESULTS: The age at diagnosis was 14.1 years, the male-to-female ratio was 6:4, and only four cases were born with low birth weight. The estimated glomerular filtration rate (eGFR) was 62.2 mL/min/1.73 m2. The glomerulus diameter of OMN patients was significantly larger (217 vs. 154 µm, p < 0.001) in OMN patients, and the number of glomeruli of OMN patients was lower (0.89 vs. 2.05/mm2, p < 0.001) than the control group. Eight of the ten cases were identified by urinary screening. Nine patients were treated with renin-angiotensin system (RAS) inhibitors, following which proteinuria successfully decreased or disappeared. Their median eGFR was also stable, 53.3 mL/min/1.73 m2. CONCLUSIONS: As few symptoms can lead to OMN discovery, most patients were found during urine screening at school. Kidney dysfunction was observed in all patients at the time of kidney biopsy. Proteinuria has been significantly reduced and the decline rate of eGFR might be improved by RAS inhibitors. "A higher resolution version of the Graphical abstract is available as Supplementary information".

Clinical, Pathological, and Genetic Characteristics in Patients with Focal Segmental Glomerulosclerosis.

Background: Approximately 30% of children with steroid-resistant nephrotic syndrome (SRNS) have causative monogenic variants. SRNS represents glomerular disease resulting from various etiologies, which lead to similar patterns of glomerular damage. Patients with SRNS mainly exhibit focal segmental glomerulosclerosis (FSGS). There is limited information regarding associations between histologic variants of FSGS (diagnosed using on the Columbia classification) and monogenic variant detection rates or clinical characteristics. Here, we report FSGS characteristics in a large population of affected patients. Methods: This retrospective study included 119 patients with FSGS, diagnosed using the Columbia classification; all had been referred to our hospital for genetic testing from 2016 to 2021. We conducted comprehensive gene screening of all patients using a targeted next-generation sequencing panel that included 62 podocyte-related genes. Data regarding patients' clinical characteristics and pathologic findings were obtained from referring clinicians. We analyzed the associations of histologic variants with clinical characteristics, kidney survival, and gene variant detection rates. Results: The distribution of histologic variants according to the Columbia classification was 45% (n=53) FSGS not otherwise specified, 21% (n=25) cellular, 15% (n=18) perihilar, 13% (n=16) collapsing, and 6% (n=7) tip. The median age at end stage kidney disease onset was 37 years; there were no differences in onset age among variants. We detected monogenic disease-causing variants involving 12 of the screened podocyte-related genes in 34% (40 of 119) of patients. The most common genes were WT1 (23%), INF2 (20%), TRPC6 (20%), and ACTN4 (10%). The perihilar and tip variants had the strongest and weakest associations with detection of monogenic variants (83% and 0%, respectively; P<0.001). Conclusions: We revealed the distributions of histologic variants of genetic FSGS and nongenetic FSGS in a large patient population. Detailed data concerning gene variants and pathologic findings are important for understanding the etiology of FSGS.

Epidemiology of biopsy-proven Henoch-Schönlein purpura nephritis in children: A nationwide survey in Japan.

BACKGROUND: Little is known about the epidemiology of Henoch-Schönlein purpura nephritis (HSPN). METHODS: We conducted a nationwide epidemiological survey of Japanese children aged 1 to 15 years with HSPN. Children who were newly diagnosed with HSPN by biopsy between January 2013 and December 2015 were eligible for the survey to clarify the incidence of HSPN. We also conducted an institutional survey on kidney biopsy criteria and treatment protocols. RESULTS: A total of 353 of 412 institutions (85.7%) responded to the questionnaire. Of the 353 institutions, 174 reported to perform kidney biopsies at their institutions, and 563 children were diagnosed with HSPN. Considering the collection rate, the estimated incidence of biopsy-proven HSPN was 1.32 cases/100,000 children per year. The median age at biopsy was 7.0 years, and the male-to-female ratio was 1.2:1. The kidney biopsy criteria and treatment protocols for HSPN were as follows. Patients with acute kidney injury underwent biopsy at least one month after onset. For patients without kidney dysfunction, the timing for biopsy was determined by the amount of proteinuria. Regarding the treatment of HSPN, there were certain commonalities among the treatment protocols, they eventually differed depending on the institutions involved. CONCLUSIONS: The incidence of biopsy-proven HSPN was 1.32 cases/100,000 children per year in Japan. The male-to-female ratio and date of diagnosis of HSPN were similar to those in previous studies. The kidney biopsy criteria and treatment protocols for HSPN varied among institutions. Further studies are warranted to establish an optimal treatment policy based on the prognosis.

Efficacy of combination therapy for childhood complicated focal IgA nephropathy.

BACKGROUND: Patients with immunoglobulin A nephropathy who present with focal mesangial proliferation (focal IgAN) can have a relatively good prognosis, and renin-angiotensin system inhibitor (RAS-i) is commonly used as the initial treatment. However, there are some complicated focal IgAN cases with resistance to RAS-i treatment or nephrotic-range proteinuria. Thus, combination therapy including corticosteroids is often used. This study aimed to evaluate the efficacy of combination therapy for complicated focal IgAN cases by comparing to diffuse mesangial proliferation (diffuse IgAN). METHODS: We conducted a multicenter retrospective study on 88 children who received 2-year combination therapy. The participants were classified based on pathological severity: focal IgAN (n = 26) and diffuse IgAN (n = 62). RESULTS: In total, 26 patients with focal IgAN and 52 with diffuse IgAN achieved proteinuria disappearance within 2 years (100 vs. 83.9%, P = 0.03). Moreover, the time to proteinuria disappearance was significantly shorter in the focal IgAN group than in the diffuse IgAN group (2.9 vs. 4.2 months, P < 0.01) and all patients with focal IgAN achieved proteinuria disappearance within 8 months. At the last observation (8.6 vs. 10.4 years, P = 0.13), only patients with diffuse IgAN (n = 12) had greater than stage 2 chronic kidney disease. In terms of irreversible adverse events, one patient exhibited cataracts. CONCLUSION: Combination therapy was significantly effective in patients with complicated focal IgAN. Moreover, the long-term prognosis was good, and the duration of combination therapy for complicated focal IgAN can be decreased to reduce adverse events.

Use of renin-angiotensin system inhibitors as initial therapy in children with Henoch-Schönlein purpura nephritis of moderate severity.

BACKGROUND: Cases of Henoch-Schönlein purpura nephritis (HSPN) with moderate severity were demonstrated to achieve good prognosis after treatment with renin-angiotensin system (RAS) inhibitors. However, some patients required additional treatment for recurrence after remission. This study aimed to clarify the effect of RAS inhibitors in HSPN cases with moderate severity, including the proportion of cases with recurrence and their response to additional treatment. METHODS: Among 126 patients diagnosed with HSPN between 1996 and 2019, 71 patients with clinicopathologically diagnosed HSPN of moderate severity, defined as ISKDC grade II-IIIa and serum albumin ≥ 2.5 g/dL, were investigated. RESULTS: Proteinuria became negative after RAS inhibitor treatment alone in all 71 cases. However, 16 (22.5%) had recurrence. Eleven recurrent cases achieved negative proteinuria again following additional treatment. At the last follow-up (median 46.5 months; IQR, 23.2-98.2), 5 patients had persistent mild proteinuria; no patients had estimated glomerular filtration rate < 90 mL/min/1.73 m2. The pathological findings in all recurrent cases were ISKDC grade IIIa. The 16 recurrent cases had significantly higher proportions of glomeruli with global/segmental sclerosis (25.0 vs. 0%, P < 0.001) and tubular atrophy/interstitial fibrosis (37.5 vs. 12.7%, P =0.0 24) than 55 cases without recurrence. CONCLUSIONS: Japanese childhood HSPN cases with moderate severity had good outcomes without need for corticosteroids or immunosuppressants, when prescribed RAS inhibitor treatment. Even in recurrent cases, abnormal proteinuria was transient, and prognosis was excellent. A higher resolution version of the Graphical abstract is available as Supplementary information.

Influenza virus vaccination in pediatric nephrotic syndrome significantly reduces rate of relapse and influenza virus infection as assessed in a nationwide survey.

Although vaccination may precipitate relapses of nephrotic syndrome (NS) in children with idiopathic NS, no data are available regarding NS activity regarding influenza (flu) virus infections and NS relapses after receiving inactivated flu vaccines. We conducted a nationwide study of children aged 6 months to 15 years with idiopathic NS to assess the relationship between NS relapse, flu vaccination, and flu infections. We used a multivariate Poisson regression model (MPRM) to calculate the risk ratio (RR) for flu infection and for NS relapse in children with and without flu vaccination. Data of 306 children were assessed. The MPRM in all 306 children showed a significantly lower RR for flu infection (RR: 0.21, 95% confidence interval CI 0.11-0.38) and for NS relapse (RR: 0.22, 95% CI 0.14-0.35) in children receiving flu vaccination compared with unvaccinated children. In an additional MPRM only among 102 children receiving flu vaccination, they had a significantly lower risk for NS relapse during the post-vaccination period (RR: 0.31. 95% CI 017-0.56) compared with the pre-vaccination period. Although our study was observational, based on the favorable results of flu vaccinations regarding flu infections and NS relapse, the vaccine may be recommended for children with NS.

Utility of glomerular Gd-IgA1 staining for indistinguishable cases of IgA nephropathy or Alport syndrome.

BACKGROUND: Pathological findings in Alport syndrome frequently show mesangial proliferation and sometimes incidental IgA deposition, in addition to unique glomerular basement membrane (GBM) changes including thin basement membrane and/or lamellation. However, similar GBM abnormalities are also often observed in IgA nephropathy. Both diseases are also known to show hematuria, proteinuria, and sometimes macrohematuria when associated with viral infection. Therefore, it can be difficult to make a differential diagnosis, even based on clinical and pathological findings. Some recent articles demonstrated that galactose-deficient IgA1 (Gd-IgA1)-specific monoclonal antibody (KM55) could potentially enable incidental IgA deposition to be distinguished from IgA nephropathy. METHODS: We performed comprehensive gene screening and glomerular Gd-IgA1 and type IV collagen α5 chain immunostaining for five cases with both IgA deposition and GBM changes to confirm that Gd-IgA1 can help to distinguish these two diseases. RESULTS: Four of the cases were genetically diagnosed with Alport syndrome (Cases 1-4) and one was IgA nephropathy with massive GBM changes, which had a negative gene test result (Case 5). In Cases 1-4, glomerular Gd-IgA1 deposition was not detected, although there was positivity for IgA in the mesangial area. In Case 5, glomerular Gd-IgA1 deposition was observed. CONCLUSION: Gd-IgA1 expression analysis could clearly differentiate these two disorders. This approach can be applied to identify these two diseases showing identical clinical and pathological findings.

Non-immunosuppressive therapies for childhood IgA nephropathy.

IgA nephropathy (IgAN) is the most common chronic primary glomerulonephritis in both children and adults, and 20-30% of patients with persistent hematuria/proteinuria progress to kidney failure within 20 years. In Japan, most cases of childhood IgAN are detected by school screening programs during the early onset of the disease when hematuria/proteinuria are asymptomatic and kidney function is normal. Therefore, it is possible to follow the detailed clinical course and appropriate therapeutic interventions from early onset of the disease. Data on non-immunosuppressive therapies for children with IgAN are highly limited. The Japanese Pediatric IgA Nephropathy Treatment Study Group was organized in 1989 to conduct clinical trials and accumulate data on treatments for childhood IgAN. In this review, we focus on non-immunosuppressive therapies, notably with renin-angiotensin-aldosterone system (RAAS) inhibitors for childhood IgAN and related clinical trials conducted primarily in Japan. We also describe the anti-inflammatory and antiproteinuric effects of RAAS inhibitors in IgAN, differences in treatment regimens because of the acute and active pathological features of childhood IgAN, adverse events of RAAS inhibitors, other non-immunosuppressive treatment options, and future directions.

Prognosis and acute complications at the first onset of idiopathic nephrotic syndrome in children: a nationwide survey in Japan (JP-SHINE study).

BACKGROUND: Information on the epidemiology of idiopathic nephrotic syndrome (INS) in children, complications of INS and the side effects of steroid therapy is scarce. METHODS: The Japanese Pediatric Survey Holding Information of Nephrotic Syndrome, a nationwide cohort study, was conducted by the Japanese Study Group of Renal Disease in Children and enrolled 2099 children with newly diagnosed INS between 1 January 2010 and 31 December 2012. We conducted a follow-up study of the complications during the first onset and the patients' prognosis in this cohort. RESULTS: We obtained follow-up data on 999 children (672 males) with a median age at onset of 4.5 years [interquartile range (IQR) 2.8-9.4] and a median follow-up period of 4.1 years (IQR 2.5-5.1). At the first onset, 24% of patients experienced severe acute kidney injury (AKI), defined as a serum creatinine increase to a level two or more times the baseline. On logistic regression analysis, age, hematuria, severe hypoalbuminemia (serum albumin <1.0 g/dL) and severe bacterial infection were not independent factors, but female sex {hazard ratio [HR] 1.5 [95% confidence interval (CI) 1.1-1.7]} and hypertension [HR 4.0 (95% CI 2.6-6.0)] were significantly related to AKI. During the observation period, ocular hypertension requiring treatment occurred in 17.4% of patients, among which 0.4% received surgical treatment. Progression to frequently relapsing nephrotic syndrome/steroid-dependent nephrotic syndrome in 3 years was seen in 44.2% of the patients and was shown by the Cox regression analysis to be significantly related to younger age and days until remission at the first episode, but not to sex, hematuria, the minimum serum albumin level or AKI. Two patients died during the observation period. One patient showed progression to end-stage kidney disease. CONCLUSION: Based on the results of a multicenter questionnaire survey, the overall survival and renal survival rates were found to be excellent. However, proper management of complications, particularly in AKI and ocular hypertension, is mandatory.

Clinicopathological significance of glomerular capillary IgA deposition in childhood IgA nephropathy.

BACKGROUND: IgA nephropathy (IgAN) is characterized by predominant mesangial IgA deposition. Some patients with IgAN demonstrate IgA deposition in glomerular peripheral capillaries (cap-IgA). The clinicopathological significance of cap-IgA remains incompletely investigated in children. METHODS: We retrospectively analyzed 503 consecutive cases of biopsy-proven childhood IgAN between July 1976 and June 2013 to compare clinical and pathological features between IgAN patients with and without cap-IgA. RESULTS: Among the 503 patients, 30 (6.0%) had cap-IgA. We found significant differences in proteinuria (2.0 vs. 0.5 g/day/m2, p < 0.0001), time from onset to kidney biopsy (2.2 vs. 8.3 months, p < 0.0001), and rate of proteinuria remission after treatment (23.3% vs. 48.0%, p = 0.007) between both groups. Pathological analysis revealed significant differences in M1 (83.3% vs. 56.0%, p = 0.002), ratio of subendothelial electron dense deposits (EDDs, 58.6% vs. 16.5%, p < 0.0001) and subepithelial EDDs (48.3% vs. 16.5%, p = 0.0001), and glomerular basement membrane (GBM) lysis (58.6% vs. 27.1%, p = 0.0006) between both groups. More than half of cap-IgA patients (17/30, 56.7%), whereas only 26.2% of non-cap-IgA patients (124/473), were treated with immunosuppressive treatments. Six of 30 cases (20%) with cap-IgA reached glomerular filtration rate (GFR) categories G3a-G5 (estimated GFR < 60 ml/min/1.73 m2) at most recent observation (mean observation period: 7.0 ± 4.0 years). According to Kaplan-Meier analysis, patients with cap-IgA had significantly lower kidney survival curves than non-cap-IgA patients (72.8% vs. 97.2% at 10 years, p < 0.0001). CONCLUSIONS: Cap-IgA is associated with acute inflammation with GBM changes, resulting in refractory heavier proteinuria. Cap-IgA may represent a poor prognostic factor.