Reference values for urinary protein, albumin, beta 2-microglobulin, and the alpha 1-microglobulin-to-creatinine ratio in Japanese children.

BACKGROUND: The importance of the ratio of creatinine to urinary protein, albumin, and low-molecular weight protein as a urinary marker in chronic kidney disease patients is widely recognized. However, no reference values have hitherto been established for these markers in Japanese children. The present study aimed to establish the reference values for these urinary markers in Japanese children. METHODS: The first morning urine was randomly collected from 1712 pupils aged ≥ 3 to < 18 years during school and kindergarten mass urinary screenings. The upper limit of the reference values was set at the 97.5th percentile of the creatinine ratio per marker. RESULTS: The urinary protein-to-creatinine ratio (PCR), urinary albumin-to-creatinine ratio (ACR), urinary beta 2-microglobulin-to-creatinine ratio (BMCR), and urinary alpha 1-microglobulin-to-creatinine ratio (AMCR) showed an age-related decrease at the 50th percentile reflecting an age-related increase in urinary creatinine. The appropriate reference value for the PCR and ACR was 0.12 g/gCr and 35 mg/gCr, respectively, in the entire cohort. The appropriate reference value for the BMCR was 0.5 µg /mgCr for age ≥ 3 to < 6 years and 0.35 µg/mgCr for age 6 years or older. The appropriate reference value for the AMCR was 5.0 µg/mgCr for age ≥ 3 to < 6 years and 3.5 µg /mgCr for age 6 years or older. CONCLUSION: The present study was the first to determine appropriate reference values for the PCR, ACR, BMCR, and AMCR based on an analysis of the first morning urine samples of a large number of children.

Comprehensive genetic screening for vascular Ehlers-Danlos syndrome through an amplification-based next-generation sequencing system.

Vascular Ehlers-Danlos syndrome (vEDS) is a hereditary connective tissue disorder (HCTD) characterized by arterial dissection/aneurysm/rupture, sigmoid colon rupture, or uterine rupture. Diagnosis is confirmed by detecting heterozygous variants in COL3A1. This is the largest Asian case series and the first to apply an amplification-based next-generation sequencing through custom panels of causative genes for HCTDs, including a specific method of evaluating copy number variations. Among 429 patients with suspected HCTDs analyzed, 101 were suspected to have vEDS, and 33 of them (32.4%) were found to have COL3A1 variants. Two patients with a clinical diagnosis of Loeys-Dietz syndrome and/or familial thoracic aortic aneurysm and dissection were also found to have COL3A1 variants. Twenty cases (57.1%) had missense variants leading to glycine (Gly) substitutions in the triple helical domain, one (2.9%) had a missense variant leading to non-Gly substitution in this domain, eight (22.9%) had splice site alterations, three (8.6%) had nonsense variants, two (5.7%) had in-frame deletions, and one (2.9%) had a multi-exon deletion, including two deceased patients analyzed with formalin-fixed and paraffin-embedded samples. This is a clinically useful system to detect a wide spectrum of variants from various types of samples.

Urine alpha 1-microglobulin-to-creatinine ratio and beta 2-microglobulin-to-creatinine ratio for detecting CAKUT with kidney dysfunction in children.

BACKGROUND: The leading cause of advanced chronic kidney disease (CKD) in children is congenital anomalies of the kidney and urinary tract (CAKUT). However, the most appropriate parameters of biochemical urine analysis for detecting CAKUT with kidney dysfunction are not known. METHODS: The present observational study analyzed data on children with CAKUT (stage 2-4 CKD) and the general pediatric population obtained from school urine screenings. The sensitivity and specificity of urine alpha 1-microglobulin-, beta 2-microglobulin-, protein-, and the albumin-to-creatinine ratios (AMCR, BMCR, PCR, ACR, respectively) in detecting CAKUT with kidney dysfunction were compared with those of the conventional urine dipstick, and the most appropriate of these four parameters were evaluated. RESULTS: In total, 77 children with CAKUT and 1712 subjects in the general pediatric population fulfilled the eligibility criteria. Conventional dipstick urinalysis was insufficient due to its low sensitivity; even when the threshold of proteinuria was +/-, its sensitivity was only 29.7% for stage 2 and 44.1% for stage 3 CKD. Among the four parameters assessed, the AMCR and BMCR were adequate for detecting CAKUT in children with stage 3-4 CKD (the respective sensitivity and specificity of the AMCR for detecting CAKUT in stage 3 CKD was 79.4% and 97.5% while that of BMCR was 82.4% and 97.5%). These data were validated using national cohort data. CONCLUSION: AMCR and BMCR are superior to dipstick urinalysis, PCR, and ACR in detecting CAKUT with kidney dysfunction, particularly stage 3 CKD. However, for AMCR, external validation is required. A higher resolution version of the Graphical abstract is available as Supplementary information.

Identification of novel OCRL isoforms associated with phenotypic differences between Dent disease-2 and Lowe syndrome.

BACKGROUND: Although Lowe syndrome and Dent disease-2 are caused by Oculocerebrorenal syndrome of Lowe (OCRL) mutations, their clinical severities differ substantially and their molecular mechanisms remain unclear. Truncating mutations in OCRL exons 1-7 lead to Dent disease-2, whereas those in exons 8-24 lead to Lowe syndrome. Herein we identified the mechanism underlying the action of novel OCRL protein isoforms. METHODS: Messenger RNA samples extracted from cultured urine-derived cells from a healthy control and a Dent disease-2 patient were examined to detect the 5' end of the OCRL isoform. For protein expression and functional analysis, vectors containing the full-length OCRL transcripts, the isoform transcripts and transcripts with truncating mutations detected in Lowe syndrome and Dent disease-2 patients were transfected into HeLa cells. RESULTS: We successfully cloned the novel isoform transcripts from OCRL exons 6-24, including the translation-initiation codons present in exon 8. In vitro protein-expression analysis detected proteins of two different sizes (105 and 80 kDa) translated from full-length OCRL, whereas only one protein (80 kDa) was found from the isoform and Dent disease-2 variants. No protein expression was observed for the Lowe syndrome variants. The isoform enzyme activity was equivalent to that of full-length OCRL; the Dent disease-2 variants retained >50% enzyme activity, whereas the Lowe syndrome variants retained <20% activity. CONCLUSIONS: We elucidated the molecular mechanism underlying the two different phenotypes in OCRL-related diseases; the functional OCRL isoform translated starting at exon 8 was associated with this mechanism.

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.

Combination therapy with or without warfarin and dipyridamole for severe childhood IgA nephropathy: an RCT.

BACKGROUND: Two previous randomized controlled trials showed that treatment of severe childhood immunoglobulin A (IgA) nephropathy using prednisolone with azathioprine, heparin-warfarin, or dipyridamole prevented the increase of sclerosed glomeruli. Prednisolone alone, however, did not prevent further increase. These studies indicated the importance of immunosuppressants in the treatment. An additional pilot study using mizoribine instead of azathioprine enabled us to complete 2 years of combined regimen. It showed non-numerical inferior effectiveness compared with the azathioprine regimen. Further examination of the additional efficacy of warfarin and dipyridamole was required. METHODS: A randomized control trial of prednisolone and mizoribine with (group 1) or without (group 2) warfarin and dipyridamole was administered for treatment of 71 children with severe IgA nephropathy to evaluate the efficacy of additional warfarin and dipyridamole. RESULTS: Thirty of 34 patients (88.2%) in group 1, and 27 of 36 patients (75.0%) showed the disappearance of proteinuria as defined by early morning urinary protein to creatinine ratio of < 0.2 during the 2-year treatment period. The cumulative disappearance rate of proteinuria determined by the Kaplan-Meier method showed that the disappearance rate of proteinuria was significantly higher in group 1 than in group 2 (log-rank P = 0.04). There was no significant difference in pathological findings, but there was a tendency of increase of global sclerosis in group1 which might be related to warfarin. Most of the adverse effects were related to prednisolone, but fortunately transient. CONCLUSIONS: The balance between minimal benefits of warfarin/dipyridamole and potential adverse effects may be in favor of avoiding them in children with IgA nephropathy.

High incidence of idiopathic nephrotic syndrome in East Asian children: a nationwide survey in Japan (JP-SHINE study).

BACKGROUND: Little is known regarding the epidemiology of idiopathic nephrotic syndrome (INS) in East Asia. Previous studies have suggested higher incidence of INS in Asian children, though decreasing trend of its incidence has also been shown. METHODS: We conducted a nationwide study of Japanese children aged 6 months to 15 years with INS. Children who were newly diagnosed with INS between 1 January 2010 and 31 December 2012 were eligible. Children with congenital nephrotic syndrome or nephrotic syndrome secondary to nephritis were excluded. RESULTS: A total of 2099 children were initially diagnosed with INS and were followed for up to 4 years. The estimated incidence of INS was 6.49 cases/100,000 children per year, without clear correlation with geographical region. The male:female ratio was 1.9 and approximately 50 % of children were <5 years old at diagnosis. During the 1-4 years follow-up, 32.7 % developed frequently relapsing nephrotic syndrome and steroid-dependent nephrotic syndrome. CONCLUSIONS: Based on our nationwide survey, the incidence of INS in Japanese children is approximately 3-4 times higher than that in Caucasians. However, the male:female ratio and the age at onset were similar to those in previous studies. We are now planning a prospective cohort study to examine the course of INS in Japan.

Morbidity in children with frequently relapsing nephrosis: 10-year follow-up of a randomized controlled trial.

BACKGROUND: To investigate the long-term outcome in children with frequently relapsing nephrotic syndrome (FRNS) we conducted a follow-up of a previous randomized controlled trial (RCT) 10 years after the initiation of the treatment protocol. METHODS: We previously conducted an RCT on the efficacy of cyclosporine for treating children with FRNS. After 2 years of treatment, a recommended a management protocol of steroids, and immunosuppressants was provided. RESULTS: Valid information was available for 46 of the 56 patients (82.1 %) enrolled in the original RCT. The median follow-up period was 10.3 years from the start of protocol treatment with cyclosporine. At last follow-up (mean age 18.7 years), only ten patients (21.7 %) showed disease-free remission (no relapse for at least 2 years). In contrast, 23 (50.0 %) continued to relapse frequently or were on immunosuppressants, eight patients (17.4 %) had infrequent relapses without immunosuppressants. Adverse effects attributable to treatment included short stature (6 patients), osteoporosis (six patients), obesity (4 patients), cataracts (3 patients) and hypertension (3 patients). No lethal event or renal dysfunction occurred during follow-up. CONCLUSIONS: This 10-year follow-up study shows that most children with FRNS experience relapses after 2 years of cyclosporine treatment, in adolescence and into adulthood. Outcomes in terms of life expectancy and renal function are favorable.

Urinary screening and urinary abnormalities in 3-year-old children in Japan.

In Japan, urinary screening for preschool children has been obligatory since 1961. The system was reconsidered and has been under review since 2012, because many problems in the system had been identified, and its usefulness was uncertain. In the process, the following were analyzed: (i) frequency of urinary abnormalities identified on screening; (ii) diseases identified from urinary abnormalities; (iii) clinical course of children found to have urinary abnormalities; and (iv) screening for asymptomatic urinary tract infection (UTI) as a way of screening for congenital anomalies of the kidney and urinary tract. A computerized literature search was conducted, and study reports issued by the Ministry of Health, Labour and Welfare study group, and data of Akita City and Chiba City were reviewed. The prevalence of abnormal results at the first urinalysis was high, but at the second urinalysis the prevalence decreased in the range 1/6-1/20. The prevalence of tentative diagnosis at the third urinalysis was similar to the school urinary screening results. Serious illness was not found in children who had hematuria alone. In contrast, diseases requiring immediate attention were found in children with proteinuria, although the prevalence of proteinuria was not high. The dipstick method for leukocyturia was inefficient. The importance of two consecutive urinalyses before detailed examination, the lack of usefulness of screening for hematuria in 3-year-old children, and the importance of proteinuria were confirmed. Screening for asymptomatic UTI using urinary leukocytes was very inefficient.

Utility of High-b-Value Diffusion-Weighted Magnetic Resonance Imaging in Evaluating Reversible Medial Longitudinal Fasciculus Syndrome Caused by Acute Brainstem Ischemia.

BACKGROUND: Medial longitudinal fasciculus (MLF) syndrome refers to a gaze disorder characterized by impaired adduction on the ipsilateral side to the injured MLF, with dissociated nystagmus of the contralateral abducting eye. The most common cause of the MLF syndrome is ischemic stroke. However, acute ischemic change in the MLF may be undetectable even on diffusion-weighted magnetic resonance imaging (DW-MRI) partly because of its small size and specific brainstem location. CASE REPORT: Herein, we present the first reported case of MLF syndrome in which, compared with the standard-b-value DWI, a higher b-value DWI revealed more clearly a small infarction in the dorsal pons in the acute stage. CONCLUSIONS: We suggest that high-b-value DWI can be a useful diagnostic method for patients with MLF syndrome caused by possible brainstem ischemia and thus supportive for deciding the optimal treatment for such patients.

Japanese Dent disease has a wider clinical spectrum than Dent disease in Europe/USA: genetic and clinical studies of 86 unrelated patients with low-molecular-weight proteinuria.

Dent disease is an X-linked disorder characterized by low-molecular-weight (LMW) proteinuria, hypercalciuria, nephrocalcinosis, urolithiasis and renal dysfunction. Dent disease is caused by mutations in at least two genes, i.e. CLCN5 and OCRL1, and its genetic background and phenotypes are common among European countries and the USA. However, only few studies on Dent disease in Japan, which was originally called 'low-molecular-weight proteinuric disease', have been reported thus far. In this study, we analysed genetic background and clinical phenotype and laboratory data of 86 unrelated Japanese Dent disease patients. The results demonstrated that the genetic basis of Japanese Dent disease was nearly identical to those of Dent disease in other countries. Of 86 unrelated Japanese Dent patients, 61 possessed mutations in CLCN5 (Dent-1), of which 27 were novel mutations; 11 showed mutations in OCRL1 (Dent-2), six of which were novel, and the remaining 14 patients showed no mutations in CLCN5 or OCRL1 (Dent-NI). Despite the similarity in genetic background, hypercalciuria was detected in only 51%, rickets in 2% and nephrocalcinosis in 35%. Although the patients were relatively young, six patients (8%) showed apparent renal dysfunction. Japanese Dent disease has a wider clinical spectrum than Dent disease in Europe and the USA.

Clinical significance of cerebrospinal fluid presepsin as adjunctive biomarker for postneurosurgical meningitis: A single-center prospective observational study.

Background: Postneurosurgical meningitis (PNM) is a serious complication in neurocritical care patients, leading to clinical deterioration and worsening outcomes. Accurate diagnosis of PNM is often difficult due to the lack of definitive diagnostic criteria. This study investigates the potential utility of cerebrospinal fluid (CSF) presepsin (PSP), blood PSP, and the CSF/blood PSP ratio as adjunctive biomarkers for the diagnosis of PNM. Methods: We conducted a single-center prospective observational study at Nara Prefecture General Medical Center in Nara, Japan, from April 2020 to March 2022. The postoperative neurosurgical patients with suspected PNM were included in the study and divided into PNM and non-PNM groups. We evaluated the sensitivity, specificity, area under curves (AUCs), positive predictive value (PPV), and negative predictive value (NPV) for the diagnosis of PNM with CSF PSP, blood PSP, and CSF/blood PSP ratio compared in the two groups. Results: We screened 241 consecutive patients with postoperative neurosurgery. Diagnosis of PNM was suspected in 27 patients, and the clinical diagnosis was confirmed in nine patients. The results of CSF PSP (cutoff: 736 pg/mL) for the diagnosis of PNM were sensitivity 89%, specificity 78%, PPV 67%, NPV 93%, AUC 0.81 (95% confidence interval [CI], 0.60-1.00), blood PSP (cut-off: 264 pg/mL) was 56%, 78%, 56%, and 78%, 0.65 (95% CI, 0.42-0.88), and those of CSF/blood PSP ratio (cutoff: 3.45) was 89%, 67%, 57%, and 92%, 0.83 (95% CI, 0.65-1.00). Conclusion: Elevated CSF PSP and CSF/blood PSP ratio may be associated with PNM and could serve as valuable adjunctive biomarkers for improving diagnostic accuracy.

Prospective 5-year follow-up of cyclosporine treatment in children with steroid-resistant nephrosis.

BACKGROUND: Cyclosporine has improved remission rates in children with steroid-resistant nephrotic syndrome (SRNS). However, little prospective long-term follow-up data is available. METHODS: We prospectively followed and analyzed 5-year outcomes of all 35 patients enrolled in our previous prospective multicenter trial with cyclosporine and steroids in children with SRNS. At enrollment, 23 cases were classified as minimal change (MC), five as diffuse mesangial proliferation (DMP), and seven as focal segmental glomerulosclerosis (FSGS). RESULTS: Renal survival at 5 years (median 7.7 years) was 94.3 %. Patient status was complete remission (CR) in 31 (88.6 %) (MC/DMP, 25; FSGS, 6); partial remission in one (FSGS); and non-remission in three (MC/DMP), including chronic kidney disease and end-stage kidney disease in one each. Among 31 patients with CR, 22 (71.0 %) were receiving treatment with immunosuppressants at 5 years, including cyclosporine in 19, and seven of these 22 continued to show frequent relapse. Response to cyclosporine at 4 months predicted 5-year outcome in 31 of 35 patients. CONCLUSIONS: Although SRNS treatment with cyclosporine provides high renal survival and remission rates, many children require ongoing immunosuppression. Management has advanced from the prevention of end-stage kidney disease to the long-term maintenance of remission and management of relapse after induction therapy.

Establishment of a normal reference value for serum ß2 microglobulin in Japanese children: reevaluation of its clinical usefulness.

OBJECTIVE: Serum ß2 microglobulin (ß2MG) is considered to be a marker of renal function, which is independently associated with age. However, only a few studies have reported the reference values for ß2MG in children thus far, particularly in young children. In this study, we evaluated the distribution of serum ß2MG values in healthy Japanese children and assessed its clinical usefulness. METHOD: The normal reference value of serum ß2MG was assessed in serum samples from 1131 normal Japanese children (504 boys and 627 girls; age 0-17 years). To test the validity of the reference value, serum samples from children with various kidney diseases were also examined retrospectively. RESULTS: The mean values for ß2MG were significantly negatively correlated with age (r = -0.47, P < 0.001). No significant difference was observed between the values of boys and girls in any age group. The established ß2MG reference range covered 99.7 % of patients with decreased kidney function below 75 % based on their serum creatinine (Cr) value and body length. CONCLUSION: The newly established ß2MG reference value in children can be used to detect kidney impairment in children. Serum ß2MG in combination with serum Cr used as markers for predicting glomerular function can provide an accurate detection of kidney dysfunction in children.

Reference ranges for serum cystatin C measurements in Japanese children by using 4 automated assays.

OBJECTIVE: The data available on reference ranges for cystatin C in children are limited, and there are discrepancies among the available data. The aim of this study was to describe the reference ranges for cystatin C in Japanese children by using 4 automated assays. METHODS: Serum cystatin C levels were measured in 1128 Japanese children aged 3 month to 16 years without kidney disease. We calculated age-, gender-, race- and assay-specific cystatin C ranges. RESULTS: For all 4 assays, the median serum cystatin C levels were raised in term infants compared with older children and decreased by the first 2 years. The median serum cystatin C levels remained constant throughout up to the age of 14 years and decreased in children aged 15-16 years. The median serum cystatin C levels in children aged 12-16 years were slightly higher in males than in females. Assay-specific differences were also observed in the levels of serum cystatin C measured. CONCLUSION: Age-, gender-, race- and assay-specific ranges for serum cystatin C should be used as another tool to assess kidney function in children.

[A case of esophageal cancer with a funnel chest].

Esophageal cancer is a disease that is difficult to manage before and after surgery and is associated with a high in-hospital mortality rate despite there being reports of improved outcomes after multidisciplinary treatment. Meanwhile, although funnel chest is generally a subclinical condition, patients with this deformity may sometimes present with cardiac failure and chest pain. We report a case of advanced esophageal cancer with a funnel chest deformity that was very difficult to reconstruct after thoracoscopy-assisted resection.

Is the new Schwartz equation derived from serum creatinine and body length suitable for evaluation of renal function in Japanese children?

UNLABELLED: The present study was performed to determine whether the new Schwartz "bedside" equation can be used to estimate the glomerular filtration rate (GFR) in Japanese children as there are differences in renal function and muscle mass between Japanese and American individuals. It is also important to determine whether one common equation can be used in children from 1 to 16 years old, including the period of adolescence. Blood samples were collected from a total of 1,074 healthy children (466 males and 608 females) between 1 and 16 years old. The estimated GFR (eGFR) derived by the new Schwartz bedside formula [eGFR (in milliliters per minute per 1.73 m(2)) = 0.413 × body length (in centimeters)/serum Cr value (in milligrams per deciliter)] was calculated in all subjects, and the relationship between age and eGFR was analyzed. The eGFR decreased gradually with age, and the decrease was more marked in males than females, mainly in adolescence. Weak negative but significant correlations were observed in 466 males and 608 females. The median of the eGFR value showed a gradual significant decrease with age. CONCLUSION: A common coefficient cannot be used in children between 1 and 16 years old, including the period of adolescence, with the Schwartz type formula, and the new Schwartz bedside formula cannot be used when we estimated GFR in Japanese children. It is necessary to establish an eGFR equation specifically for Japanese children.

Non-occlusive mesenteric ischemia during acute stroke management: three case reports.

BACKGROUND: There are many reports of non-occlusive mesenteric ischemia in patients on maintenance hemodialysis and following cardiac surgery. However, there are few reports of non-occlusive mesenteric ischemia in patients with acute stroke. CASE PRESENTATION: We report three cases of non-occlusive mesenteric ischemia with onset during treatment for acute stroke. All of the patients were undergoing strict blood-pressure control, and two patients developed NOMI soon after tracheostomy when enteral nutrition had been resumed. CONCLUSION: Many stroke patients are older adults with risk factors such as arteriosclerosis. Thus, during acute stroke management, there is a possibility that patients may develop non-occlusive mesenteric ischemia due to decreased intestinal blood flow secondary to strict blood-pressure control. This case report implicates early enteral nutrition as a potential etiopathogenic factor of non-occlusive mesenteric ischemia in patients with acute stroke.

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.